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Full text of "The embryology and metamorphosis of the Macroura"

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NATIONAL ACAI3EMY OF SCIENCES. 



VOL. V. 



FOURTH INFEMOIR. 



THE EMBRYOLOGY AND METAMOmiOSIS OF THE MACIIOURA. 




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T H E 



EMBRYOLOGY AND METAMORPHOSIS 



OF THE 



MAGROURA. 



BY 



PROFESSOli OF ANIMAL MORPHOLOGY IN THE JOHNS HOPKINS UNn'ERSITY 



AXD 



PROFESSOR OF BIOLOGY IN ADELBERT COLLEGE, 

LATE FELLOW IN THE JOHNS HOPKINS UNIVERSITY. 



WITH FIFTY-SEV-EN PI.ATE8. ,, ^ 

S. Mis. 94 21 



CONTENTS. 



I. iDtrodiictioii. 
11. The life history of Stenopiis hispiiliis. 

Scc-tioii 1. Nutiiral history of .Steuopiis. 
Section 2. Sogmeiitiilion uiiil the early staf;e». 
Section 3. Metamorphosis of the larva. 
Section 4. The adult. 
Remarks. 
List of species. 
Literature of Stonopus. 
IlL The habits and metamorphosis of Gouodactylus chi- 
raj^ra. 

Section 1. The structure and habits of the adult. 
Section 2. Metamorphosis. 

IV. The metamorphosis of Alpheus. 

Section 1. The metamorphosis of Alpbeus minos. 
Section 2. The metamorphosis of Alpheus hete- 

rochelis iu the Bahama Isl.iuds. 
Sections. The metamorphosis of Alpheus bete- 

rochelis at Beaufort, North Carolina. 
Section 4. The metamorphosis of Alpheus hote- 

rochelis at I^ey West, Florida. 
Section .'>. The larval development of Alpheus 

saulcyi. 

V. Alpheus : A study in the development of the Crus- 

tacea. 
Introduction. 
Methods. 
I'AitT First. 

Section 1. The habits and color variations of 
Alpheus. 

[With fifty 



I'aut Fir.st — Continued. 

Section 'i. Variations in Alpheus heterochelis. 

Section :i. The abbreviated development of 
Alpheus and its relation to the environment. 

Section 4. The adult. 

Section 5. Variations from the specific type. 

Section (>. MeasHrements. 

Section 7. The causes and significance of varia- 
tion in Alpheus saulcyi. 
Part Second. 

Development of Alpheus. 

Section 1. Structure of the larva of Alpheus 
saulcyi. 

Section 2. The origin of ovarian eggs in Al|theus, 
Homarus, and Paliuurus. 

Section '3. Segmentation in Alpheus mines. 

Section 4. The embryology o^ Alpheus. Stages 
1-13. 

Section .'i. Notes on the segmentation of Crusta- 
cea. 

Section G. Cell degeneration.' 

Section 7. The origin and history of wandering 
cells iu Alpheus. 

Section 8. The development of the nervous sys- 
tem. 

Section 9. The eyes. 

Section 10. Summary. 

Section 11. References. 
Explanation of figures (accompanying each plate). 



-seven plates.] 



323 



f^f^:r 



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CHAPTER I. -'^''^^tacsg 

INTRODUCTION. 



By W. K. Brooks. 



No great group of auimals is more favorable than the Crustacea for the study of the history 
and significance and origin of larval forms, for these animals possess a number of peculiaritii'S 
which serve to render the problem of their life histt>ry both unusually interesting and significant, 
and at the same time unusually intelligible; nor are these peculiar features exhibited, to the 
same degree, by any other great group of animals. 

The body of an arthropod is completely covered, down to the tip of each microscopic hair, 
bj- a continuous shell of excreted matter, and afs this chitinous shell is not cellular it can not grow 
by the interpolation of new cells, nor can it, like the excreted shell of a moUusk grow by the dep- 
osition of new matter around its edges, for there are no such growing edges, except in a few 
exceptional cases, such as the barnacles. Once formed and hardened the cuticle of an arthroi)od 
admits no increase in size, and as soon as it is outgrown it must be discarded and replaced by a 
new and larger one. The new shell is gradually excreted, in a soft condition, under tlie old one, 
and as soon as this is thrown oft" the new one quickly becomes fully distended and solid. As a 
result, from the very nature of the chitinous shell and the method of renewal which its structure 
entails, the growth of an arthropod, from infancy to the adult condition, takes place by a series of 
well marked steps or stages, each one characterized by the formation of a new cuticle and by a 
sudden increase in size. 

In most arthropods the newly-born young are very dift'erent in structure from the adults, and 
growth is accompanieil by metamorphosis. As the changes of structure are. necessarily confineil 
to the moulting i)eriods, the stages of growth coincide with the stages of change in organization, and 
there is none of the indefiniteness which often characterizes the dift'erent larval stages of animals 
with a more continuous metamorphosis. On the contrary the nature of each change is as shari)ly 
defined and as characteristic as the structure of the adult itself. As the moulting period is fre 
quently a time of inactivity the animal may then undergo profound changes without inconvenience, 
and the successive stepsin the metamorphosis of an arthropod are not only well marked, but often 
very profound as well. 

In these features all the other arthropods are like the Crustacea, but another consideration, 
the fact that, with few exceptions, the higher Crustacea are marine, renders the problem of their 
life history much more intelligible than that of any other class of auimals. 

So far as the ontogenetic history of the metamorphosis of a larva is a recapitulation of ances- 
tral stages iu the evolution of the species its retention at the present day must depend to a great 
degree upon the persistency of those external conditions to which the larval stages were originally 
adapted. 

This is true at least of all free larvae, which have their own battle to fight an<l their own living 
to get, and while a larva inside an egg or within a brood pouch may possibly recapitulate obsolete 
ancestral stages, the survival of a free larva depends upon its a<laptation to its present environ- 
ment. 

As compared with the ocean the inorganic environment of terrestrial or fresh- water animals 
is extremely variable, and changes in climate, elevation, and continental configuration are accom- 
panied by corresponding changes in enemies, competitors, and food, so that the conditions which 

325 



326 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 

surround a modern terrestrial larva must, in nearly every case, be very different from those under 
whicb the remote ancestors of the species passed their life, but while this is also true, to some 
degree, of marine animals their inorganic environment is comparatively stable, and tlie persistence 
of so many ancient marine types shows that the changes m the organic surroundings of marine 
animals take place much more slowly than corresponding changes on land. 

This fact, joined to the definite character of the changes which make up the life history of a 
marine crustacean, renders these animals of exceptional value for the study of the laws of larval 
development, and for the analysis of the effect of secondary adaptations, as distinguished from the 
influence of ancestry ; for while Glaus has clearly iiroved that adaptive larval forms are much 
more common among the Decapods than had been supposed, his writings and those of Fritz Muller 
show that no other group of the animal kingdom presents an equal diversity of orders, families, 
genera, and species in which the relation between ontogeny and phylogeny is so well displayed, 
but, while proving this so clearly, Glaus' well known monograph also shows with equal clearness 
that this ancestral history is by no means unmodified, and that the true significance of the 
larval history of the higher Crustacea can be understood only after careful and minute and exhaus- 
tive comparison and analysis. 

Greatly impressed by this fact, I began nearly ten years ago to improve the opportunities 
that were ofl'ered by the marine laboratory of the Johns Hopkins University, for obtaining more 
complete and detailed knowledge of the larval stages of a number of Macroura, and this work has 
been prosecuted at every opportunity up to the present time. Some of my results have been pub- 
lished in my monograph on Lucifer, in the Phil. Trans. Eoyal Soc. for 1882, and others are incor- 
porated in my report on the Stomatopoda collected by H. M. S. Challenger. 

This memoir contains the life histories of a number of additional species based in part 
upon my own studies at Beaufort, North Carolina, and at Green Turtle Key and New Providence 
in the Bahama Islands, but chiefly upon the researches which one of my students, Mr. F. H. Her- 
rick, has carried on under my general supervision. In 1886 he undertook, at my suggestion, the 
study of the embryology and metamorphosis of the Macroura, and devoted three years to this sub- 
ject under my direction, and the results which follow are almost entirely due to his zeal and 
energy. He has completed the study of several subjects upon which I had previously made a 
beginning, so that my own unfinished notes have been incorporated with his researches, and our 
respective shares in the work are as follows: The chapter on Gonodactylus is entirely based upon 
my own researches; the chapter entitled '^Alphevs, a study in the development of the Crustacea," 
is entirely the work of Mr. Herrick ; tlie one on the metamorphosis of Alpheus is based upon our 
combined studies, and that upon Steuopus is almost entirely the work of Mr. Herrick, as my own 
contributions to this life history are of minor value except so far as they supplement his work. 

I shall now give a brief outline or summary of the chief results which are described in detail 
in each chapter. 

THE LIFE HISTORY OF STENOPUS HISPIDTJS. 

During the six seasons which I spent at Beaufort, North Carolina, I captured in the tow-net, 
at dift'erent times, some six or seven specimens of a remarkable pelagic crustacean larva, all of 
them well-advanced and in nearly the same stage of dev^elopment. 

Nothing was learned of the earlier larval life nor of the adult form of the animal, although 
enough was made out to show that it is one of the few Macroura which, like Peneus and the Ser- 
gestidiB, have retained the primitive or ancestral metamorphosis, and that its secondary modifica 
tions are very slight as compared with those of ordinary macrouran larvje, and also that the 
Beaufort larv* are new to science. (See Pis. ix and x.) 

These larva; have the full number of adult somites and appendages, and in side view they are 
very suggestive of the Sergestidie. They are very much larger than ordinar3' pelagic larvre and 
are quite different from any known forms of Macroura. 

The chief locomotor organs are the last pair of thoracic legs, which are extremely slender, as 
long as the entire body of the larva, ending in flattened elliptical paddles, which are used as 
sweeps for rowing through the water. They are stretched out in front of the body near the 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 327 

inidtlle line and are tben swept backwards and outwards, describing at each stroke a circle equal 
ill diameter to about twice the length of the body. By the vigorous use of these oars the larva 
skims rapidly through the water, and its movements are not unlike those of a Gerris.upon the 
surface of a fresh water pond. 

Notwithstanding the importance of a complete knowledge of the life history of the animal to 
which this sergestid-like larva belongs, I was unable to complete the study at Beaufort, although 
I made careful drawings of two stages and filed them away for future use. 

Immediately upon our arrival at Green Turtle Key, in the Bahama Islands, early in .hme, 
188G, our attention was at once attracted to a small, graceful, brilliantly colored i)rawu which was 
found in abundance among the coral. (See Fl. V.) It proved to be Stcnopun hinpidm, a species 
which is chiedy known to naturalists through specimens from the Indian and South Pacific oceans. 
It has l)een recorded as occurring in the tropical Atlantic, but our knowledge of the adult ha« been 
very scanty and imperfect, and nothing whatever has been known regarding its life history until 
Mr. Ilerrick devoted himself to its thorough investigation. 

It is an active, timid animal, and is one of the most brilliantly colored of the Crustacea. As 
it is also one of the most widely distributed, it is noteworthy that while its color markings are so 
prominent and conspicuous they are extremely well fixed and constant; so much so that the speci- 
mens from the Indian Ocean and the South Pacific agree with those from the West Indies down 
to the most minute markings. 

The adults are found in pairs, a male and a female swimming together side by side and exhib- 
iting evidence of strong conjugal attachment to each other. 

The most noteworthy fact in its history is its world-wide distribution, and the question whether 
this can be a result of any peculiarity in its structure or habits at once suggests itself. 

We should expect, on general jirinciples, to find the least specialized species the most widely 
diffused; and one which holds its ground in so many j)art8 of the world, and without any change 
of structure finds a safe and congenial home in seas so widely .separated, might be expected to be 
of indefinite or slightly specialized habits, but this is not the case. In structure, in habits, in color, 
and in external aiipearance, and also in its metamorphosis, Stenopus is one of the most highly 
specialized of the Crustacea; and it owes its abilitj' to survive in inauy seas to the accuracy and 
delicacy of its adjustment to a narrow range of conditions, rather than to indefinite and vague 
adaptation to many conditions. 

Its autennsie are unusually long and slender, and the acuteness of its senses, togf^ther with its 
very remarkable alertness; the <|uickness with which it perceives danger, and the raindity with 
which it escapes; have undoubtedly aided it in holding its own wherever it has gained a foothold 
in a suitable locality, and no crustacean, with the exception, possibly, of Gonodactylus chiagra, is 
better adapted for life in a coral reef. 

It is well protected from enemies by a thorny armor of hooked spines, which cover all the 
upper surface of its body and limbs, and as all the hooks point forward the attempt of an enemy 
to swallow a Stenopus must be difficult and painful. 

These facts no doubt account for its survival, and the length of its pelagic larval life is beyond 
question an aid to its wide disi^ersal and to the discovery of new homes. 

While we cannot state that the adult will not at some time be found ujmn the Atlantic coast of 
onr Southern States, there is no evidence that this is the case, and the larva? which were obtained 
at Beaufort, North Carolina, were undoubtedly hatched from eggs which were carried upon the 
abdominal appendages of parents in the West Indies or on the Florida Keys; and these larva- 
had therefore wandered more than six hundred miles from their birthplace. The species might 
therefore be dittused through a chain of coral islands six hundred miles apart, from a single start- 
ing point, in a very small number of generations. 

The eggs, which are very small, are laid at night, and the segmentation, which Professor 
Herrick has thoroughly studied by sections, is entirely confined to the nuclei, the yolk remaining 
undivided; Steuojius therefore presents a most pronounced type of centrolycethic segmentation. 

The great mass of the egg consists of a homogeneous mass of yolk granules, which takes no 
part in the process of segmentation and probably contains no iirotoplasm. This yolk is aggre- 
gated around a central nucleus, which divides, probably indirectly, into two, four, eight, sixteen 



328 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

nuclei and so on until the number is yery great. As this process of division goes on the nuclei, 
each with an investing layer of protoplasm, gradually migrate to the surface of the yolk, and at 
last form a superficial investing layer around a central yolk, out of which all the protoplasm has 
been withdrawn. 

The yolk does not divide up into typical yolk pyramids, although the outlines of the blasto- 
meres are 8har[)ly indicated by transitory superficial furrows. 

The embryonic area is soon marked out as a region where the nuclei are densely crowded, and 
the point of invagination is indicated by a solid ingrowth which penetrates the yolk to form the 
inner layers of the embryo. The subsequent stages of embryonic development were not followed 

in detail. 

The larva hatches in the afternoon, and during the following night the parent moults and lays 
another brood of eggs. 

At the time of its escape the larva is a Protozoea, and its later history is of great interest, since 
it unites features of resemblance to Lucifer, Sergestes, Peneus, and to the prawns in general, with 
individual peculiarities in which it differs from all of them. 

At the time of hatching (PI. vii and PI. XI, Fig. 25) it has sessile eyes, locomotor antennae, 
an enormous mandible, a deeply forked telsou, a long rostrum, and a complete series of append- 
ages as far as the first pereiopods, which are essentially like the third masillipeds. The long 
hind body has no appendages and is only vaguely divided into somites. 

Five or six hours after hatching it changes into a true zoea, much like that of an ordinary 
macrourau (PI. viii). The carapace becomes much enlarged ; the rostrum is shortened to less than 
half its former length, the mandible becomes small, the forks disappear from the telson, the eyes 
become stalked, the antennte are shortened like those of a zoea, and the maxillipeds become the 
chief locomotor organs. 

As these larvie could not be reared in captivity the later stages were studied from captive 
specimens, but Professor Herrick has proved that the Beaufort larvse are either young Stenopi or 
else the larvae of some closely allied species which is at present unknown, 

A specimen a little older than the oldest Beaufort specimen was captured at Nassau (PI. xii). 
It is in the Mastigopus stage, with greatly elongated eyes, and with antenna which are gradually 
approximating to those of the adult. The third maxillipeds are now extremely long and are the 
largest of all the limbs, while the huge, oar-like fifth pereiopod of the preceding stage is now 
reduced to a rudimentary bud, and the fourth is also reduced to a two-jointed rudiment. 

It thus appears that, as in the Sergestidw, the last two pairs of " walking legs " are shed .liter 
the Mysis stage, to be again reconstructed in the Mastigopus stage. After several moults the 
Mastigopus larva gradually assumes the adult form, the principal changes being the shortening 
of the eyes and the reacquisition of the fourth and fifth pereiopods. 

ALPHEUS. 

The genus Alpheus includes a large number of small, brilliantly colored crayfish-like Cru- 
stacea, which are widely distributed, although all are essentially tropical. Two species range 
as far northward as the coast of Virginia, but the true home of the genus is the warm water 
between tide-marks or near the shore in coral seas, and they occur in the greatest abundance 
and variety in all the sounds and inlets among coral islands. They are well adapted, in structure 
as well as in habits, for a life among the coral, and of all the Crustacea which abound upon the 
coral reefs the genus Alpheus is one of the most common and most thoroughly characteristic (PI. 
I, II, and IV). 

Nearly every mass of sponge or algie or of coral rock or living coral which is fished up from 
the bottom and broken to pieces contains specimens of one or more species of Alpheus, and pieces 
are often found which fairly swarm with these little animals. 

A few of the species wander over the bottom, and wandering individuals of other species are 
found occasionally, but their true home is in the tubes of sponges and the holes and crannies in 
the i>orous coral limestone, or under the broken shells and fragments of limestone which lie upon 



MEMOIRS OF THB NATIONAL ACADEMY OF SUIEXCES. 320 

tlic baUom ill sljiillow water. Occasionally they inhabit short, vertical burrows, which they con 
struct for themselves in the sandy mud, but most of the species pass their life bidden in the shelter 
\vhi(;li they liiul upon the reef. 

The most conspicuous characteristic of the genus is the great enlargement of the claws of the 
first pair of walking legs. P.oth claws are large, but one of them is euormous, and it serves as a 
most formidable weapon of often.sc and defense. In some species this large claw nearly equals 
the body in size, and it is usually carried stretched out in front of the body, but one species carries 
it folded down under the body and hidden, ready to be instantly i)uslied out to make a rai)id thrust 
at any enemy. 

In nearly all the sjjecies the large claw terminates in hard, jiowerful forceps. The claw or 
dactyle is provided with a plug, which Jits into a well or socket in the other joint and probably 
serves to prevent dislocation. When the forceps are opened the dactyle is raised so that the plug 
Just rests in the month of the scujket. As soon as the claw is released it is snddeidy and violently 
closed, as if by a spring, and the solid stony points striking together produce a sharp metallic 
report, something like the click of a water hammer, and so much like the noise of breaking glass 
that I have often, when awakened at night by the click of a little Aljilieus less than an inch long, 
hastene<l down to the laboratory in fear that a large aquarium had been broken. In the open 
water the report is not so loud as it is when the animals are confined in small aquaria, but Al- 
pheus is so abundant in all the Bahama Sounds that a constant fusilade is kept up at low water all 
along the shore. The animals are remarkably pugnacious and they will even attack bathers. They 
are known to the inhabitants of the out islands as "scorpions," and are much dreaded, although 
their atta(!ks are harmless to man. The snapping propensity is exhibited l)oth in the water and 
out by both sexes, and if two males or two females, either of the same or different species, are 
placed together in an aquarium, a most violent combat at once takes place, and quickly ends by' 
the destruction of one or both. Some species appear to pinch with the large (ilaw, but it is more 
frequently used like a saber for cutting a slashing blow. The edge of the movable joint is sharp 
and rounded, and the animal advances warily to the attack with the claw widely opened and 
stre^hed out to its full length. Watching its opportunity it springs suddenly upon its enemy, 
instantly closing its claw with a violent snap and a loud report, and cutting a vertical sweep with 
its sharp edge. I have often seen Alphetis heterochelis cut another com[)letely in two by a single 
blow, and the victim is then quickly dismembered and literally torn to fragments. 

The abundance of these animals in coral seas is well shown by th& fact that of the twenty 
species which are known to inhabit the shores of the North American continent we found twelve, 
or more than half, upon a little reef at Dix Point, a few rods to the eastward of our laboratory at 
New Providence, in the Bahama Islands. 

Of the thirteen species which wo found in the islands several are new, and as none of them 
have ever been adequately described, an illustrated, systematic description of all the species is 
now in preparation by Mr. Herrick. The present memoir deals only with the embryology and 
metamorphosis of the genus. This is a new field, for nothing whatever has as yet been ]»ublis"!ied 
upon the embryology of any species of the genus, and all our knowledge of the metamorphosis is 
contained in two short abstracts without illustrations on the metamorphosis of a single species, 
Alpheus lieterochelis. Rggs have now been obtained from all thirteen of the Bahama species, and 
the first larval stages of most of them have been reared from the eggs in acpiaria in the laboratory, 
and the metamorphosis has been traced from actual moults. 

THE HmTAMORPHOSIS OF ALPHEUS. 

One of the moat remarkable results of our sttuly of the varijus species of the genus Alpheus 
is the discovery that, while there is such a general similarity as we might expect between the 
larval stages of the <Iifferent species, the individimls of a single species sometimes differ more from 
each other, as regards their metamorphosis, than the individuals of two very distinct species. 
This phenomenon has been observed by us and carefully studied in two species — Alpheus lietero- 
chelis and Alpheus suulcyi—nud it is described in detail, with ample illustrations, in the chapter on 
the metamorphosis of Alpheus. In the case of the first species the difference seems to be geo- 
graphical, for while all the individu.als which live in the same locality pass through the same series 



330 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

of larval stages, the life history of those which are found at Key West is very diifereut from that 
of those whi^h live on the coast of North Carolina, while those which we studied in the Bahama 
Islands present still another life liistory. In the case of the second species — Alpheus saulcyi — the 
difference stands in direct relation to the conditions of life. The individuals of this species inhabit 
the tubes and chambers of two species of sponges which are often found growing on the same 
reef, and the metamorphosis of those which live in one of these sponges is sometimes different 
from thai of those which inhabit the other. In this species the adults also are different from 
each other, but as we found a perfect series of transitional forms there is no good reason for 
regarding them as specifically distinct, and in the case of the other species — Alpheus heterochelis — 
we were unable, after the most thorough and minute comparison, to find any difference whatever 
between a<lnlts from North Carolina and those from the Bahama Islaud.s, although their life histories 
exhibit a most surprising lack of agreement. In fact, the early stages in the life of Alpheus hete- 
rochelis in the Bahama Islands differ much less from those o{ Alpheus minor or Alpheus normani 
than tliey do from those of the North Carolina Alpheus heterochelis, and, according to Packard, the 
Key West heterochelis presents still another life history. 

In the summer of 1881 1 received the American Naturalist with Packard's very brief abstract 
of bis observations at Key West upon the development of Alpheus heterochelis, and read with great 
surprise his statement that this species has no metamorphosis, since, while still inside the egg, it 
has all the essential characteristics of the adult. As I bad under my microscope at Beaufort on 
the very day when I read his account a newly hatclied larva of the same species and was engaged 
in making drawings to illustrate the metamorphosis of which he denies the existence, and as my 
experience in the study of other Crustacea had taught me that all the larvae of a species at the 
same age are apparently facsimiles of each other down to the smallest hair, Packard's account 
seemed absolutely incredible, and I hastily decided that, inasmuch as it was without illustra- 
tions and was written from notes made many years before, it involved some serious error and was 
unworthy of acceptance. This hasty verdict I now believe to have been unjust, since my wider 
acquaintance with the genus has brought to my notice other instances of equally great diversity 
between the larv;t of different specimens of a single species. 

The phenomenon is, however, a highly remarkable one and worthy the most thorough exami- 
nation, for it is a most surprising departure from one of the established laws of embryology — the 
law that the embryonic and larval stages of animals best exhibit their fundamental afiBnities and 
general resemblances, while their speqific characteristics and individual peculiarities make their 
appearance later. 

As in most animals the adult life is most important, the adults have a more diversified envi- 
' ronment than the young, and the divergent modification which is continually taking place to 
perfect the adjustment between such organism and its conditions of life chiefly affects the adults, 
so that specific characters and the slight differences between varieties or races are usually con- 
fined to the adults, while the embryos and larvse are, as a rule, more generalized. 

This is true to a marked degree of those animals whose young are nursed or protected or cared 
for in any way by their parents, and while it is less true of those animals whose independent life 
begins very early, yet the same law holds with them also ; and the chief scientific value of embry- 
ology lies in the fact that a knowledge of the early stages in the life of animals enables us to trace 
their broad affinities and to distinguish them from more recently acquired differences; for the 
early stages of two related forms of life share in common their more fundamental characteristics 
and are essentially alike, while the adults differ from each other and exhibit the divergent speciali- 
zations which are of more recent acquisition. 

It sometimes happens, however, that the early stages of two closely related species differ 
greatly. This may occur when the larvae of the one species lead a free, independent life, while the 
young of the other species are protected in some way by the parent. For example, the compli- 
cated metamorphosis which is so characteristic of starfishes is almost totally absent in those star- 
fishes which are provided with brood-pouches. The same relation may also bo exhibited when the 
larvae of one species of a genus have become adapted to a mode of life very different from that of 
the larvai of the other species of the genus. Thus those species of ^ginidae whose larvae are para- 



MKMOIRS OF THE >'ATIOXAL ACADEMY OF SCIENCES. 331 

sitic multiply aaexually duriug the larval life and build up complex communities, while nothing of 
the sort occurs in tiiosc species with free larvie. 

Many similar cases might be given, but we must bear in mind that they are all very dillerent 
from the one now under examination. In alt such cases the difference is between the larva; of two 
distinct species, while in Alpheus we have a similar difference between the larvio of individuals of 
a single species. 

Among other animals it is not very unusual for certain individuals which are placed under 
conditions exceptionally favorable for embryonic development to be born in a more adviuiced stage 
than the normal for the species, and in such cases the larval metamorphosis is abbreviated by the 
omission of the earlier stages. 

This abridgment of tlie larval life is not common, but many cases are known, and if the his- 
tory of Alpheus were simply another illustration of this process of abbreviation it would not be at 
all anomalous, although the existence of three well marked and fixed grades of abridgment in 
Alpheux heterochelis, in three widely-separated localities, would still be remarkable and interesting. 
I The life I'.istory of the North Carolina form of this species is more abbreviated than that of 
the Baliama form, and the metamorphosis of the Key West form is still more shortene<l, but, in 
addition to the abridgment, the different forms also present most important differences in structure 
and in the order in which the appendages are developed; diiferences which are much more funda- 
mental and profound than the mere length of the larval life. 

The varioius larval forms are described with so much detail in the chapter on the metamor- 
pho.sis of Alpheus that it is not necessary to repeat them here, but the following very brief outline 
will serve to call attention to a few of the most conspicuous features: 

As several distinct species of the genus Alpheus pass through a long metamorphosis, each 
stage of which is almost exactly the same in all the species, we may safely assume thgj; this is the 
primitive or ancestral metamorphosis which was originally common to all the species. It has been 
traced in AJ2)heus minor by me at Beaufort, North Carolina, and by llr. Herrick in a similar species 
at New Providence. Mr. Herrick has also traced it at New Providence for Alpheus normani and 
Alpheus heterochelin. In all these forms the larva hatches from the egg in a form which is very 
similar to Fig. 2 of PI. xvi, and very shortly after hatching it* moults and passes into the second 
larval stage, which is the one /rom which Fig. 2 was drawn. This larva has all its appendages 
fully developed and functional as far backwards as the third pair of maxillipeds. Following these 
are three bud like rudiments, to rei)resent the first, second, and tifili thoracic limbs, and posterior 
to these a long, tapering, imperfectly-segmented abdomen, ending in a flat triangular telson. 

The locomotor organs are the plumose antennae and the exojwdites of the three pairs of max- 
illipeds. 

After the second moult the larva passes into the third stage, wliich is shown in PI. xvi. Fig. 1, 
and PI. XVir, Fig. 1. The first and fifth thoracic limbs are. now futictional ; all the abdominal 
somites are distinct and movable, and the urojiod, or sixth abdominal appendage, has api)eared, 
and its exopedite is functional and fringed with plumose hairs, while its endopodite is rudimentary. 
The five abdominal appendages have not yet ajipeared. 

The fir^t thoracic leg, whi<;h was represented by a bud in the preceding stages, has now 
acquired a Hat, basal joint and a swimming exopodite like those of the maxillipeds, but its endo- 
podite is rudimentary. 

The fifih thoracic limb is fully developed and is the most conspicuous peculiarity of the larva 
at this stage of development. It has no exoj)odite; its basal joint is not enlarged nor tlattened, 
and its long, (cylindrical, slender shaft is i)rolonge(l at its tip into a long lancc-Iike Iiair, which 
projects beyond the tips of the antenna'. 

After its tliiid moult the larva passes into the fourth stage, whidi is shown in 1*1. xviii, Fig. 3. 

The carapace now begins to extend over the ej'es, and the ears make their appearance in the 
basal joints of the antennules. There are now five pairs of plumose locomotor exopodites, belong- 
ing to the first, second, and third maxillipeds, and the first aiid second tlioractic limbs. r>etween 
the latter and the el<)ngate<l fifth thoracic limb are buds to represent the third and fourth. The 
telson has become narrow and elongated, and the uropods are fully developed, although there is 
as yet no trace of the other abdominal appendages. 



332 MEMOIRS OF THE NATIONAL ACADEMl"* OP SCIENCES. 

After the fourth moult the larva passes into the fifth larval stage, when it resembles Fig. 1 of 
PI. xxr, so far as concerns the anterior end of the body, from which it differs greatly as regards 
the telsou and uropods. The eyes are now well covered by the carapace, and the swimming 
organs are the seven pairs "of exopodites belonging to the three maxillipeds, and the first four 
thoracic limbs. The first five pairs of abdominal appendages are now represented by buds, like 
those shown in PI. xxi. Fig. 1, but the telson and uropods are nearly like those of Fig. 3, in PI. 
XX. The telson is narrow and much elongated, and its marginal spines are very small. 

During the moults which follow, the abdominal appendages become fully developed, the eyes 
become completely covered by the carapace, the autennule develops a scale, the antenna elon- 
gate, the swimming appendages of the midbody disappear, these appendages assume their adult 
form, and the animal gradually becomes like the young Alpheus shown in PI. xx. Fig. 2. 

This life-history is common to Alpheus minor at Beaufort and New Providence and Alpheus 
normani and Alphe^is heterochelis at New- Providence, although the latter species presents a totally 
diftereut life-history at Beaufort. Before it hatches, this form, as shown in PI. xx, Fig. 1, reaches 
a ilegree of development which bears a general resemblance to stages two and three of the Bahama 
form, with certain differences which are pointed out in the sequel. 

Immediately after hatching it assumes the form which is shown in PI. xix. Fig. 2, and Fig. 1. 
The animal has now all the somites and appendages of the adult, but all behind the maxillipeds 
are rudimentary, and there is little power of locomotion. The first moult occurs in a few hours, 
and the larva assumes the form shown in PI. xx. Fig. 3, when it is no longer a larva but a young 
Alpheus. The eyes are almost completely covered by the carapace, the ear is well developed, the 
tiagellum of the antenna has elongated, and the other appendages have assumed the adult form. 
An older specimen is shown in PI. xx, Fig. 2, and a still older one in PI. xvii. Fig. 3. Careful com- 
parison will show that no exact parallel can be drawn between any larval stage of this form and a 
stage of the first form, and that we have to do with something more profound than simple accele- 
ration of development. The Bahama heterochelis has, at first, three, then four, then five, and then 
seven fully developed and functional exopodites, while the North Carolina form never has more 
than three. As regards the thoracic region and the first five abdominal appendages the Beaufort 
larva, at the time of hatching, is more advanced than the fourth larval stage of the Bahama form, 
while the uropods are like those of the Bahama form at the time of hatching. 

In the latter the first and fifth thoracic limbs are the oldest, arud the others appear in succes- 
sion, while all five pairs appear together in the Beaufort form. In the Bahama form the uropods 
appear before and in the Beaufort form after the others, and many minor differences show that we 
have to do with profound modification of the life history rather than with simple acceleration. 

Packard's short account of the development of those specimens of this species which occur 
at Key West shows that these differ from the Beaufort specimens about as these latter differ from 
the Bahama specimens. 

The second species is probably A. saulcyi, although Gu6rin's figure and descri])tion of this 
form are not in accord with it in some important points. It is found in the Bahama Islands, living 
in the tubes and chambers of two species of sponge, a green one and a brown one. Those found 
in the green sponges have many small eggs, while those fonnd in the brown sponges have only a 
few large eggs. The eggs from the green sponge hatch in the stage shown in PI. xxi. Fig. 1. It 
has rudimentary gills, the eyes are imperfectly covered, the antennules and antennas are beginning 
to assume their adult form, and the exopodites of the three pairs of maxillipeds are tlfls chief organs 
of locomotion, although all the appendages are represented. The abdominal feet are rudimentary, 
however, and the uropods are covered by the cuticle of the telson. 

Very soon after hatching the larva moults and assumes the form shown in PI. xxi. Fig. 2. The 
eyes are more completely covered, the antennules and aiitenniB are elongated, the thoracic limbs 
have the adult form and the pleopods are all functional. 

In twenty-five or thirty hours after hatching it moults for the second time and passes into 
the third stage, which is shown in Fig. 8. It is no longer a larva, but a young Alpheus, with all 
the structural characteristics and pugnacious instincts of the adult. 

In a few cases the development of this species is still uiore accelerated, and a few eggs from 
animals taken from the brown sponge hatched in the stage shown in Fig. 8, instead of the stage 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



3B8 



shown in Fig. 1. The following notes on the variations in the coloration and habits in Alplieus, 
particularly in .4. saulcyi, are taken from a paper by Mr. Ilerrick published in the Johns Hopkins 
University circulars. 

VARIATIONS IN THE HABITS AND COLORATION OF ALPHETJS. 



Some of the species of Alpheus are usually or even universally found living as parasites within 
the water tubes of sponges, and it is extremely interesting to find that individuals of the same 
species, living in ditferent species of sponges, may themselves ditier greatly in color and in habits. 

A large brown sponge, Hircinia arcuta, which is not to be mistaken, grows on the shallow 
reefs and off the shores of many if not all the Bahama Islands. This is called the " loggerhead 
sponge" by the fishermen, and is found from just below low-tide mark out to one-half a fathom 
or more of water, where its great size and sooty brown color distinguish it at onco on the 
white bottom. If a sponge colony of this kind be pulled and torn apart, one is certain to find it 
swarming with a small species of Alpheits, which quarter themselves in the intricately winding 
pores of the sponge. Hundreds, or even thousands of individuals might be collected from a single 
large specimen. These animals vary from one-eighth to three-fourths of an inch in l«iigth. They are 
nearly colorless, excepting the large chehe, which are tipped with brown, reddish orange, or bright 
blue. The females are so swollen with their eggs or burdened with the weight of those attached 
to the abdomen* that they can crawl only with great difficulty if taken from the water. The eggs 
are few in number and of unusually large size, their diameter varying from one twenty -second to 
one twenty-fifth of an inch, and their number from six to twenty. These are most commonly yellow, 
but may be either bright green, olive, flesh color, brown, or dull white. 

Another quite different sponge grows on all the reefs in from one to two fathoms or more of 
water. There are several varieties of this, which may be told by their olive-green color, yellow 
flesh, and clumpy, irregular shape, as well as by the putrescent mucus which some of them pour 
out when broken oj)en. In nearly nine out of ten of these sponges one will find a single pair of 
Alphei which resemble those living in the brown sponge in most particulars, although they differ from 
them in several important points. They are distinguished by their large size, and by their peculiar 
and very uniform color. They vary in length from two-thirds to one and two-thirds inches. The 
females exceed the males greatly in bulk owing to the great size and number of their eggs. 

Both sexes are nearly transparent and colorless excepting the large claws, which are bright 
vermilion-orange ( PI. iv). The female is practically inert during the breeding season (which lasted 
during our stay, March to July), and at such times is well protected in her sponge, or against any 
green surface, by the bright green ovaries which fill the whole upper part of the body, and by the 
mass of similary colored eggs attached to the abdomen below. Only two pairs, or four individuals, 
out of a hundred or more which were examided showed any variation from these colors. In these 
the eggs were yellow, and the pigment on the claws more orange than red. The table which fol- 
lows shows the variations between two large females taken respectively from the brown and green 
sponges, and between the size, number, and color of the eggs. 



Habitat of Alphdiis. 


Leogtb of 9 


Number of 
eggs. 


Diameter. 


Color. 


Color of adolt. 


Brown sponge 

Green Bponge 


Tnehe*. 
i 


11) 
347 


Inches. 


Yellow (variable). 

Usually green ; in this 
case yellow. 


Large chelas, red, bine, 

or brown. 
Largo cliehp, always 

orange-red. 



These two forms, apparently distinct, are seen however, by closer examination, to belong 
to the same species, although they show very interesting variations. The Alpheus living in the 
brown sponges tends to vary in several ways, chiefly in size and in the color of the body and eggs. 
The rostrum usually has three spines, but occasionally only two are present, the median one being 
lost. It is evident that these animals are perfectly protected from outside enemies while within 
the torfuous mases of the sponge, as their numbers would show. Parasites such as Isopods, how- 



334 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

ever, are not uucoinmou. There has thus been uo chance or ueed for natural selection to act along 
the line of color. On the other baud, possibly, the Alpheus of the green sponge does retjuire color 
protection, since the females are very sluggish during the breeding season, which extends over a 
o-ood ijart of the year. This animal is certainly well protected against any green surface, as already 
stated. But as will be shown, natural selection has probably nothing to do with it. The bright col- 
oring of the tips of the claws, which only are protruded from the place of concealment, recall the 
similarly colored beads of boring annelids which abound ou the reef, and may have a protective 
significance. This evidence, however, is not very reliable. 

The colors of certain Crustacea, and also the color of their eggs, are known to vary greatly 
with the surroundings. In the Alpheus parasites in the brown sponges these colors vary consid- 
erably where the surrounding conditions are the same. However, the color of the ovarian eggs is 
always the same as that of those already laid, and although these animals were kept for several days 
at a time in diflereutly colored dishes, we never observed any very marked change in the color of the 
eggs, but these ex[)eriments were not continued long enough or carefully enough to be conclusive. 
The eggs of Alpheus hecterochelis are almost invariably of a dull olive color, while as in the case of 
the parasite of the green sponge, about one in a hundred has bright yellow eggs. In the first case 
at least this is possibly an instance of reversion to one of the original colors from which the green 
was derived by natural selection. In most species of Alpheus the color of the eggs is fixed and 
uniform, and as already suggested may have a protective significance, but in a few other cases 
where this is not true, the color is not only variable in difterent individuals, but probably also in 
the same individual. 

In order to explain the variations which we find in these two forms, we must assume either (1) 
that the parasites of the green sponge are a fixed variety with distinct habits, or (2) that they repre- 
sent individuals which have migrated from the brown sponges and adapted themselves to their 
new surroundings, or further (3) that only those chance individuals with orange-red claws .and 
bright-green eggs, which occasionally occur in the brown sponge, find their way to the smaller 
green species, where they acquire great vigor and size. This last supposition is evidently untena- 
ble. If moreover the two forms, which were at first supposed to be specifically distinct, re])resent 
fixed varieties, we ought to find the young or at least adults of all sizes in both sponges, whereas it is 
only in the large brown variety that any small or undersized individuals occur, while a single pair, of 
large and tolerably uniform size, is invariably found in the exhalent chambers of the green sponges. 

These and other considerations render it probable that the second (2) proposition above stated 
is the correct one, viz, that the parasites of the green sponges were born in the brown variety, and 
after attaining considerable size migrated thither, where they adapted themselves at once to their 
slightly ditterent surroundings, growing to thi-ee or four times their former size, and the females 
acquiring bright green eggs, which become a source of pi^otectiou in their new habitat. This view 
implies the greatest variability in color and in size of the individual, and in the color of the egg, 
which is more remarkable from the fact that it is quite unusual in this genus. 

THE EMBRYOLOGY OF ALPHEUS. 

At my suggestion Mr. Herrick undertook, in 1886, the study of the embryology of Alpheus, 
and devoted a considerable part of bis time for three years to this subject, and while he carried on 
the work under my general supervision the results which be has reached are entirely bis own, and 
my share in the chapter which is devoted to this division of the subject is only that of an instructor. 
I must call attention, however, to the fact that Mr. Merrick's studies were begun at a time when 
our knowledge of the embryology of the higher Crustacea was far less complete than it is at the 
present time. From time to time brief abstracts of tbe progress of the research have been written 
by Mr. Herrick and published in the Johns Hopkins University circulars, and the following cor- 
rected summary of his results contains the substance of these preliminary reports. 

The work was begun at Beaufort, North Carolina, and the eggs of the two species of Alpheus 
which occur there were carefully examined and preserved for laboratory research, but much better 
and simpler material was afterwards obtained at the Bahama Islands, the early stages were much 
more thoroughly studied, and the development of the animals was traced in detail, step by step, 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 335 

from the first nucleus of the fertilized egg, through all the einbryouic and larval stages, up to the 
adult condition. The eggs of each of the thirteen species whicih occur in the Bahamas were ob- 
tained and studied sufficiently to ascertain what are the si)ecific dittorences in development, and 
four species were studied exhaustively, in detiil. These four are Alpheus heterochelin, Say ; A. wit- 
«M«, Say; A. saulcyi, nwd the Bahama Ac<eroc7tt'/(.s-. Uidess otherwise stated the following note.s 
on the early stages refer to the hist species. The development in the egg is the same for all, except- 
ing A. minor, which will be referred to separately. 

This prawn has proved to bo a good subject in which to study the origin and role of certain 
much disputed bodies, which are met with in several Crustacea, the "secondary mesoderm cells." 

SEGMENTATION OK TUE NUCLEUS AND OF THE YOLK. 

The egg when laid, is enveloped by a single membrane, the chorion or shell, to which is added 
the secondary membrane of attachment. If ihe nucleus is unfertilized, it is not able to initiate the 
process of segmentation. The fertile nucleus divides, and its products pass towards the surface, 
until a syncytium of eight nuclei is formed. Either just before or after the division of these, 
the yolk undergoes segmentation simultaneously over the whole surface into a similar number of 
partial pyramids. Each yolk pyramid has a large nucleus at its base, while its apex fuses with 
the common yolk mass in the interior of the egg. The process is now a regular one until 128 to 25(j 
small segments are formed. The rate of cell multiplication is then retarded over one half of the 
egg, while it still continues and perhaps is accelerated over the remaining portion of it. The egg 
thus loses its radial symmetry and becomes two-sided. It is important to notice that no products 
of the segmentation nucleus are left in the interior of the yolk. The superficial i)yramidal 
structure is lost; the primitive blastoderm is established, and there now takes place a general 
migration of nuclei from flie surface to the yolk within, but principally, as would be exjjccted, 
from that part of the egg where the blastoderm cells are most numerous, corresponding to the 
future embryo. This is followed by a partial secondary segmentation of the food yolk info balls. 
The yolk-ball is apparently fprmed about the migrating nucleus, bat as the latter is moving, this 
segmentation is irregular. 

Mr. Herrick has been able to follow very closely the entire process of segmentation in Stenopus, 
where it is substantially the same as that just described, except that there is no general migration of 
cells from the surface, prior to invagination. This is also true of Poutonia domestica, and it is quite 
probable that the majority of niacroura pass through the same phases in their early development. 

Alpheus minor is anomalous from the fact that the products of the first nucleus instead of 
multiplying by regular binary division, multiply indirectly, and give rise to numerous nuclei, 
many of which degenerate, before the blastoderm is formed. 

THE INVAGINATION STAGE. 

A slight invagination occurs where the superficial cells are thickest, and the egg becomes 
what has been generally regarded as a modified gastrula. The depression is shallow, and does 
not form an inclosed chamber within the yolk. The included cells multiply rapidly, and form a 
mass of nearly similar elements, some of which pass into the yolk. The protoplasm surrounding the 
nuclei of these cells is |)rolonged into a reticulum, which encloses myriads of small yolk frag- 
ments, and probably digests them by an intracellular process, after the manner of feeding amiebie. 
The thickening in front of and surrounding the pit, which is now obscured, is the rudiment of the 
abdomen. Anteriorly the " procephalic lobes" or more properly the optic disks make theirappear- 
ance on either side of the long axis of the embryo, as circular patches of ectoderm. Meantime 
nuclei wander from the cell mass below tlie abdominal plate to all parts of the egg. Some pass to 
the opposite side, and take np a position beside the flattened epithelial cells, of what was the i»rlm- 
itive blastoderm. The majority, however, pass forward and u[)ward in divergent lines from the 
sides of the abdominal plate, and eventually large numbers of these wandering cells settle down 
over the dorsal surface of the embrj'o. 



336 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 



PRODnCTS OF CELL DEGENERATION. 



At the beginning of the egg-nauplias period, when numerous wandering cells have passed 
forward and joined the inner surface of the embryonic ectoderm, certain new bodies begin to appear 
in great numbers. They vary in size from small refringent particles to bodies nearly as large 
as ordinary nuclei. The latter stain deeply and nearly unitbrmly, but with high powers it is 
often possible to demonstrate a clearer zone about them, which might be mistaken for a layer of 
cell protoplasm. How do these bodies, the so called " secondary mesoderm cells," originate and 
what is their function? As to their origin there can be no doubt whatever. They arise by a 
process of degeneration from the embryonic cells or nuclei, chiefly from those wandering cells just 
described. Many of the latter may be seen to be swollen out and their chromatin divided into 
coarse grains and balls of various sizes. The wall of the cell breaks down and thus sets the chro- 
matin granules free, or, more correctly, the products of the degenerating chromatin. 

These degenerating bodies are most marked in the fully developed egg-nauplius, where there 
is a large accumulation of them around the oesophagus and at the bases of the rudimentary 
appendages. After this stage they generally disappear from these regions. Somewhat later, 
however, when there is a well developed nervous system and six pairs of post-naupliar appen- 
dages, a patch of ectoderm cells on the surface of the egg opposite the embryo proper becomes 
noticeable. It reminds one of a median unpaired "dorsal organ." A slight invagination appar- 
ently takes place at this point, but at any rate a number of cells pass into the surrounding yolk, 
and these give rise in the way described, to a swarm of minute particles of chromatin products. 

Before any pigment is deposited in the eyes, it is easy to demonstrate the presence of blood 
corpuscles in the stream of plasma which bathes the nervous system. They have the adult 
characteristics, that is, they possess a deeply staining nucleus and a clear irregular body. In the 
nauplius Stage, moreover, some of the larger "secondary mesoderm cells" have a similar appear- 
ance, but there is no evidence that they ever become blood cells. Mr. Herrick's study of these 
bodies has shown that Reichenbach's views on the function of secondary mesoderm cells of Astacus 
are probably erroneous. According to this naturalist they arise from the nuclei of the endoderm 
cells, forming the ventral wall of the primitive stomach, and are converted into mesoderm. 



THE GERMINAL LAYERS. 



The apparent plasticity of the embryonic cells and layers and the comparative tardiness with 
which they are clearly differentiated can not fail to impress anyone who follows closely the early 
stages of development. The cell mass developed around the invaginate area, forming the thoracic- 
abdominal process, can not be artificially divided into layers. It certainly represents very largely 
the primitive mesoderm, but some of its elements pass to the opposite pole of the egg and become 
almost indistinguishable from the superficial ectoderm, although it will be shown that they do not 
pertain to this layer. A part of this mass remains as the mesoderm of the rudimentary abdomen, 
while many of the cells which migrate from it degenerate and perform a nutritive fiinction. 

The endoderm does not appear as a definite layer until the egg-nauplius stage. It arises from 
wandering cells which assume a peripheral position, and, joining the cells of the hindgut, form the 
walls of the mesenteron. 

THE EYH. 

The optic discs appear as patches of ectoderm, one cell thick on either side of the long axis of 
the embryo in front of the rudimentary abdomen. Before the appendages are definitely formed, 
these have become thickened ectodermic discs. This thickening is due (1) to delaminatiou, or to 
a division of cells in a plane parallel with the surface; (2) to emigration of cells from the surface, 
due to crowding or to a division of superficial cells in a plane at ri.^ht angles to the surface. A disc 
of cells is thus formed which gives rise chiefly to the eye and its ganglia. The cord of cells uniting 
the two optic discs represents mainly the future brain. The eye proper is due to the differentiation 
of the outer layer of the cells of this disc, while the ganglion is developed from the inner layer. 
For fuller results of later studies not represented by these partial and preliminary notes, reference 
must be made to Mr. Herrick's completed paper and to the summary of the whole history of the 
development in the egg given at the end. 



MEMOIRS OF THE NATIONAL ACADEMY OF SOII^NCES, 337 

GONODACTYLUS CHIKAaRA. 

There are few orders of aiii nulls of which we are more ifjiioraiit than we are of the Stomato- 
podis. They are well known as niiiseiiin specimens, and every natural-history cabinet contains one 
or two, which have been brought home as rare curiosities from <listant seas; but we know hardly 
anything of the habits of the living animals. They are abundant and widely distributed, but like 
most rapacious animals they are very alert, taking alarm at the slightest disturbance and retreat- 
ing to the depths of their burrows at the bottom of the ocean, where they are so completely hidden 
fiom observation that their ca[tture is difficult, and any attempt to study them in their homes is 
almost out of the (luestiou. 

The habits of SciuilUe are tolerably well known, and iu my report on the Stomatopoda, collected 
by II. M. S. Clinllenf/ef, I have given an account of the habits of Lysiosiiuilla based upon observa- 
tions made at Beaufort, North Carolina; but, exce[>t for a few scattere<l and fragmentary notes in 
the various descri[)tive papers, this is the whole of our knowledge of the order. During the sea- 
sons of ISSfJ and 1887 I was so fortunate as to find in the Bahama Islands Oonodactylus chiragra 
living iu localities which were peculiarly favorable for observing its habits, and I am now able to 
supplement mj- report upon the Challenger collections by an account of this interesting species, of 
which little had hitherto been known, except the fact that it is the most cosmopolitan of the 
Macroma abounding on the shores and islands of all tropical and subtroi)ical seas. 

I also obtained its eggs in abundance iind succeeiled in rearing the young from them iu 
aquaria, and am now able to make a contribution to a subject upon which there were hitherto no 
direct observations, for it is a noteworthy fact that while the older larvtB of Stomatoi»oda have 
long been known, and while many genera and species of them were carefully figured and described 
and named by the older naturalists before their relationship to the adult Stomatopoda was sus- 
pected, not a single siiecies in the whole order has, so far as I am aware, been reared from the 
egg and in this way identified witli its specific adult. 

While the adults usually inhabit burrows in the bottom the larvae swim at the surface of the 
ocean, and as noue of the animals which are captured in the surface uet exceed them in beauty 
and grace, their glass-like pelagic larviie are familiar to all naturalists who have had au opi)()r- 
tunity to study the surface fauna of the ocean. Tiieir perfect transi)arency, which permits the 
whole of their complicated structure to be stu<lied iu the living animal, their great size and 
rai)acity, the graceful beauty of their constant and rapiil .novements, can not fail to fascinate the 
naturalist. Unfortunately they are as difficult to study as they are beautiful and interesting, and 
notwithstanding their great abundance and variety, only two or three of them have been traced 
to their adult form. 

Unlike most Malacostraca the Stomatopoda, instead of carrying their developing eggs about 
with them, deposit them in their deep and inaccessible burrows under the water, where they are 
aerated by the currents produced by the abdominal feet of their parents. The eggs quickly 
perish when deprived of this constant current, and as it is very diUicult to obtain them at all, I know 
of no Stomatopod which has ever been reared from an egg under observation. The older larvse 
' are hardy and are easily reared, but they are*eldom found near shore, and microscopic research 
is so difficult at .sea that I know of only two cases in which they have been kept until they assumeil 
the adult form. As I have stated in my rei)ort on the Challenger Stomatopoda, I have reared a 
young Lysiosqnilla excavatrix from an old larva which was captured at the surface, and Faxon 
has in the same way obtained the young Squilla empusa. The .young larviB are common near 
shore, but as they seldom survive a moult in captivity they can not be identified in this way. 

The growth of the larvse is slow and the larval life long, and as they are as independent ami 
as much exposed to changes in their environment and to the struggle for existence as the adults 
they have undergone secondary modifications which have no reference to the life of the adult, and 
are therefore unrepresented in the adult organism. The larvie have been arranged in genera and 
species, but their generic characteristics are quite diflferent from those upOn which the adult genera 
are based, and this is true in a still greater degree of their specific chara(;teristics. As thej' 
undergo great changes during their growth different stages have been described as distinct species 
or even genera, and it is not easy to select from the rich gatherings which are brought home by 
S. Mis. 94 22 



338 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

collectors the successive stages in the history of a single species. Like the adults, they are widely 
distributed, and a gap in a series from the North Atlantic may be filled by a specimen from the 
coast of Australia or the Sandwich Islands, and the collection from a single locality may contain 
the larva} of several widely-separated species of adults in all stages of growth as well as the larvje 
of deep-water species which are as yet entirely unknown. 

The attempt to unravel the tangled thread of the larval history of the Stomatopods is there- 
fore attended with very exceptional difficulties, and the earlier writers were content to rest after 
the bestowal of generic and specitic names upon the larvip,. As I found after the Challenger collec- 
tion was placed in my hands that it was very rich in larvte, I attempted to determine, by compari- 
son, the larval series for each genus, and the methods which I employed for making the comparison 
are fully stated in my report. As one of the results of this comparison I ventured to describe the 
general characteristics of the larva of the genus Gonodactylus (p. 113), and in PI. xii. Fig. 5, of 
that report I figured a larva which I ventured to call the larva of Gonodactylus. A comparison of 
that figure with PI. xv. Fig. 11 of this memoir will show that this determination was correct, for 
the larva of Qonodactylus chiragra which is here described is so much like the one figured in the 
Challenger report that they belong, in all probability, to the same species. 



CHAPTER II. 
THE LIFE HISTORY OF STENOPUS, 



By Francis H. Herkick. 



This paper is the result of observatious made at Beaufort, North Caroliua, in 1881 aud 1883, 
aud at Nassau, New Providence, in 1887. The niaiine laboratory of the Johns lIoi)kins University 
was stationed at the latter point iu the Bahama Islands from March until July of that year, and 
with the means thus geuerously afforded, I was able to considerably extend my studies upon the 
Crustacea of these coral islands. 

Professor Brooks found a number of peculiar pelagic larvse at Beaufort, and it is very probable 
that they represent a part of the life history of StenopiLs hispidu.s. Plates ix and x, illustrating 
two important st_ages of tliese very interesting larvae, are contributed by Professor Brooks, and 
the descriptions of these stages are based entirely upon his observations 

While the material gatliered in a sojourn of a few months at the seashore is in many in.stances 
incomplete, it seems worth while to bring out this sketch of the Stenopns, inasmuch as nothing 
was previously known of its development, and indeed but very little concerning the adult form. 
IStenojjuii liispidus is, in fact, generally known to naturalists as occurring only in the Indian and 
South Pacific oceans. It was at first quoted from the Atlantic (Cuba) by Von Martens (7) in l.S7i!, 
and it has not since been reported from the Western Continent, so far as we are aware, until we 
rediscovered it at Abaco, Bahama, in 188(1, but any assiduous collector on West Indian coral reefs 
must somewhere have hit ui»on it (v. A[)pendix i). 

As the eggs are quite small, as is the case in all Crustacea with a protozoa stage, they are not 
particularly well suited for study by means of .sections, and no special attempt has been made to 
trace out the history of the germinal layers, a subject which can be dealt with to better advantage 
in other species. The Stenopi breed readily in aquaria, and several series of eggs, illustrating 
fully the segmentation, and some early phases of development were prepared, and the sections 
were afterwards made iu Baltimore. These are given on PI. VI. They are especially interesting, 
since the segmentation is like that of Peuicus studied by Haeckel, who relied wholly uj)ou surface 
observations. 

The ova were immersed in Kleinenberg's picrosulphuric acid and afterwards hardened in 
alcohol. This answered sutlicieutly well for the purpose in hand, although it rendered the eggs 
more resistant than is desirable. 

I. — Tnii NA'4'UEAL HISTORY OF STENOPUS. 

The Bahaman Steuopus (PI. V) measures from IJ to 1^ inches in length. All the appendages 
are long and genorallj' quite slender and delicate, especially the antenna', which give to this iVnin 
a very characteristic appearance in the sea. These are snow-white. They are carried widespread 
and arch outwards in graceful curves. The tlagella of the second or outer antenna! are two and a 
half times the length of the body. In the act of swimming these are bent backward and outward, 
while the outer division of the first or inner anteuuie is carried upward, and their inner branch is 
diuected forward. 

The body is pure white or nearly so, excepting three broad transverse bands of reddish scarlet. 
The first or most anterior of these color bands covers the front of the animal, involving the eyes 
and bases of the antenuie, and in some cases it extends behind the rostrum as far as the mandib- 

331) 



340 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

■ 

ular or " cervical " groove. The second is nearly confined to the broad tergal surface of the third 
abdominal segment, ^hile the third zone crosses the last abdominal somite and impinges on the 
tail fin. The appendages are all colorless excepting the third pair of legs which carry the large 
pincers. These are similarly marked with four bands of the same bright color. As shown by the 
colored plate two of them encircle the great claws, a third belongs to the carpus, and the fourth 
to the meros or fourth segment of the limb. The bases of the third and sometimes of the foUx,.h 
and fifth thoracic legs are tinged with bright blue. The ovaries often give to the dorsal surface 
of the females a light-greenish cast. 

There is but little variation in the size and character of these markings in the same sex or in 
difl'erent sexes, but it is most remarkable to observe how constant these colors are in individuals 
of the species from different parts of the world. We possess two colored drawings of this spe- 
cies* (which will be referred to again), one by Adams (5), from a living specimen taken in 
the China Sea, and the drawing of Dana (6), who found the species on the coral reef of Earaka, 
one of the Paumotu Islands, and at Balabac Passage, north of Borneo. Both of these, and especially 
the Sameraug plate, essentially agree with our Bahaman specimens, which in color seems to be 
the more faithful copj' of nature. Here the basal joints of the thoracic legs are colored blue as iu 
the Nassau form. Why should Stenopus, coming from different seas, retain the same colors and 
markings, to a nicety of shade and pattern, while a cosmopolite like Gonodactylus chiragra (a Stoma- 
topod) presents such wide color variations as to be as unlike as possible, so that scarcely any two 
taken from the same place have a similar color pattern ? To this question we can not at present 
give a satisfactory answer. 

Alcohol soon removes all trace of color from the body, but the spots on the legs remain for a 
longer time as light orange red. Both sexes are of nearly the same size, and, as already stated, 
alike in color. 

Being thus brilliantly decorated with the Amexican colors, our crustacean soon acquired with 
us the name of the " Bandanna Prawn." As we see this animal swimming deliberately in the 
water w e are reminded of some strange and fantastically colored insect. It is by far tlie most 
showy, and for its size the most attractive, member of that giant tamily, the Crustacea, which 
have their dwelling on the reef. One day, when out upon a wading atid diving expedition, a pair 
of these prawns was discovered by turning over a plate of loose coral, and was easily captured by 
slowly raising the slab from the water into the boat ; for this species, unlike some shrimps, is quite 
helpless when once out of its element. More frequently, however, tliey led us to a long chase. 

There seems to be considerable attachment between the sexes, since they are invariably found 
in pairs, the male and female swimming side by side. On a still day they may be found clinging 
to the mosaic of sponges and living coral, which form the reef bottom, but if disturbed they sud- 
denly become very active, and, darting backward by sudden jerks, dive iuto some chink, out of 
reach of the hand net. 

Several females both hatched -and laid eggs in aquaria in the month of June, but the breeding 
season, as inferred from the capture of locomotor larvje, probably extends throughout the spring 
and summer months, if not throughout the entire year. 

The eggs are very numerous. They are nearly spherical and measure one-fiftieth of an inch 
in diameter. They were always of the same light opalescent- green color. The ova are laid at 
night, but the process was not observed. 

Three different females hatched their broods on the afternoons of June 4, 14, and 24, respec- 
tively, and moulted and laid eggs during the following nights. As these animals invariably moult 
just before laying their eggs, the latter are probably fertilized at the time they are laid. The 
hatching of one brood lasted about 9 hours, from 2 o'clock in the afternoon until well into the fol- 
lowing night. By 10 o'clock the same evening some of the larvie had moulted for the first time. 
The eggs are closely felted to the abdomen, and, as in all Decapods, they are cemented together 
by a secretion which possibly comes from the oviducts during ovulation. They are fastened t)y 
the same substance to the hairs which fringe the bases of the pleopods, chiefly to those of the first 
and second ijairs. 

* Besides Milne-Edwards figure (4), evidently made from a specimen iu which the natural colors had been removed 
by alcobol. (See remarks, etc., under Section iv.) 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 341 

After a moult tlie colors are, as is usual, very bright, and tlie moulted skin, as it stands intact 
supported by the antennic, may easily be mistaken for the living animal. These prawns make no 
sounds and appear to be very timid. Tlie surface of the whole anterior body and of the large 
Inlaws is thickly beset with tooth-like spines, the points of which are bent forward, and these 
maj- be regarded as an admirable protection against being swallowed hea<l first by an enemy. It 
is also interesting to notice that the spines of the hinder part of the body project backward, and 
may thus be of service to Stenopus when attacked from the rear. Their long sensitive antenna; or 
"feelers" and well-developed eyes doubtless warn them of aiiproaching enemies, which, by their 
rapid angular movements, they may easily escape. The extraordinary development of the eyes in 
the older larva* (PI. ii) is ren)arkable. 

' The geographical distribution of Htenopxis hispidus is very interesting.* H. Milne-Edwards, 
in his "Eistoire naturelle des Crustacea " (3), gives the habitat of Stenopus hispidus (Latreille) as 
the "Indian Ocean," following Olivier (1) and the older writers. In the " K^gne Animal" of 
Cuvier, third edition, " Les Crustac6s," p. 137, he says : " We know of only one species, rei)orted 
from the Australian seas by Peron and Lesneur." The Samaraug naturalists (5) met with it on 
the coasts of Borneo and at the Philippines in 1843-'4G. Dana, in l.S38-'42, on the Wilkes Expe- 
dition ((3), found it in the South Pacific at the points already noticed. In 1872 E. von Martens (7) 
describes the species for the first time from the Atlantic, in a collection of Cuban Crustacea made 
by Dr. J. Gundlach, and de Man in 1888 (9) quotes it from Amboina in his monograph on the 
Decapoda and Stomatopoda collected in the Indian Archipelago by Dr. J. Brock. 

We can now add to this list the Bahama Islands (Abiico and New Providence). We have 
also the interesting fact that the larva was taken on our coast at Beaufort, N. C, whither it had 
probably been carried by the warm waters of the Gulf Stream. We may th refore exj)ect to find 
the adult Stenopus on the Florida Keys, but not much farther north, since this is essentially a 
tropical form. 

We thus have in Stenopus hispidus anether instance of not only the same genus, but also the 
identical species, occurring on the eastern shores of two continents. It seems not impossible that 
the prolonged larval period which this animal i)ossesses may have played an important [)art in its 
geographical distribution. This may be also true of Gonodactylus chiragra, but on the other hand 
it can not be asserted of Limulus. In the last case the Asiatic and American forms are specificallj' 
distinct. 

n. SEGMENTATION AND EARLY PHASES OF THE EGG. 

The prawn, which hatched her zoea brood on the 4th of June, laid eggs the next morning prob- 
ably at about (5 o'clock, and as soon as discovered some of these ova were hardened at intervals of 
a few hours during the next two days. In this way a complete history of the segmentation was 
obtained. 

First stage. — The first eggs preserved (probably .5 to 6 hours after ovulation) are perfectly 
opaque, nothing but the light-green yolk corj)uscles showing through the shell or egg envelopes. 
Thin sections prove that the segmentation nucleus has divided, and that its two products lie remote 
from each other. Physiologically speaking, we now have two cells, each consisting of a deeply 
staining nucleus and perinuclear protoplasm. The first segmentation is evidently central. What 
takes place is briefly as follows: Primitively we have a central nucleus, about which protoplasm 
is gathered. Around this again is the great mass of yolk, and the whole is encajisuled by the 
protective chorion and the secondary membrane of attachment. The first division involves only 
the nucleus and surrounding protoplasm. The. products as independent bodies now leave their 
central position and seek the surface of the egg. In one instance one of these has reached the 
surface (shown in PI. vi. Fig. 1), while th(> other is only halfway there on the opposite side. The 
superficial cell, as seen by the figure, has the same characters as when buried in the yolk. In 

• The reason for considering the Bahanian form identical with the Hispidus of Olivier, Latreillo, Milno-Edwsrds, 
Adaros, Dana, and others are given on page 351. 



342 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 

another egg of the same phase neither cell is quite at the surface, so that the example ^iven in 
Fig. 1 may be taken to illustrate a tendency, not a rule.* The yolk (Fig. 1, Y. C.) consists here, 
as in subsequent stages, of homogeneous and tolorably unifoim green corpuscles. No vacuolar 
cavities are to be seen. 

Second stage. — Four and one-half hours later the second segmentation is going on or is already 
completed. The egg from which Fig. 2 was taken contains four nuclei with perinuclear protoplasm. 
It was cut into a series of .50 sections, of which the second represented is the twenty-first. Nuclei 
occur in .sections 21, 25, 20, and 35, none being as yet superficial. A portion of section 21 (Fig. 2) 
is shown under a higher power in Pig. 3. 

Third xtaf/e. — After three hours and twenty-five minutes have passed the third phase is reached 
and we have eight cells, around which the yolk is superficially constricted into eight corresponding 
lobes or segments. A surface view of thi.s entire egg and also a section through it are shown in PI. 
VI. Figs. 5 and 6, and a tangential section of one of the nuclei and lobes is given with more detail in 
Fig. 4. The constriction furrows appear to be considerably deeper than they actually are, and we 
might predicate a total segmentation of this egg without the knowledge which the section affords. 
We have here a merely superficial indentation of the yolk, the great central mass of which is undi- 
vided. ' It is a close approach to the yolk pyramid stage seen in Astacus, Alpheus, Hippa, PaliB- 
monetes, and many other Decapods. The dividing^ planes, Figs. 7 and 8 (unless artificially pro- 
duced), do not penetrate into the egg. The furrows extend inward to a plane just below or on a 
level with the nucleus. 

Each nucleus with its outer protoplasm may be spoken of as the cell, and it is hardly probable 
that there is any protoplasm like that surrounding the nucleus in the other parts of the egg. The 
nuclei increase gradually in .size, as seen by comparing the figures of successive stages, and the 
surrounding plasm, which they manufacture out of the yolk, is also of greater bulk. Each is a 
fiattened, oval disc, shown well in transverse section in Fig. 5 at a, and tangeutially in Fig. 4. 
It contains coarse grains and granules of chromatin, and the enveloping protoplasm radiates visibly 
but a short distance between the yolk siiherules. The long axis of each nucleus lies in a plane 
parallel with the surface. Cell multiplication is in all cases indirect, as my observations show to 
be the case with several other related forms, and this is undoubtedly the rule not only with the seg- 
menting eggs of the Decapod Crustacea, but with those of all the Metazoa. There seems to be an 
exception in the case of A Ipheux minor. 

Fourth sttu/e. — After another interval of an hour and five minutes there are sixteen cells re- 
sulting from the fourth segmentation. The blastoiiiercs are less sharply marked at the surface and 
more distinctly polygonal. Six nuclei are cut by the section given in Fig. 7. They are nearer to 
the surface than in the former stage. 

Fifth stage. — The egg represented by Fig. 8 is three hours older than the last and has thirty- 
two cells and the same number of superficial segments. Up to this time the egg has exhibited 
radial symmetry. The nuclei are quite near the surface of the egg. They are more spherical and 
the investing protoplasm is less conspicuous than formerly. The fissures between contiguous 
blastomeres are becoming le.ss and less prominent. 

Sixth stage. — After a longer period, nine hours and forty-five minutes, the process of regular 
division into smaller and smaller superficial .segments has proceeded until 128-256 of these bodies 
are formed. The cells lie at the surface, just under the chorion, and form a continuous envelope, the 
primitive blastoderm about the central yolk. This yolk mass is not segmented, nor does it include 
any nuclei which have not participated in forming the blastoderm. In one or two instances a cell 
was observed just below the service. This may be interpreted as either having never reached the 
surface or as having been there and moved below it towards the interior. But the general state- 
ment is doubtless true that all cells reach the surface, and that there is no extensive migration to 
the interior, as there is in Alpheus, before invagination. 

• It now seems probable to me tb.at tliis superficial cell represents the male .and tbe central cell the female pro- 
nuclens. A small, deeply st.iining body, which I interpret as au undoubted polar cell (not shown in Fig. 1), lies 
underneath the chorion, not far from the superficial cell. 



MEMOIRS OF THE NATIONAL ACADEMY OF SOIENCES. 



343 



Seventh stage. — In three hours iuid three-quarters from the hist phase the bhistoderiiiic cells have 
spread moie rapidly at a piveu point ou the egg, which loses its radial symmetry in consequence. 
There is thus formed the embryonic area or first trace of the embryo proper. 

Eighth or inragi nation stage. — Three and a half hours later a portion of the blastoderm in the em- 
bryonic area is invaginated, that is to say, some of its cells pass below the surface in a bodj', and 
the invagination stage is reached. The invagination is solid, or nearly so, as is the case with 
nearly all Decapods. Fig. 9 represents an oblique section of one end of an egg, through the area 
of invagination, Ig. The epiblastic cells contain small oval nuclei'. There are no yolk cells in the 
interior of the egg. The vitellus is here segmented into large, irregnlas fragments, each of which 
is composed of yolk corpuscles similar to those seen in Fig. 4. It is just i>ossible that this fracture 
of the yolk, which is commonly seen in the eggs of other Crustacea, is artificially produce<l at 
lea.st to some extent, at this stage. 

Ninth stage. — After another period of three and a half hours, while the external change is not 
marked, the invaginated <^ells have rapidly nuiltiplied and given rise to a considerable cell-mass 
below the surface at that point. 

Tenth stage. — In thirteen and a half hours from the last stage, or when the embryo is fifty-two 
hours old, important changes have been etiected. In surface view the embryo presents a heart- 
shaped or somewhat three-sided area. The optic discs appear as widely separated patches of 
ectoderm, united to the thoracic-abdomuial plate, a mass of cells which forms around, but chiefly 
in front of, the point of ingrowth. Sections through this egg show a considerable thickening in the 
optic discs, and an accumulation of large granular cells in the abdominal area. These latter un- 
doubtedly represent some of the primitive mesoderm and endoderm. 

The phenomena just recorded are given iu a more condensed form in the following table, 
which shows the age and corresponding growth of the embryos at the successive stages. The age 
of the first stage is assumed to be 6 hours, which is probably not far from the truth. 

In the above account we are constantly dealing with dift'erent eggs, and assume of course that 
they are all at any given time iu the same phase of development. While this is not strictly true, 
it is very nearly so. The eggs are at first about on a par, and it is only later that some become 
handicapped, producing those slight diflerences which may be seen in embryos from the same 
female.* 

Time of hatcbiDg Jane 4, a.m., early. Tetnperatore SO'^ F. Diameterof egg ^ inch. 



Stage. 

1 
2 
3 
4 

5 
6 

7 
8 


Age or egg. 


State of developmeut. 


6 hrs 


2 cells. 

4 cells. 

8 blastomeres. 

IG blostomeres. 

:t2 Idastomeres. 

ia8-2r)f> blastomeres. 

First trace of embryo. 

Iiivap;ination stage. 

Pit obscured. 

Optic discs and abdominal plate formed. 


llibrs 


14 hrs. 55 min 

16 hrs 


19 hrs 


28 Iirs. 45 miu 

:!2ihr8 


3i>i hrs 


:t8i hrs 


WihT% 





We thus have in Stenopus a typo of the so-called "centrolecythal" segmentation, exactly 
comparable to that of Penams, and essentially like that which is probably characteristic of a 
large number of the Decapod Crustacea. The fact that all the inotoplasm of the egg enters into 
the blastoderm and that no yolk cells are now formed, is of some interest, and this subject, will 
be considered more fully in a paper on the develo[)ment of Alpheus. 



* This is not trne of the American lobster, Homarun americanus, in which I have made a very complete study of 
tlie segmentation process. In a batch of segmenting lobster's eggs, there is a decided Lick of uniformity. Some ova 
which afterwards continue to develop, remain with yolk unsegmented until the third or fourth day after fertilization. 



344 MBMOIEa OP THE NATIONAL ACADEMY OP SCIENCES. 

III. METAMORPHOSIS, OR PERIOD FROM THE TIME OF HATCHING TO THE ADXTLT STATE. 

A. Protoznea or first larva (length =4™"). — Stenopus leaves the egg as a protozoea, which may 
be compared to one of the early larvfe of Penreus or Sergestes, but it is unlike either of them. 
This first larva, which is very long and slender, is so coiled upon Itself in the egg that the tail fin 
overlaps the posterior end of the carapace. It requires considerable time after casting ofif the 
shell to uncoil and straighten its appendages, especially the antenna and the long rostrum which 
was bent under its body. 

The figure on PI. xi exhibits some of the grotesqueness of this larva. This drawing was made 
from an animal which had'just wiggled out of its egg shell and was uncoiling its appendages. 
The huge antenufe are ]>artially unfolded, while the rostrum R., is scarcely visible. Drawings of 
parts of this immature i)rotozoea are seen in PI. vii, Figs. 11-16, and the larva itself as it finally 
ai)pears, about two hours after hatching, in Fig. 11. If we compare with this the younger form in 
Fig. 25, we notice some details, chiefly of a quantitative kind, in which they differ. Immediately 
after leaving the egg the epidermic structures grow rapidly ; hairs or set» are developed on all the 
appendages, and the tail-fin acquires some new characters. The first larva does not swim well 
until several hours after hatching. 

The Stenopus protozoea (PI. ¥ii. Fig. 11) is 4™™ long, the rostrum alone being LJ""". It is color- 
less, excepting the dark eyes and a few scattered blotches of brownish pigment upon the sides of the 
body or on the tail-fin. It swims chiefly by aid of its largely developed autenn?e, whii-h are directed 
forward as shown in the plate. These, with the rostrum, add considerably to the apparent length 
of the body and serve to distinguish it, without the aid of a lens, from the second larva (PI. viii, 
Fig.17), which soon follows and swims about in the aquarium with the others. It is further character- 
ized by the very large size of its mandibles (PI. xi, Fig. 25, Mil.) and by its forked telsou-plate, 
adapted for swimming. The forked locomotor tail-fin and large hairy autenme mark the protozoea 
stage in Crustacea generally. The carapace is only feel)ly developed, not nearly reaching to the bases 
of the appendages. It is prolonged in front into a huge tapering cone, the rostrum, which is nearly 
half the length of the body. This is beset with short spines and reaches considerably beyond the 
antennae. About four segments of the abdomen are distinguishable from before backwards (Fig. 25). 
The first and second, which latter is the largest, carry lateral spines, and the upper surface of the 
second segment is also prolonged posteriorly into a median spine. The tail-fin at the time of hatch- 
ing is sharply forked (Fig. 13) and is furnished with C pairs of rudimentary setie, of which the 
median pair is the shortest, besides a pair of outer non-plumose bristles (Figs. 11, d, and 13, a.). In 
the course of a few hours this organ has become functional and appears as shown in Fig. 11. The 
hairs grow out and acquire thick lateral fringes; the outer pair (next to a) become rudimentary, 
and three additional pairs of toothlike bristles make their appearance on the sides of the telson- 
plate. 

The eyes are sessile. The inner or first antennte (Fig. 25, AI) are jointed, uubranched append- 
ages. Each is tipped with a bunch of about four long sensory filaments and with a single seta. A 
single plumose hair also simngs from the distal end of the i)enultimate joint on its inner side. 
The outer antenniB are biramous. The inner branch consists of a simple stem, tipped with at 
least two long hairs. The outer division is segmented at its extremity, and is garnished with 
plumose setiB, chiefly on the inner margin, there being one or two to each segment. The gland at 
the base of the antennal peduncle is conspicuous. 

The mandibles are of enormous size in comparison with the other appendages. A view of the 
labrum and right mandible is given in PI. vii, Fig. 1.5. They are simi)le blades with rounded 
edges, covered with minute horny teeth. There is no palpus. The first maxilla (Fig. 12) consists 
of two stout branches tipped with bristles, and in the case figured they are spotted with pigment. 
The second maxilla is a broad lobulated plate (Fig. 10). Each lobe is provided with hairs, 
excepting the outermost which corresponds, in part certainly, to the scaphognathite. Only a 
single bristle was detected on This lobe in the specimen from which the drawing was made. 

The three raaxillipeds have each an exopodite, which is considerably larger than the other 
branch, and which is furnished near the tip with not less than three pairs of locomotor hairs. The 
undeveloped condition of these latter in an embryo just hatched but unable to swim, is well shown by 



MEMOIRS OP THE NATIONAL ACADEMY OP S0IBNOB8. 345 

Figs. 14 and 10, which represent the first and third inaxilliped.s of the right side, as seen from 
below. The eudopodites of the second and third pairs possess four joints, of which the terminal 
one carries seta^. There is one jiair of thoracic limbs consisting of a stont locomotive exopodite, 
similar to that of the second and third maxillipeds just desciribed, and of a very short, indistinctly 
segmented endopodite. The latter is armed with two terminal and three lateral plumose hairs on 
tbe inner side. 

H. First zoe'a or second larva (length, a=~)"""). — Five or six hours after hatching the pro- 
tozoea moults into a form which superficially resembles the inacrouran larval type. (PI. Vlll, 
Fig. 17.) The carapace of this larva has grown down so as to cover the basal Joints of all tbe 
appendages, and it also extends behind them. The rostrum is reduced to from one-half to two- 
tbirds its former size, and does not surpass tbe autenual hairs. 

There is still pat one thoracic segment with its appendages. All tbe abdominal segments are 
formed, but none show any traces of limbs. The lateral spines of the first and second somites are 
missing, but the median unpaired spine of tbe latter is greatly developed, and extends to nearly 
tbe end of the third somite. The sixth somite, which carries the zotial tolson, is equal in length to 
the third, fourth, and filth combined. The fjinsbaped telson, viewed from below, is represented 
in Fig. :iO. Comparing this with Fig. 11, we observe that it is no longer conspicuously forked. 
The median notch has a short unpaired spine. There are six pairs of feathered hairs, the outer- 
ones still being rudiments exactly as in tbe first larva, aud a uon-plumose spine which ends the 
series; the three rudimentary spurs seen in Fig. 11 being wanting. The eyes, which have acquired 
short stalks, protrude slightly. 

The autenujB are shorter and are now no longer so important as organs of locomotion. The 
terminal joint of the inner antenna is rediured, but otherwise this appendage is but little changed. 
The outer antenna ends in a stout hook, whi(!h is succeeded, on the indented margin of the inner 
side, by a series of eight feathered hairs. The second joint of this appendage also bears a serrated 
hooked spine at its outer extremity. The mandible is without a i)alp. It has a serrated edge, 
and a prominent, inferior, compound tooth (Fig. 18). 

The inner branch (coxopodite) of the first maxilliB (Fig. 19) carries three simple and three com- 
pound s])ines, while the outer division consists of three segments with stout, plumose hairs, as shown 
in the figure. The second maxilla^ (Fig. 21) are considerably altered from the form shown in Fig. 10. 
There is an outer lobe (scapliognathite), bearing one large hair directed backwards aud at least 
four others which jjoint in the <)|>posite direction. The inner i)ortion is lobulated into six or more 
parts, all of which are well [jrovided with stifl' hairs.* 

Tbe first maxillijjed is shown greatly enlarged in Fig. 22. Examining this in connection with 
Fig. 14, we find that tlie exopodite consists of one segment aud bears a limited number of hairs 
(here twoj at its a])ex. The eiulopodifc^ is segmented and carries numerous hairs, which are 
continued in small tufts along the inner margin to tbe base of the limb. The (rhief swimming 
organs are the first and second maxillii)eds and the first pair of thoracic legs. The inner branch 
of the latter is considerably developed, and nearly equals the exjtodite in length. 

There is a large irregular spot of red jiigment on each side of the anterior half of the body 
just above the base of the third maxilliped. The lobes of the liver (L) begin now to show dis- 
tinctly through the carapace. The food yolk, which is present in small quantities in the stomach 
of the protozoca (Fig. 2'>), is finally absorbed. It was probably owing to this and to the fact that 
I gave the larVa' no food that suited their taste that they never reached the second moult, although 
they i)assed a number of days in this condition. In course of several trials the animals at this 
stage always became greatly crii)pled by i)articles of organi(! matter adhering to theii' body and 
invariably starved. For later stages, therefore, connecting this zoi'-a with tbe adult, we have to 
rely ujwn larvte collected at the surface of the ocean. 

<!. Ml/sis or Scliiznpotl stage. — It is evident that the zoea of the stage B pass(>s into a mysis- 
like form through the intervention of one or more moults, and we have two larvae already noticed 
belonging to the close of this jjcriod. They were collected by at Beaufort, N. C, July 14 and 15, 



* Tbe ditital or termiuul lobe represents tbe endopodite ; tbe lobes next tbis stand for tbe basipodite, while tbe 
second (f) proximal division at tbe base of tbe appendage correspond to the coxopodite. 



346 MEMOIRS OF THE NATIONAL ACA.DEMY OF SCIENCES. 

1883. In the Beaufort specimen (PI. ix) all the segments and appendages of the body are present, 
and all of the latter are functional, excepting the first five pairs of abdominal feet, which are 
rudimentary buds. The carapace is well developed, and termina,tes in front in a slender serrated 
rostum, which is much shorter than in previous stages. The eyes are now large and prominent, 
being mounted on long stalks. These organs, which are sessile in the protozoea, undergo marked 
changes in both size and form in the course of development. They reach a maximum in a later 
stage, and are correspondingly reduced during the passage from the latter to the adult. 

The inner antenna) are biramous ; the outer are reduced to a long narrow scale, armed with 
bristles. The third pair of maxillipeds and first, second, third, and fourth pairs of thoracic legs bear 
prominent swimming exopodites. The fifth pair of pereiopods characterize this larva by their 
great length, and by the huge, paddle-shaped segment, which bears the small, terminal claw. 
There is no exopodite to this appendage. The endopodites of the first, second, and fourth pereio- 
pods are nearly equal ; the third longer. The first five abdominal segments are of equal size . 
and, as stated, carry rudimentary feet. The sixth segment, however, is long and narrow, and has 
the uropods well developed. 

D. Mysis stage. — The larva of stage C moulted into a form (PI. x) resembling the last, with the 
addition of several important features. The inner antenniB consist, as before, of a segmented stem 
with two terminal appendages. The first and third segments of the antennular stalk are short, 
while the second is very long; spine nearly equal to length of basal segment; inner flagellum 
very slender, shorter than the outer branch ; the proximal, thickened portion of which carries 
several (three) bunches of sensory filaments. 

The antennal scale is as long as the antennular peduncle. The flagellum of the antennae now 
appears as a slender filament, nearly twice the length of the scale. Possibly it is formed, as in 
Peniims, from a bud-like remnant of the inner ramus of this appendage in the protozoi?a. The 
third pair of maxillipeds and first to fourth pairs of thoracic legs are as in the jirevious stage, with 
conspicuous exopodites fringed with sette. The endopodite of the fourth pair is longer than that 
of the third ; the fifth pair are twice as long as the fourth ; and the breadth of the penultimate 
segment is much reduced. 

The first, second, and third abdominal segments are equal ; the sixth is narrow, equal to length 
of fourth and fifth. The telson is narrow, tapering, three times as broad at base as at apex; the 
uropods are one-fourth larger than telson. Pigment is found as before, in the extremities of the 
segments of the appendages. Large spots also appear on the abdomen and eyes. 

E. Mastiiioints stage. — On June 15 an older larva than the one just described was obtained in 
the ocean outside the harbor at Nassau. It agrees in the main with the mastigopns of Sergestes. 
The carapace ends anteriorly in a short spine or rostrum, which is bent up at an angle of about 40 
degrees with the body. The eyes are mounted on very long naked peduncles. Both pairs of 
antennai are biramous. The outer flagellum of the first or inner pair of antenna; is the longest (PI. 
XI, Fig. 20), and it bears four or five bunches, containing in all about a dozen sensory filaments. 
The inner branch is a bud. The second antennse extend as far forward as the joint of the first 
pair, where the inner flagellum is given off'. The flagellum of the second pair is wound into a 
short spiral coil. 

The exopodites of the second pair of maxillipeds are rudimentary (PI. xi, Fig. 31). The third 
maxillipeds are now the stoutest appendages, and equal in length the third pair of thoracic limbs. 
The first and second thoracic legs are slender; the third pair is the longest and the* terminal seg- 
ment is bifid; the fourth is a short two-jointed rudiment; the fifth, corresponding to the huge 
oar-like appendage of stage C, is reduced to a bud. It thvs appears that, as in the Sergestids, the 
Jast two jMirs of walldng legs are shed after the mysis period, to be reconstructed again in the masti- 
gopvs stage. 

All the abdominal appendages are functional. (PI. xi, Fig. 27.) The last segment of the abdo- 
men is nearly equal in length to the three preceding. It is laterally compressed, and more nearly 
resembles the adult form. In the act of swimming this larva carries the abdomen bent at nearly 
a right angle to the rest of the body. It is colorless, excejiting areas of red pigment at the bases 
of the abdominal feet, and spots on the lower portions of the antenn.'e ami eye-stalks. There is 
also a transverse band of the same color on the anterior part of the carapace. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 347 

F. ytaHtigopun stage. — After it had been kept three days this larva passed tliroufjh a moult, 
by wliich only slight changes were introduced. The fourth pair of walking legs is now distinctly 
jointed, the lifth remaining as a bud. The flagelluni (endopodite) of the second jiair of anteinnc 
uncoils and speedily Icngtiiens. The terga of the lirst and second abdominal somites bear on the 
lower lateral margins of each side a short tooth. The larva lived four days without further ecdysis. 
Figs. 2(), 27, ;>(), and .''>1 are from this stage. 

G. Maxtiffopus .stage [IM. xi, Figs. 28, 20, .•52-34, PI. Xii|, (Length = it""").— An older larva, 
caugiit in the net on May 7, is shown on PI. xii. The most striking features of this form are the 
long trailing antenna' (flagella of the outer i)air), the actual length of which is about 1 inch, which 
is more, than twice the length of the larva. The remarkable eyes which this atiiiiial possesses give 
it a very odd appearance. They are pla(;ed at the extremity of club-shaped stalks, cavAi of which 
is nearly 2"""' long. The distance between the eyes is 4.7"'"'. In jjassing to tiu^ adult stage the 
eye-stalks are much reduced. The outer antennae have a short i)eduncie; along scale, aimed 
with stilV hairs on the inner margin, and a long llagellum, all very much as in the adult i)rawn. 
(PI. XII, and J'l. xiii, Figs. 40, 41.) The lirstpair of antennai are much less like the adult form. (PI. 
XII and Fig. 4(t). Th« stalk is hmger and more slender than in the full grown condition. The 
tlagella are short, the inner one still rudimentary, and the sensory hairs are retained. 

. The carapace has developed on it a lateral furrow, which is surmounted by a conspicuous 
spine placed on either side at a jwint one third the distance from the rostrum to the jiosterior end 
of the carapace. The rostrum is short and stout, IxMit upward, and does not reach beyond a line 
passing through the vesicula auditoria. The front of the carai)ace bears also a short dentiform 
process on each side below the rostrum. These are the only indications of the future si)inous 
armature of this region of tlu^ body. The abdomen and abdominal appendages arc about as repre- 
sented in Fig. 27. The telson is a short triangular plate, garnished with short bristles, and is 
terminated by a pair of very small spines. The uropods are i)rovided with a clo.se fringe of inter- 
locking, ])lumose hairs, which are longest on the inner margin. The outer lamella is one-third 
longer than the inner and three times as long as the telson. 

The first and second maxilhe of this larva are represented in Figs. 2S and 29. In Figs. 12, 19, 
29, and .VS we have four stages in the evolution of the first maxilla, and we see that it undergoes 
comparatively little change. No trace of a palpus (endoi)odite) was seen in the specimen exam- 
ined (Fig. 29), the appendage consisting of a small inner (coxopodite) and a larger outer knob- 
shaped branch (basipodite), eacli armed with short tooth-like spines. The second maxilla hasal.so 
the adult cliaracter. (Figs. 2.S, 42.) It consists of an elongated outer jdate (scapliognathite), 
fringed with a single row of plumose hairs; a palp-like endopodite, and an innermost lobulated 
division (basipodite and coxopodite), each part carrying a few bristles. 

The first maxilliped of stage F is given in Fig. ^0. It consists of a l)asal portion (coxopodite), 
which bears an inner and larger lobe (basipodite), having bristles on its proximal border; an exo- 
podite tipped with a pair of bristles, and of an intermediate bud (endojjodite) bearing a single 
bristle. Part of the second maxillipeds is shown in PI. xi and also in Fig. .'>1 (St. F.). The 
exopodite is rudiment.ary. The outer .segments are covere<l with spinous bristles. \\'{\ see already 
a resemblance between these appendages and their adult forms. (Figs. 4.'5, 45.) The third pair of 
maxillipeds are still the largest limbs. (PI. xi, Mxp. iii.) The terminal joint bears several long 
spines. Compare with tht! adult limb seen in Fig. 4(5. 

The pereiopods are slender appendages, of which the third pair are longest, as in the adult; 
the second are longer than the first; the fourth and fifth are rudimentary. One of the first pair 
of i)ereiopods is represented in Fig. 33. This api)endage is non(Oielatt>, unlike the adult stage; all 
its segments are armed with long spines, and there is a cluster of serrate bristles on the inner side 
of the proximal end of the terminal segment, and near it a similar cluster on the next. Similar 
tufts of hair are found on the adult a])])endage. (PI. xni, Fig. 47.) The terminal .joint of the sec- 
ond thora(uc limb is shown in Fig. 32; the basal extremity of the third, the fourth, and lifth are 
given in Fig. .'54. The seconil and third pair are chelate; the fourth is rudimentary; the fifth is 
still a bud. The abdominal appendages, excepting the sixth pair described above, are all nnira- 
mous. (Fig. 27.) 



348 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

This larva is colorless, excepting large spots of reddisb pigment, distributed much as in the 
previous stage. There is a spot near the extremity of the eye-stalk and similar ones on the abdo- 
men. Some of the appendages are also tipped with brownish red. The attainment of the adult 
characters is now mainly a question of the further growth of parts already present. 

The above outline gives us a pretty complete history of the metamorphosis of Stenopus. 
Between stages B and O a lacuna occurs, but it is not difiQcult to bridge over this gap. The 
development of Stenopns is especially interesting, inasmuch as it combines certain features of the 
metamorphosis of Penreus, Sergestes, Lucifer, and the Prawns in general, but it differs essentially 
from any of them. Detailed comparisons are purposely omitted in this paper, but we will call 
attention to the apparent similarity of the second larva of Stenopus (PI. viii. Fig. 17) to the zoea 
of GalUanassa subterranea, figured by Claus.* The length iu each case is o"". He says, p. 54: 

Die juiifjeu Calliaoassa larveu besitzen beim Verlassen der Eihiillen eine ansehnliche Grijsse, sind sehr lauo;- 
gestreckt nnd tragen drei spaltiistigc Fiisspaare, vou denen sich das Vordeie schon -n-eseutlich der Foimgestaltung 
des spiiteren Maxillarfiissee nlibert. Der laiige Stirusebnabel, sowie die Bestaebehing des Abdomens, dessen zweites 
Segment mit einem besouders laugeu Kiickendorn bewaft'uet ist erriDem an die nbeu beschriebeue larve. 

which applies perfectly to the Stenopus zoea, except that the latter has th« first thoracic segment 
with its appendages, while, according to Claus, the first zoea of Callianassa has not, although his 
figure is not clear on this, point. The rostrum, eyes, antenna;, second maxilhr, and maxillipeds 
are nearly identical in the two forms. The differences are in the shape of the telson and in the 
condition of the thoracic appendages. The tail fin has a convex posterior edge, a median and two 
lateral, short spines, and eleven intermediate pairs. The rudiments of the sixth pair of abdomi- 
nal appendages show through the integument. Behind the maxillipeds, already "die kurzen, 
schlauchforniigen Anlagen sammtlicher Thoracalfiisse unter dem Integument bemiirkbar sind." 

Among the Prawns, Penseus has appajrently preserved most completely the ancestral history 
of the Decapod Crustacea, and for this reason a thorough knowledge of the development of related 
species is very desirable. 

IV. THE ADULT. 

Stenopus (Latreille). 

Cancer (Herbst). 

Palccmon (Olivier). 

Stenoprt.i (Latreille) L^ach, Desmarest, Eoux, Milne, Edwards, Adams, Dana, etc. 

Diagnosis of Stenopus hispidus (Latreille). — Body nearly cylindrical. Carapace -with prominent rostrum and 
distinct transverse groove. Outer antennse -with long, bristle-bordered scale bent under the inner antennae 
toTward the middle line. Second maxillipeds -with epipodite and long exopodite. Third maxillipeds very 
long and appendicular, isrith a rudimentary exopodite at base. First, second, and third pairs of pereiopods 
chelate. The first and second pairs quite slender, ending in small shears. Third pair longest, bearing the 
large cla-ws. Fourth and fifth pairs of pereiopods slender and nonchelate. Carpus and propodus of the same 
articulated into numerous rings. First pair of pleopods uniramous in both sexes, all the others biramous. 

Special description. — Length, 37-44™" (li-l^ inches). There is little diflerence in size between 
the sexes, but the females are usually a trifle the larger. 

Color: Body invariably white, crossed by three bands of reddish crimson. Appendages col- 
orless, excepting the third pair of i)ereiopods, which are encircled by four wide zones of the same 
color. These markings are not of uniform tint, but vary from bright scarlet to mottled orange red. 
The basal joints of at least the third and fourth pairs of thoracic legs sky blue. AntennjE snow 
white. For further i)articulars under this heading, see PI. T, and Sec. i. 

The carapace (Fig. 37) ]>resents a marked transverse fossa. It is covered with .short dentiform 
spines, largest on the front. The ro.'^trum is elevated, extending hardly beyond the basil joint of 
the inner antenuiie. It ends in a sharp terminal si)ine and carries six to seven stout, curved teeth 
on the dorsal median line, liesides a single spinule projecting downwards near the tip. From'the 
single dorsal row of teeth two similar rows diverge, extending back to the transverse furrow. The 

*C. Claiia : " Untersiicbiingen znr Erforschung der genealogiscben Grundlage des Crustaceen-Systems." Wien, 
1676. Taf. vm, Fig. 1 ; also Figs. -2-7. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 349 

rostrum also bears on each side a single row of about four teeth projecting forward. The under 
side is unarmed. Several large spines occur in the angle behind the eye and on the basal joints of 
the antennae. 

The epidermic spines, which are characteristic of the Ilispidus, tliough not confineil to this 
species, are found upon the dorsal surface of the entire body, on the third pair of perciopods and 
on the bases of the appendages generally. The first, second, fourth, and liftli iiairs of thoracic 
legs are destitute of con.spicuous spines. The spines of the carapace and anterior abdominal terga 
are bent forward ; those of the fourth, (ifth, and sixth abdominal somites and of the tail tin are 
ai>pressed, stouter, nondentilate, and ])oint backwards. 

The telsou is arrowhead-shaped; its free edges are garnished with short, closely set hairs; it 
has a median groove, bordered on either side by a longitudinal elevated ridge, bearing spines; it 
hardly surpasses the uropodal lamellae. The eyes project at right angles to the long axis of the 
body. They have dark brownish black pigment and are mounted upon short, stout stalks, covered 
with small prickles. The labrum consists of a semicircular bar, the convex surface of which points 
forward and bears two nearly median spines projecting downward. From its concave border is 
suspended a liugulate ai)i)endage, which is supported by a thin, median, and vertical plate. The 
inner antennsc (Fig. 40) bear very long tiagella, the disposition of which has already been noticed 
(Sec. I). The segments of the stalk are armed with stout denticles, and each division of the 
proximal jtortiou of the outer Uagellum or exopodite bears externally a sharp spine. 

The outer antennw (Fig. 41) possess at their base a long, narrow scale (exoi)odite), which is 
traversed by longitudinal grooves. Their inner borders, which meet in the middle line, are fringed 
with closely set hairs. The stalk or protopodite is sj^iny, and the tlagellum or eudopodite is two 
and a half times the length of the body of the animal. The mandibles (Fig. 39) bear very large 
palpi, and have blunt interlocking teeth; a transverse furrow divides the cutting surfaces of each. 
The first pair of maxilhe (Fig. 3S) consist of an inner (coxojwdite) and outer branch (basipodite), 
with a slender eudopodite. The outer division or coxopodite is thickly beset with strong sjiiiies. 
The second pair of maxillaj (Fig. 42) are furnished with an elongated plate, the "bailer" or 
scaphognathite, which is fringed with hairs, an iwuer lobulated portion (basii)oditeand coxoi>o- 
dite), and i^n intermediate eudopodite, which bears several plumose hairs at its distal end. 

The first pair of maxillipeds (Fig. 43) consist of an inner lobulated portion (coxopodite and 
basipodite), thickly studded with short bristles, an outer triangular plate (epipodite), and two 
intermediate a})pendages. The innermost of the latter (eudopodite) terminates in a stout spine. 
It consists of two segments armed without by a row of long plumose Iiairs. The whip like, 
appendage exopodite next this is twice as long and is bordered with short hairs. In the second 
jiair of maxillipeds the basil portion consists of several lobules, tufted with hairs, and a small, 
external ei)ipodite. There is a stout incurved eudojjodite, with hirsute terminal joints, and a long 
slender exopodite. A transparent lamella springs from the outer side of the proximal halt ot the 
the eudopodite, and bears plumose hairs on its free margin. 

The third pair of maxillipeds (Fig. 4G) are long and conspicuous, somewhat less slem'er 
than the first or second pairs of thoracic legs. The inner and outer borders are fringed with 
long hails. The outer border is denticulated; the distal extremities of the segments, as of the 
ischiopodite, produced into a sharp spine. The basipodite is small, bearing the persistent and rmli- 
mentary exopodite, which is a slender palp equal in length to the ischiopodite. The first pair of 
(lereiopods (Fig. 47) are small, slender, and chelate. The second jiair of pereiopods are similar to 
the first pair, but longer. 

The third pair of pereiopods, the "great chehe," differ somewhat in size, the right being some- 
times larger and sometimes smaller than the left. The chela is compressed and slightly twisted. 
There is a single row of stout regular denticles, forming a saw-tooth edge on either margin of the 
•'palm," and several rows of lesser spines on the broad sides. There is also a longitudinal groove 
extending to the base of the dactyle. The carpus is prismatic and bears about five rows of large 
teeth. The ischium is more cylindrical, but similar. The dactyle and propodus i)ossess each a 
prominent tooth, which fits into a corresponding depression. 



350 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



The fourth pair of pereiopods (Fig. 48) eud iu short bifid dactyles, the teriuiual claw bearing 
a shorter proximal one below. The propodus is superficially segmented into from five to seven 
rings, which vary in size. The right propodus may have five rings, the left seven. The carpus is 
articulated into ten to twelve segments, commonly twelve, of variable or equal size. The fifth 
pair of pereiopods is similar to the fourth, but shorter. The propodus bears from six to seven seg- 
ments, the carpus from eight to twelve. In the fourth and fifth thoracic legs the number of 
rings into which the propodus and carpus are divided difter within the above limits in difl'erent 
individuals of either sex and on the right and left sides of the same individual. The pleopods are 
all biramous, excepting the first pair, in which the endopodite is suppressed as shown iu Fig. ii. 
This pair of appendages is much smaller in the male. In the female the first swimmerets are 
nearly as long as the following pairs and are fringed with long setae. 

Measurements (in millimeters). 

[Locality: Nassau, New Providence, Bahama Islands.] 



Sex - 

Length from tip of rostrum to end of telson 

Length of carapax, including rostrum 

Greatest breadtb, including spines 

Greatest depth, including spines 

Length of rostrum 

Distance between transverse furrow and tip of rostrum 

Length of first abdominal tergum 

Length of second al)dominal tergum 

Length oftliinl abdominal tergum 

Length oi loiutli abdominal tergum.. 

Length of fifth abdominal tergum 

Length of sixtli abdominal tergum 

Length of telson 

Gratest breadth of telson 

Length of «,ve-stalk 

Greatest diameter of eye 

Breadth between eyes 

Stalk of inner antenn;e 

Length of terminal segment of the same 

Length of inner fiagelliim of tlie same 

Length of outer fiagelluni of the same 

Length of sea le of outer autennie 

Greatest breadth of the same 

Length of stalk of outer anteuuie 

Breadth of stalk oi outer antenn* 

Length ot ilagellnm of outer anteMuse 

Bre.adth of llagellum of same at inner end 

Length of Ihiid maxilliped 

Length of terminal joint of the same 

Length uf basal joint of the same 

Breadth of basal joint of the same..l 

Length of exopodite of the same 

Length of first pereiopod 

Length of propodus of same 

Breadth of propodus of same 

Length o£ daetyle of same 

Length of cari>us of same 

Length of second pereiopod 

Length of propodus of same 

Length of dactyle of same 

Breadth of i)ropodus of same 

Length of carpus of same 

Length of meros of same 

Length of left third pereiopod 

Length of chela 

Greatest breadth of same with spines 

Greatest depth of same with spines 

Length of dactyle 

Width over tooth of dactyle 

Linglh of carpus of sam« 

Greatest lireadth of carpus without spines 

Greatest breadth of carpus with spines 

Length of meros of same 

Length of right third pereiopod 



37 
14. 

8 



:! 
a. 

4. 

8 

3 
:{ 

M 
6. 

45 
1 

73 

75 
it 
1. 
1. 
1. 

9-J 
0. 

18. 
•2. 
5 
1 
5 

20 



6 

27 
6, 
3 
1. 
9 
7 
48 
19 
5 
3 
7 

a. 

9. 

3 

4 

U 

46 



i. 5 



43 
16 
10 
10 



10 
1.5 
3 

5. 5 
3 
3 

5.5 
9 
4 



7 
3 
•> 

11 

8 
53 
22 

6 

4 

9 

2.5 
12 

3 

4 

12 
51 



44 



44 



40 



86 

98 



119 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

Measurements (in millimeters), — Contiuued. 



351 



Sex. 



Length of cbela of tlio same 

(iroiitost bieuiltli of stiuio with spines . 
(ircitcMt (li'pth of 8;iiius witlioiit spines 

Lenjith of dactyle of same 

Wiiith over tooth of dartylo 

Lenf;th of carpns of ri^ht tliinl pereiopod 



18 
5 
t 
7 
2 

i) 



fireatewt l)reailth of Name with spines . I 

(irealest l>reailtli of sauio without spines 3 

Length of nieros of saniu „. 12 

Length of foiirtli peieiopoil 'id 

Length ofdactylo of same l.f) 

Ldiigtli of piopodns of same 5 

Niiinber of riuj;.s in propodus 5 

Length of carpns of same 14 

Number of rings in carpns 12 

Length of meros of same.... 10 

Greatest breadth of meros 1.4 

Length of fifth peroiojiod 30 

Length of proijodns of same.. 5 

Number of rings in propodus '. 6 

Length of carpns of same 15 

Number of rings in carpus 13 

Length of meros of same 0.5 

Length of lirst pleopod 3 

Length of third jileopod 

Length of inner hiniella of same 4 

Breadth of inner lamella of same 1.5 

Length of outer lamella of same 4 

Length of inner Lamella of uropod 6.5 

Length of outer lamella of uropod - 7 

Greatest breadth of outer lamella of uropod 3 



9 


cf 


? 


.i 


19 
'I 




















, 








11 
4 

3 
12. 5 
































1.5 








5 

5 

18 

12 

11 














































6 

6 

IG 

12 

11 

7 

9 

6 

2 

6 

8 

9 










































































3 5 

















Remarks. — The earliest figure of Stenopus liispitliis with which I am acquainted is that of 
Olivier, published in ISll under the name of Palwmon hispidus (1, PL 19, Fig. 2). In this drawing 
the third thoracic leg of the right side is represented as rudimentary. In explanation of this lie 
says": "La pince gauche manquoit et paroissoit repousser. Dans uu autre, c'etoit Iadn)ite<iui 
manquoit et paroissoit repousser de uieiue." The next drawing appears in Milne Edwards's Atlas 
(3, PI. 25, Fig. 1.'}) of 1837. Like Olivier's plate this is crude and faulty. 

A second and very much better likeness of the Elispidus by Milne Edwards came out in 
Cuvier's Le Rogne Animal (4, PL 50, Fig. 20). This is represented as pale straw (n)l<)r and was 
evidently made from an old alcoholic specimen. Some of the parts are also figured. Adams's 
figure (5, Tab. xii. Fig. 6), alreadj- noticed, and his brief description agree essentially with the 
Nassau form. The antenuie are not in their natural position, and should probably be more 
than twice as long as represented. Of the habits of the species ho says : " The Stenopus, Sicy- 
ouia, and Pena'us, usually swim in a slow, deliberate manner forwards, and occasionally with 
a sudden jerk propel themselves backward. They keep at a considerable distance from the shore 
and seem to love deep still water, never ai)pcariug when the surface of the sea is riiftied." 
The drawing by Dana (6, PL 40, Fig. 8) represents the antenna' of this animal for the first time 
in a natural position. The antennal and antennular stalks are, however, much too slender, com- 
pared either with Adams's figure or with the Nassau form. The length is given as 3 inches, while 
the Steuoi)US on the plate measures about 2J inches. So far as it goes his description agrees in the 
main with my own. He says: "The legs of the first and second pairs and of the fourth and fifth 
are colorless, and they are extremely slender, much more so than in the drawings hitherto giving 
of the Hispidus ; third pair is about one-fourth longer than body, fourth joint of .second pair nearly 
twice as long as hand; fourth joint of fourth pair 12-joiuted, and fifth joint 7-joiuted; tarsus 
minute (p. 600)." 

This extreme sleuderiiess does not appear in the specimens examined by me, nor is it apparent 
in Adams's figure, which is one of the previous drawings referred to by Dana. In making the 
drawing of the Nassau Stenopus (PL v) great pains were taken to represent all the appendages 



352 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

in their natural positions, and in their true relative proportions. In Adams's i)late the fourth 
joint of the fourth thoracic leg has lG-17 rings, the liftli joint 8 rings. In the Nassau forui'the 
carpus has 10-12, the propodus 5-7 rings. In details like this, where the right and left sides of 
the same individual are often unlike, it would be surprising to find agreement. Von Martens's 
short notice of the Cuban occurrence does not give us much additional knowledge, but there is uo 
doubt that the alcoholic specimens examined by him belong to the same species as that described 
in this paper. He says : " Ich weiss keinen erheblichen TJnterschied zwischen diesen cubauisehen 
Exemplaren und den indischeu anzugebeu, welch letztere ich bei Amboiua gesammelt habe. * 
* f Nur erscheinen die indischeu im Leben bunt roth gezeichnet, in Spiritus blass orange und 
melir hartschaiig, endlich scheint Carpus un<l Hand des dritteu Fusspaars bei ihnen minder vier- 
seiiig, doch ist dieser letztere Unterschied gering und fliesseud." He then add§ that he would 
not be Burpiitied if it should turn out that the West Indian form was specifically difterent from the 
East Indian. 

So far then as we can judge from the figures and meager descriptions in our possession, the 
Asiatic Stenopus hispidus cau not be regarded as specifically distinct from the American form. 
Perhaps a point of diflereuce worthy of remark is the length of the body from rostrum to end of 
telson, which is given as 2^ and 3 inches by Adams and Daua respectively. None of the Nassau 
specimens which I have measured were more than IJ inches long. The data upon this point are not 
conclusive, and, in view of our knowledge of local variations iu this respect, cau not be regarded 
as of much importance. It is hoped that the descriptions and measurements which are here given 
will aftbrd a basis for future comparisons with the Pacific Stenopus hisjiidus. 

List of species. 

So far as I can learn, only five species of the genus Stenopus (Latreille) have been described, viz: 

(1 ) stenopus hispidus {Lair.) : 

Distribution : (n) ludian Ocean, Borneo, and Philippines (Adams). 

(6) Paumotu Islands and Balabac Passage, north of Borneo (Dana). 

(c) Amboyna, Cub^ (Von Martens). 

(d) Abaco and New Providence, Bahama Islands. 

(c) " Red Sea, ludian Ocean, ludian Archipelago, New Guinea " (de Man). 

(2) Stenopus spinosus (Risso) : 

Mediterranean (Heller), teste Von Martens and de Man. 

(3) Stenopus enmferus (Dana): 

Fiji Islands. 

(4) Stenopus semilwins ( Von Martens) : 

(Oue specimen in the Berlin Zoological Museum, purporting to have come from the West Indies. Length IS""". 
Von Martens.) 

(5) Stenopus tenuirostris (de Man) : 

Amboyna: Length 24"™. (More closely allied to Stenopus spinosus of the Mediteranean than to Stenopus 
hispidus, and is the representative of the former in the Indian Ocean ; de Man.) 

STENOP08 LITERATURE. 

(1) Olivier: Encyclop^die M^thodique, Hist. Nat. Insectes, t. viii, p. 666, 1811. 

(2) Latreille : Encyclop^die M^thodique, Hist. Nat. Crustaces, Arachnidses, et Insectes, t. 10, Paris, 1882. 

(3) Milne Edwards, H. : Hist. Nat. des Crustaces, t. 2, p. 40(5, 1837. 

(4) Milne Edwards, H. : Le Rfegne Animal, Cuvier ; Les Crustaces, with Atlas, by Milne Edwards, p. 137. 

(5) Adams and White: The Zoology of the Voyage of H. M. S. Samarang, 1843-6, p. 61, Loudon, 1850. 

(6) Dana, J. D. : U. S. Exploring Exped. U. S. N., 1838-1842, vol. xiii, pt. 1, Crustacea, p. 607. 

(7) Martens, E. V. : Ueber Cubanische Crustaceeu ; nach den Sammlungen Dr. J. Gundlach. Archiv. f. Naturgesch., 
38. Jahrg., Bd. 2, 1872, p. 143. 

(8) Belter: Crustaceen des siidlichon Europa, S. 299. (1 have seen only references to this paper.) 

(9) De Man, J. O.: Bericht iiber dieim indischeu Archipel von Dr. J. Brock gesammelten Decapodeu und Stomato- 
poden. Separat-Ausgabe .ins dem Archiv. f. Naturgesch., 53. Jahrg., pp. 215-600, 17. Taf., Berlin, 1888. 



CHAPTER III. 

THE HABITS AND METAMORPHOSIS OF GONODACTYLUS CHIEAQRA. 



By W. K. Brooks. 



(With PI. I, III, XIV, and xv.) 

The Structure and Habits of the Adult. 

This well-known species is t'outid alou;^ the shores and islands of all tropical and subtropical 
seas, and our collections contain si)eciiiions from tlie Atlantic, the Pacific, and the Indian Oceans. 
Among the many localities where its presence has been recorded the following may be named: 
Bermuda, Florida Keys, Bahama Islands, Cuba, St. Thomas, Brazil, Mediterranean, Cape St 
Iloqne, iSaniboanga, Samboanga Banks, Nicobars, Bed Sea, Auiboina, Indian Ocean, New Gninen. 
It is subject to but little variation, notwithstaudiug its ver.y wide distribution, and also notwith- 
standing the fact that there are several other distinct species of Gonodactylus extremely similar 
to chiragra, and distinguishable from it by only very minute differences. There is a well-marked 
ehiragra-like group of species all so close to each other that their divergence from each other must 
have been comparatively recent, and in view of this fact it seems remarkable thaf one of these 
spe<;ies should so persistently retain its identity when exposed to such a wide diversity of 
conditions. 

The species may be thus characterized : Stomatopoda with the sixth abdominal somite sepa- 
rated from the telson by a movable joint; the hind body convex; and the dactyle of the raptorial 
claw without spines and enlarged at the base ; rostrum consisting of a transverse proximal portion 
more than twice as wide as long, with subacute antero lateral angles and a slender, acute median 
spine which does not quite reach to the bases of the eyes ; carapace nearly rectangular, three lifths 
as long as wide, leaving the dorsal surface of the second thoracic somite completelj' exposed ; au- 
tero-lateral angles semicircular and projecting beyond the median gastric area, which is nearly Hat, 
and bounded by two nearly parallel gastric sutures, which are continued to the posterior edge of the 
carapace, which is nearly transversa with rounded posterolateral angles; the transverse cervical 
suture is faintly marked, distaiic from the anterior margin about two-thirds of the length of the 
carapace; secoiul thoracic sonflte, somewhat narrower than the carapace, with acute lateral angles; 
the eight following somites ecpnil in width and wider than the carapace; the third, fourth, aiul 
tifth thoracic somites about e()ual in length ; the lateral margins of the third are straight, with 
rounded angles, and as wide as the dorsal jiortion ; the fourth is narrowed a little towards the 
lateral edge, and the fifth still more so ; dorsal surfaces of the free thoracic somites and of the first 
five abdominal somites smooth ; hind body <!onvcx ; all the abdominal somites have marginal lateral 
cariuic, which are nearly linear, with the anterior end only a little wider than the posterior end; 
posterolateral angles rounded in the first four abdominal somites, rectangular in the fifth, and 
acutely pointed in the sixth; there are no dorsal carina* on the first five abdominal somites, and 
no median dorsal (carina on the sixth, which carries three pairs of swollen convex lateral carinie, 
which are equal in length and end posteriorly in acute spines, which are occasionally wanting 
on the submedian pair; the external carina is much less swollen than the others, and it unites 
at its posterior end with the laterial marginal carina; the spines of all the carina project bejond 

the posterior edge of the somite and lie in the same transverse plane. 

353 
S. Mis. 94 23 



354 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

The fifth abdominal somite is somewhat longer than those in front of it, and about twice as 
long as the sixth. The telson sometimes presents. slight variations, but most of its characteristics 
are well marked, so that there is usually no difficulty in distinguishing the species by examining it. 
It is considerably wider than long, and its median portion is occupied by a rounded prominence, 
which consists of three broad, convex rounded carinas, none of them ending in spines ; the median one 
is longer than the others and spatulate at its posterior end, while the others have both ends obtusely 
rounded and alike ; external to the proximal end of each lateral carina, and almost directly under the 
tip of the second, or intermediate dorsal carina of the sixth abdominal somite there is a small polished 
hemispherical tubercle. The edge of the telson is folded into six teeth, of which the submedians 
are largest and project I'arthest backwards; the tips of the intermediates are distinct and reach 
about halfway to the tips of the submedians; the laterals are obsolete on the dorsal surface, al- 
though thin, small tips are distinctly visible on the flat ventral surface of the tel.son ; each of these 
six teeth carries a dorsal carina ; that of the lateral is marginal and nearly linear, while the otljers 
lie in the dorsal axes of the teeth and are thick and convex; that which lies above the submedian 
tooth is short, and lies in the same longitudinal plane as the external carina of the median promi- 
nence of the telson, while that which lies above the intermediate tooth runs nearly to the anterior 
edge of the telson; the median edges of the submedian teeth are minutely serrated, slightly con- 
cave, and meeting at an acute angle. There is a minute, nearly obsolete, tooth in the angle be- 
tween the submedian and the intermediatei, and the tips of the submedians are occasionally, but 
exceptionally, tipped by movable acute spines. The dorsal surface of the basal joint of the uropod 
ends posteriorly in an acute spine with a small lobe on the outer side of the base: its ventral sur- 
face ends posteriorly in a curved process divided into two acute curved spines, of which the outer 
is much the stouter and usually considerably longer than the inner, although they are occasionally 
nearly equal ; the outer one has no marginal tooth. The paddle of the exopodite is about half as 
long as the second joint, which carries a central terminal immovable spine, and usually eleven — 
rarely twelve, and still more rarely ten — movable spines, of which nine are marginal and the tenth 
and eleventh fermiual, largest, and central to the paddle. The ej'es are cylindrical, with rounded 
corneajj and the first and second antennae are about equal in length, and more than half of tUe 
second joint of the shaft of the first antenna is exposed in front of the eye. 

In the Bahama Islands this species presents two well-marked color variations, which occur 
side by side, specimens of both sorts being often found in burrows less than an inch apart. In the 
one form the color is a uniform dull-olive without spots or markings of any sort, as shown in PI. iii; 
while the other form, which is copied in PI. 1, Fig. 2, is more transparent and is delicately mottled 
over the entire dorsal surface in an intricate but constant i)atteru of greyish-green i)igment so 
distributed as to form three transverse bands across the carapace and the large joints of the 
raptorial claws and fine transverse bands across the telson, while over the rest of the dorsal 
surface it forms a complicated reticulum. This difference is not sexual, for I Ibund both males 
and females of each color; nor is it distinctive of age, for, while all the largest specimens were of 
the uniform green color, I found specimens of each color of all sizes except the largest. It is not 
probable that there are two constant color varieties living side by^ide in the Bahama Islands, 
and I am disposed to think that the mottled transparent specimens are those which have recently 
moulted, and that the color becomes more uniform as the cuticle hardens. 

In the Bahama Islands this species inhabits burrows which it constructs in the coral rock or 
in masses of coral in shallow water, and, as nearly all the localities where its presence has been 
recorded are in the coral area, it is probable that this habit is pretty generally retained by the 
species all over its habitat. I have found it most abundant in lagoons and sounds on shelving 
beaches which are bare or nearly bare at low tide; and when a beach of this description is over- 
liung by a limestone cliff', from which fragments fall into the water, each fragment is honeycombed 
bj^ their burrows. A crack or natural depression in the rock seems to be selected bj- the animal 
when about to construct a new burrow, for most of the burrows opened into such cracks. The 
mouth of the burrow is nearly circular and only a little larger than the body of its inhabitant, but 
just within it widens out into a flask-shaped cave (PI. iii), with smooth, even walls and regular 
curvature, and large enough for the animal to coil up or turn around inside it. Most of the burrows 
are horizontal, but many are vertical with the opening below, and a few are vertical with the 
opening above. 



MEMOIRS OF TUE NATIONAL ACADEMY OF SCIENCES. 355 

The iinimals usually rest coiled up, with the eyes and aiiteiiiiie directed outwards, just within 
the month of the burrow. They are always ou the alert and rraili out and snap at every small 
animal which aj)pr<)aclies, even when it is two or three times larfjer tiian the (ionodactylns. They 
rarely jinrsue tiieir prey, at least iu the day time, and while a bait held near the mouth of the bur- 
trow will usually tempt them as far out as the body can be stretched without leavinjr the burrow 
they seldom <^o any further. In aquaria they are much more active at ni<jht than in the daytime, 
and they may possibly wander more in scantli of i)rey at niiiht tiian I luive ever seen them do in the 
daytime. They are solitary iu tiieir habits, and 1 have never found two in the same burrow. They 
are pugnacious to an astonishing degree, and their tighting habits, as I have observed them iu 
aquaria, are so lixed and constant tiiat they niust he constantly exercised by the animals when at 
home. When two specimens are placed together in an aquai-ium they at flrst a[>pear to be uu- 
conscious of each other, but more careful examination will show that their eye stalks are iu con- 
stant motion following each movement ol' tiie enemy. Tiiey soon assume a position in whi(;ii they 
are face to face, ahiiongh they may be on oi)posite sides of the aquarium, and the c(»ustaut motion 
of their eye stalks shows how intently each movement is watched. Sooa one attempts to get be- 
hind the other, but each such attempt is frustrated, until fiually they are brought close together, 
face to face, and soon one s[irings suddeuly upon the other and attempts to pinch some unprotected 
part. They then spring apart and eye each other again to repeat the attack at short intervals 
until one is disabled; the other then springs upon him and soon tears him limb from limb, dis- 
jointing all the free somites of tiie boily and tearing out and devouring the flesh. 

I was not able to learn how the burrows are made, for none which I kept in captivity made 
burrows. The regularity and smoothness of the burrows and their adajjtation to the shajjc and 
size of the body indicate that they are constructed by the animals themselves. The habit of bur- 
rowing iu hard rock instea<l of soft nind is a fortunate one for the naturalist ; for, while it is almost 
impossible to obtain the eggs of an ordinary Stomatoiwd without using a steam dredging machiue; 
it is easy to get those of Gouodactylus by breaking up the rock iu which it lives. 

While adult Stomatopods arc al>undant and widely distributed, their eggs are almost unknown, 
for most of them inhabit deep burrows under the water, where it is no easy matter to capture the 
adults, and even when these are caught they do not carry eggs even in the breeding season, for 
the eggs are not fastened to the appendages as they are in most Crustacea, but are deposited at 
the bottoms of the inaccessible burrows. As they are dependent upon the aeration which is pro- 
duced by the current of water which the parent ])umps through the burrow by means of the valve- 
like paddles of the abdomiual feet, they die when deprived of this current. The eggs are sometimes 
obtained, but unless they are found in an a<lvauced stage ot ilevelopment it is dillicult to rear 
them, and 1 know of no Stoinatojmd which has been reared from the egg under observation except 
the Bahama OoiiodacUjlus chiragra. As the pelagic larvte arc large and conspicuous they are 
often captured at the surface of the ocean iu the tow net, and the numl)er of genera and species of 
Stomatopod larvie which have been described is nearly equal to the number of adult species which 
are known, and the o|)portunity to identify even one of these larvse by actually rearing it from the 
egg is a most noteworthy and important occasion. 

The habits of the Bahama tlonodactylus attord this opimrtunity ; for the nature of the rock 
which it inhabits prevents the construction of a deep burrow, and as the fragments of rock may 
easily be c.irried ashore and broken up the eggs can be obtained without difticulty. At the time 
of my tirst visit to the Bahamas I was engaged in correcting the proofs of my report on the Chal- 
lenger Stomatopods, and one of the motives of the expedition was the hope that I might possibly 
obtain Stomatopod eggs. A day or two after our arrival Dr. E. A. Andrews brought me a Gouo- 
dactylus and a bunch of yellow c^ggs, which he had i)icked out of a rock which he had broken to 
l)ieces while searching for Annelids. The eggs were newly laid, and, while they were obviously 
those of some crustacean, there was no evidence that they belonged to Gonotlactylus except the 
fact that they were found among tiie fragments of a rock whi(;h also contained this apinial. As 
soon as I saw the eggs and heard how they had been obtained 1 started for a point where the 
beach was covered with fragments of coral rock. It was then late in the afternoon and growing 
<lark, but I waded into the water and carried ashore as large a rock as I could lift. After I had 
thrown this ou to a larger rock and broken it to pieces there was just daylight enough to show me 



356 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

the GoDodactyli scattering in all directions, and the masses of yellow eggs which were spattered 
over the large rock which I had used as an anvil ; but the problem was solved, and I went home 
and to bed, confident that I should next day get all the embryological material I needed. 

As shown in PI. iii, the animal molds or shapes the mass of eggs into a hemispherical cap, 
which fits over the convexity of the hind body and lies between it and the stone wall of the bur- 
row. The parent reaches out to snatch at passing j)rey, but so long as she is undisturbed she 
remains in the burrow. When the burrow is broken open she quickly rolls the eggs into a ball, 
folds them under her body in a big armful, between the large joints of her raptorial claws, and 
endeavors to escape with them to a place of safety. The promptness with whicli this action is per- 
formed would seem to indicate that it is an instinct which has been acquired to meet some danger 
which frequently presents itself. It would seem as if a cave in a solid rock were a pretty safe 
refuge from all enemies except a naturalist with a geological hammer, and it is difficult to say 
what the accident is which has thus been provided against. The larger beads of growing coral 
are often broken off by the waves, and loose fragments of rock are overturned by severe storms, 
and it is possible that, when alarmed by a violent shock, it flees from its cave to escape the 
danger of being crushed when the rock is torn from its place and turned over. At any rate its 
habit is the i-everse of that of most burrowing animals, for they usually retreat to the depths of 
the burrow when alarmed. This is true of all the Stomatopods which I have had an opportunity 
to obsers'e except this species, and the chief use of the burrow of t'^quUla empusa is for refuge in 
danger, while LysiosquiUa excavatrix darts down its burrow at the least alarm and can not be 
driven out even when the sand has been dug up on all sides of it. 

The Metamorphosis of Gonodactylus chieagra. 

That feature of the life of Stomatopods upon which new data are most to be desired is the 
history of the early larval stages, and an abundant supply of the eggs of GonoductyluH chiragra 
rendered it an easy matter to obtain this history for that species. I also obtained a complete series 
of eggs for studying the embryology, but, as a few preliminary sections showed that this was of 
slight interest and that there is no essential ditterence from other Macroura as regards the egg 
embryology, this subject was not studied. 

Most of our knowledge of the metamorphosis of Stomatopods is based upon the comparative 
study of collections of alcoholic specimens, and the direct observations on living larvae are very 
scanty. In 1SS2 Faxen published an account (Selections from Embryological Monograi)lis com- 
piled by Alexander Agassiz, XA^alter Faxon, and E. L. Mark, I Crustacea, Cambriilge, 18S2, Bull. 
Mus. Com]). Zotil., Vol. ix. No. 1, PI. viii. Figs. 2 and 3) of observations made three years before 
upon a young Squilki empusa which he had reared from an Alima larva; and in a par|)er which 
was published iu 1870 I described (On the larval stages ol' Squilla cmpiisa) a sei'ies of similar larv;B 
which I had studied while they were alive, and which was suthcieutly complete to warrant the 
statement that they were the young of SquiUa empusa, and that this species probably hatches from 
the egg iu the Alima stage. In my report on the Challenger Stomatopods (IJeport of the Scientific 
Results of the Voyage of H. M. S. Challenger during the years i87o-7tJ, xvi, part XLV, I8SG) I 
have given an account of the metamorphosis of Lysiosquilla excavatrix which I had reared at 
P>eaufort, N. C. : but except for these observations our knowledge of Stornatopod metauior|)hosis 
rests upon the comparative study of preserved specimens, and, while the series which are picked 
out from miscellaneous collections sometimes present pretty satisfactory evidence as to the adults 
which they represent, this sort of indirect evidence can not be conclusive. 

Large and varied collections of larvie have been compared for the purpose of selecting those 
which form stages in the same series, and of ascertaining as accurately as possible the adult aflini- 
ties of theoldest larva-, by Claus (Die Metamorphosen der Squilliden, Abhandl. d. I: Gesellsch. d. 
Wiss., Gottingen, Bd. xvi, pp. 1-55, Pis. i-viii, 1871) and myself (C'/(«7/e«(/e/- Rep., pp. 81-11-1). My 
own report was, so far as this subject goes, a supplement to Claus's work, for in its preparation I 
availed myself of his methods and results, amplifying and completing many of his observations, 
and confirming some of his results and correcting others. Combining his work with my own, I 
devoted a chapter of my report to the discussion of the larviB, and gave a scheme or outline of 
the probable metamorphosis of each genus of adult Stomatopods. 



V. 



MEMOIRS OF THE NATIONAL ACADEMY OE SCIENCES. 357 

Stomatopod larvae or Ericbtliida;, as tbey were named before their larval uature was susi>ected, 
bave been divided into four {jeiiera, Erichtlioidina, Ericlitlius, iiquillcriclithiis, and Alima. Of tbese 
four the first, Ericlithoiilina, is siniidy a .yoiuifjcr staj^e in the life of the Ericlitlnis, and the third, 
Sqitillcriclitlius, a fnll.v-frrown larva, of the Erichflntu type, so that the genera hecoine reduced to 
two, Erichthns and Alima. Of these two fjenera, one, Alitna, is much more sbari)ly defined than 
tlie other, ^/Jc/iY/iKS, which contains a number of diverfjent types, of which 1 have shown that 
five may be clearly distinguished, and I have j)roi)osed, for these five, nauies which indicate the 
adult genus to which each corresponds. I have shown tiiat there are many reasons for believing 
that all Alimi are (iquilla larvie; Alimerichthus, tlie larva; of Cliloridella; Ericlithalinia, the larvae 
of Corouidd ; Lysiericlitlins, the larva', of Lysiosqnilla, and I'.seuilerichtlius, thi', larvae of rxciidi)- 
squilla. Tiie remaining larval type may be distinguished from the Li/sirrivhthus by tiie shallow- 
ness of its caraiiace, which is not at all infolded, and by the position of its postero lateral 
spines, whicli arise very close to the dorsal middle liiu'; while it may be distinguished from the 
Pseitdertclithus larva^ by the length of the [)osterolateial s[)iues, which are at least half as long iis 
the carapace, and also by the fact that the telson is wider than long and longer than the long 
outer spine of the nropod. For this larval type, which was represented in the 67(a//e«//er collec- 
tion by many specimens, I ])roposed the name Gonerivhthm, giving, at the same time, many 
reasons for regarding it as the larva of the genus Gonodactylus. Several of these larvai were 
selectetl and shown in Tl. xir, Fig. 5, PI. xiii, Fig. !), and Tl. XV, Figs. I and 5, of my report; and 
I pointed out that in ail of these larvae, as in the young (louodactylus, the sixth abdominal .somite 
has a pair of submedian spines near its i)osterior eilge, and its posterolateral angles are i>rodnced 
into acute spines. The telson is .slightly wider than long, and its submedian spines are long and 
slender, but shorter than they are in Pseuderichthns. The telson is notched on the middle line, 
and there are from fourteen to twenty small secondary spinnles on its posterior edge, between the 
submedians. There is one small secoiulary spinule internal to the base of the lateral marginal 
spine, another internal to the base of the intermediate,^ud a third miJway between this and the 
submedian. 

In ri. XV, Figs. 5 and 0, of my report, as in the young Gonodactylus, the outer edge of the 
proximal joint of the exopodite of the nropod is fringed by nine marginal spines, the terminal one 
lont^est, and the outer si)ine of the basal i)rolongation is mnch longer than the inner, but not so 
li'hg as it is in Pxcudcrichthuii. A com])arison of the telson of the young Gonodactylus with that 
of the other larval types will show that the one now under discussion is the only one which exhibits 
this resemblance, and as this larva never exhibits any traces of marginal spines on the dactyle of 
the raittorial claw it nnist pertain to some known adult with an unarmed dactyle or else to a new 
genus. It is not probable that a larval type which is so common pertains to an unknown adult 
genus. The larvaj are not ProfosquUla; as this genus has the telson fused with the sixth abdom- 
inal somite, while it is free in the older larvic; nor are they PHeudt)squiUa\ for they have no movable, 
spinnles on the tips of the submedian spines of the telson; and as all the other genera of Stoma- 
topods except Gonodactylus have the dactyle armed, the only remaining genus is Gonodactylus, 
anil the structural characteristics of the oldest larv;n imlicate that they are the young of species 
in this genus. 

Led by these considerations I did not hesitate to speak of the.se larvie, in the Challcnf/er 
report, as Gonerichthi, or young Gonodactyli, and to give this larval form as one of the diagnostic 
characteristics of the genus. This determination rests, however, ui)on circumstantial or indirect 
evidence; and, while the evidence is quite conclusive, I was nevertheless ])leased to obtain more 
l)Ositive proof from the larvse which I reared from the eggs of Gonodactylus chirnfira. 

Like many othei' Crustacea which iniiabit the (loral i-eefs, this species has its metamorphosis 
abbreviated and it hatches from the egg in an advanced condition. It is shown just before iiatcliing, 
seen from behind in PI. xiv, Fig. 1, and from in front in Fig. 2. The large yolk covers the dorsal 
surface, and the larva is doubled on itself, so that the telson and the tip of the abdomen are visible 
in a front y'wvr. The first t'lvo. abdominal somites are indicated before it leaves the egg, and the 
first five pairs of abdotnimil appendages are fully developed, although the other appen<lages, with 
the exce|>ti(in of the mandibles and the large raptorial second maxilliiieds, are either absent or rudi- 
mentary The eyes are large, and even before hatching they are movable, although they are 
nearly sessile. « 



358 MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. 

The larva, immediately after hatching, is shown in side view in PI. xiv, Fig. 3; iu ventral view 
iu PI. XV, Fig. S, and in dorsal view iu Fig. 7 of the same plate. The carapace is nearly half as 
long as the entire animal, and its posterior border, which is deeply emarginated, crosses the raidde 
Hue over the posterior edge of the tenth somite; the somite which carries the appendages which 
are usually called, iu the decapod Crustacean, the second pair of legs. There is a short, rather 
stout rostrum, and the anterior end of the carapace, which covers about half the eyes, is nearly 
semicircular. The posterolateral spines are short aud curved outwards; there are no secondary 
spines external to their bases, but there is a small median dorsal spine on the posterior edge of the 
carapace, while the anterolaterals are absent. The antennule consists of a two-jointed shaft with 
two flagella, one terminal and the other arising from the dorsal surface of the distal joint of the 
shaft. Tiie antenna consists of a rudimentary exopodite, which is cylindrical and ends iu five 
swimming hairs, although it is of little u.se in locomotion. The large eyes are subspherical, 
nearly sessile, and they touch each other on the middle line dorsal to the anteuuules. The man- 
dibles are enormous and the two pairs of maxilhe rudimentary, as are also the first pair of maxil- 
lipeds, while the second pair, the large raptorial limbs of the adult, are well develoi)ed, although 
the dactyle is not folded backwards upon the penultimate joint or propodite. The third, fourth,, 
and fifth iiiaxillipeds, corresponding to the third maxillipeds and first aud second ambulatory 
limbs of (lecapo<ls, are rudimentary, and the three following appendages are absent, although all 
the correspoiidiug somites are indicated as well as their ganglia. The abdomen is about twice as 
wide as the thoracic region and somewhat more than half as wide as the Ciirapace. The first five 
somites are distinct aud all end in acute posterolateral angles. The suture which separates the fifth 
from the unsegmented region, which represents the sixth and the telson, is obscure, aud this 
region is longer than wide. 

The abdominal appendages gradually decrease in size from the first and largest to the fifth 
pair, but all have their adult structure, except that they, carry no gills and all are functional. 
The telson has four marginal spines on e»ch side. Its posterior edge is slightly notched and car- 
ries seveu or eight pairs of minute movable spines. The newly hatched larv;e swim actively about 
by means of their abdominal feet, not by Hexing aud extending the abdomen, and uotwithstaud- 
ing the presence of a great mass of food yolk in the walls of the stomach they eat voraciously. 
By a lucky chance I found their proper food at once. Several bunches of the eggs of some 
unknown Nudibiauch were iu the a(piarium in wiiich the first brood hatched, and the larvre, nearly 
a- thousand iu all, soon settled dowu upon them, covering them completely, and at once began 
tearing them off aud eating them. When washed away from them by means of a jet of water they 
swam about the aquarium for a siiort time, but soon settled down upon the eggs again. As these 
eggs are not very abundant they can hardly be the only food of the young larvte, although I could 
fiud nothing else that they would touch, aud they refused the eggs of all other Nudibranchs. At 
this stage the heart consists of a large anterior chamber in the region of the second maxillipeds 
and a large dorsal vessel running as far as the fifth abdomiual somite, with a pair of ostia in each 
somite. 

After about sixty hoars they moulted and assumed the form which is shown in side view in PI. 
XIV, Fig. 4. The rostrum aud the spines on the posterior border of the carapace have lengthened, 
but its shape and relative size are about as before. The second antenupe are more clearly divided 
than before into a shaft and a scale, which has lost its hairs and is more flattened. The first pair 
of maxillipeds have made their a[>pearance iu the adult form, and the second pair are much larger 
thau before, and the dactyle is uow folded back onto the edge of the flatteued penultimatejoint. In 
all other respects the larva is like the younger one, but a little longer and with less food yolk. In 
about a week after hatching they molted again aud passed into the third (Erichthus) stage, which 
is shown from above in PI. xv. Fig. 1», and in side view in PI. xiv, Fig. 5. The rostrnm is now greatly 
elongated and reaches to the tips of the anteuuules. Small anterolateral spines have made their 
appearance, as well as a small spine external to the base of each posterolateral. These latter are 
greatly elongated and very slightly divergent. A great change in the shape of the carapace has 
taken place, as will be seen by comparing Fig. 7 of PI. xv with Fig. 0. Its lateral margins are 
nearly parallel, and its greatest width only a little exceeds that of the abdomen. Its posterior 
border is uow nearly transverse and crosses the middle line above the last thoracic somite. The 



MEMOIRS or THE 2^ATIONAL AGADEMV OF SCIENCES. 359 

sixtli :il)(l()minal somite has separated from the telson, but its appendages are not yet developed. 
The .scale of the antenna is now fringed with hairs, and the eyes are divergent, with well devel- 
oped stalks. The raptorial (jlaws have greatly increased in size and are beginning to api)roximate 
to the adult forn), while at the earlier stage they closely resembled the chela' of the third, fonrth, 
and lifth pairs of maxillipeds of an adult Stomatopod. From this time on to the end of its larval 
life the young Ericlithus of Gonodavtylus chiragra jtresents the characteristics of that larval type 
for which I have proposed the provisional name Gonerichthus: and, while the resemlilance grows 
8tro7iger as the larva grows older, it is unmistakable even now, and still clearer after the next molt, 
when it assumes the form shown in PI. xiv. Fig. (5, from above, and obliquely from below in PI. xv, 
Fig. 10. 

The anteunulary flagella are now beginning to elongate, and that of the antenna is now rep- 
resented by a bud, but there are no new appendages, although the sixth abdominal somite is now 
indi(!ated. Although it is very much younger than the Gotierichthi shown in my Ghallemjer report 
in PI. XV, Figs. 1, 5, G, aud 11, it resembles these larvie in the following features as well as in 
many minor points: The rostrum is long and reaches beyond the tips of the anteuuules, and it has 
four or five median teeth on its ventral surface. The anterolateral angles of the carapace end in 
acute spines pointing forwards, and the anterior edges are inclined towards each other, so as to make 
at the base of the rostrum an angle a little greater than a right angle. The lateral borders of the 
carapace are nearly parallel, and the posterolateral spines long, slightly divergent, and with a 
small acute spine external to the base of each. The carapace covers all the five thoracic somites 
and all or nearly all of the first abdominal, aud its posterior border is transverse. The median 
dorsal spine, which was carried on the posterior edge of the carapace of the younger larvai (Figs. 3, 
4, and .5 of PI. xiv), has disajipeared, although it persists until a much later stage in the larvje 
shown in Figs. 1, fi, and 11 of the Challenger report. The hind body is now nearly three-fourths 
as wide as the carapace. 

The lateral margins of the telson still carry, as they did during the earlier stages, four nearly 
equal marginal spines on each side; of these the most anterior is the external, the next the inter- 
mediate, the third a secondary spinule, and the fourth, which, at the stage shown in Fig. 6, PI. xiv, 
forms the i)osteroIateral angle of the telson, is the submedian. The posterior border between the 
snbmedians is very slightly notched and nearly transverse. All the Challenger Gonerichthi are 
very much older than this larva, and their telsons are more developed. The spines especially are 
much more elongated ; but in Figs. 5 and (5 of PI. xv of the report the secondary spine can be 
clearly recognlzeil about halfway between the submedian and the intermediate. 

With the assumption of the form sliowti in PI. xv. Fig. 10, the habits of the larva undergo a 
sudden change. Up to this time, while able to swim briskly about by the use of their abdom- 
inal appendages, they spent most of their time near the bottom of the aquarium, seldom going 
up more than an inch or two, although they are quite able to reach the top of the water, which 
was about 10 inches deep, and when masses of Nudi branch eggs were suspemled near the surface 
of the water they quickly discovered and fastened upon them. 

Up to this time, also, they were peaceful aud did not attack each other. Several hundred sur- 
vived the molt which precedes the beginning of their pelagic life, but all of them soon died and none 
passed this stage, which is the one shown in Fig. 10. They now left the bottom, and became rest- 
less, swimming continually at all levels in the water. They refused to touch the eggs of whi(;h up to 
this time they had been so fond, and I could find nothing else which suited their appetites, but their 
proper food is, beyond question, small swimming animals of some sort, for they now began fighting 
among themselves, and when two met they would seize each other with their raptorial claws, and 
then tumble over and over together, until they struck the bottom, when both died. The snrvivois 
would not touch the dead bodies, although most of them soon shared the same fate, aud the rest 
became weak and soon died. 

At the same time that I was studying the growth of the captive larva- 1 captured several older 
ones in the surface net, and one of them somewhat older than Fig. 10 is shown in Figs. 11 and 12. 
The third, fourth, aud fifth maxillipeds are now developed aud are like those of the adult; and 



360 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

the three pairs of free thoracic legs, and the uropods are represented by buds. An umber of moults 
and probably an interval of many weeks intervenes between this stage and the one shown in PI. xv, 
Fig. 11 of the Challenger report. 

The life history of this species of Gonodactylus, in the Bahama Islands at least, is thus seen 
to be extremely simple. It hatches as an Erichthus and remains an Erichthus until it a.ssumes its 
adult form ; and as the successive appendages make their appearance they have from the first the 
structure which they are to retain through life. The statement which I made in my Challenger 
report (p. 55), that Gonodactylus hatches from the egg in the Erichthoidina stage and subsequently 
changes into an Erichthus, is an error, at least so far as Gonodactylus chiragra is concerned, 
although it is possible, in view of the great variation which we have observed in a single species 
of Ali)hens, that in other regions, where the adults have diflerent habits, the larva may hatch in a 
younger stage. Coral-dwelling Crustacea seem to exhibit a tendency towards the abridgment of 
their metamorphosis, and it is not .at all improbable that other species of Gonodactylus may have 
an Erichthoidina stage. 

The Challenger collection contains a bottle of very minute and young larva- in the Erichthoi- 
dina stage, and one of these is shown in Fig. 3 of PI. xii of my report. Comparison between this 
and the newly hatched Erichthus of our species, PI. xiv. Fig. 3, will show many points of resem- 
blance, and future research may possibly prove that it is the larva of Gonodactylus, although the 
statement that all Gouodactyli hatch as Erichthoidiuaj is an error. 



CHAPTER IV. 

THE METAMORPHOSIS OF ALPHEUS. 



By W. K. Brook and F. H. Hebbick. 

_A 

(With Pla. I, II, IV, XVI to XXIV ) 

Section I.— The Metamorphosis of Alpheus minor from Beaufort, North Carolina. 

This small species is found in abundiince at Beaufort, Nortli Carolina, and in the Bahama Islands, 
and it is no doubt widely distributed alonfr our southern coast. At Beaufort it is found in shallow 
vertical burrows in the sandy mud which forms the bottom of most of the landlocked sounds 
between tide marks. It is also met occasionally in shells, and under loose stones and oyster 
shells. 

Durinji its development, between the time when it hatches from the egj? and the time when it 
acquires the adult form, it i)asses through a long metamorphosis, divided into many stages. Its 
life history has been traced by one of the authors at Beaufort, and by the other at Nassau, and the 
individuals from both these localities pass through exactly the same series of changes. As we 
also lind that other species, such as Alpheus iiormani, i>ass through the same metamorphosis, the 
life history of Alpheun minor may be regarded at the primitive or ancestral life history of the 
genus, which originally characterized all the species ; although it is now retained in it.s perfect form 
by only a few, aud has undergone secondary or recent modilications in the others. 

THK FIRST and SECOND LARVAL STAGES. 

The stage in which the larva hatches from the egg is of very short duration, as it molts and 
passes into the second stage within a few hours after hatching. No drawings of it were made 
before the change, but this is very slight, and the description of the second stage holds true in all 
essentials of the first stage, except that the tips of the cxopodites of the three pairs of nuixillipeds, 
and the plumose hairs on the antennules and antenna' are not fully extende<l until after the change. 

The second larval stage is .shown in PI. xvi, Fig. 2, and in PI. xvii, Fig. 2, and various organs of 
the larva during the lirst stage are sliown in PI. xvi, Figs. 4,0, 7, and 8, and IM. xviii, P'ig. 4. In 
PI. XVI, Fig. 4, is the antenna of the first larval stage. Fig. 6, the first maxilla, Fig. 7, the second 
maxilla, Fig. S, the mandible, and Fig. 4 of PI. xviii, the first maxilliped. As shown in PI. xvii. 
Fig. 2, and in PI. xvi. Fig. 2, the locomotor organs of the larva during the first and second stage 
are the plumose exopotlites of the antenna' and of the three pairs of maxillipeds. There are uo 
functional ajipendages posterior to the maxillipeds, and the large eyes are freely movable and 
entirely uncovere<l. 

The larva has all its appendages fully develoi)ed and functional as far ba<;k as the third pair of 
maxillipeds. Following these are three bud like rudinuuits of the first, second, and fifth i)airs of 
thoracic limbs, aud j)osterior to these a long tapering abdomen, divided into six segments, there 
being at this time no joint between the telsou and the sixth abdominal segment. During the first 

Ml 



3(52 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

stage there are no traces of any abdominal appendages, but in the second stage, the outlines of 
the sixth pair are faintly visible under the cuticle of the telson, as shown in PI. xvi, Fig. 2. 
The stomach is almost completely free from yolk, and the surface of the body is marked by 
red and yellow pigment spots, which are very constant in position and number, and are well shown 
in the figures. 

As shown in PI. xvi, Fig. 2, the antennule consists of a stout shaft composed of a long basal 
portion with no trace of an ear and a much shorter distal joint, which carries externally a much 
shorter and smaller joint with four sensory hairs, and internally a long slender plumose hair, which 
is not fully extended until after the first moult. At this stage this hair is almost sessile upon the 
shaft, although its base is destined to give rise to the long flabellum of the antennule of the 
adult. 

The antenna has a large exopodite, which is fringed with plumose hairs, and is an efiScient 
organ of locomotion. During the first larval stage this e.xopodite, which is destined to become 
the flat scale of the adult antenna, is cylindrical and distinctly annulated, as shown in PI. xvi, Fig- 
4. At this stage it is divided into a basal portion and five movable joints, about equal in total 
length to the basal i)ortion. After the first molt the annulations become less distinct, although 
the "scale" is still cylindrical, as shown in PI. xvi. Fig. 2. The basal joint of the antenna is about 
equal in length to the "scale," undivided, and it carries upon the inner edge of its -distal extremity 
a small, short, movable joint, with a single, long, plumose hair, which is "telescoped" before the 
first moult, but fully extended afterwards. This short joint is the rudimentary antennal fla- 
gellum, which in the adult is equal in length to the entire body of the animal. 

The mandible is shown in Fig. 8. It is deeply cleft into two branches, the outer one with two 
rows of large, strongly marked dentations, and the inner one with a rudimentary palpus, two rows 
of hairs, and a finely serrated cutting edge. The first maxilla is very small, but it does not appear 
to be rudimentary. It is shown in PI. xvi, Fig. 6. No exopodite could be made out. There is 
a small endopodite, with one long, plumose hair, and two basal joints, one with two sharp cutting 
hairs and the other with one. The second maxilla is shown in PI. xvi, Fig. 7. The two basal 
joints are feebly indicated, and each carries three slender, simple hairs. The endopodite carries 
two terminal hairs, and the flat exopodite is fringed by seven. I could not determine whether 
these hairs are plumose or not. The three pairs of maxillipeds are functional and they present 
features which are characteristic of the genus Alpheus (see PI. xvi, Fig. 2). Each has a large, 
flattened, polygonal, basal joint, which carries upon its inner edge a few short, sharp teeth, and 
upon its outer edge a long, flat exopodite, with plumose swimming hairs, and an endopodite 
which presents several peculiar features. 

The endopodite of the first maxilliped is very short and two-jointed, that of the second is 
somewh.at longer and five-jointed, while that of the third is very greatly elongated, without traces 
of joints, and ending in a long, simple hair which, as shown in PI. xviii, Fig. 4, is telescoped before 
the first moult, but immediately afterwards becomes lengthened, as shown in PI. xvi, Fig. 2, untd 
it reaches forward beyond the tips of the antennules and antenuje. Following the maxillipeds are 
three pairs of buds to represent the first, second, and fifth pairs of thoracic limbs. The first bud 
consists of a single branch, which is shown by its subsequent history to be the exopodite. The 
second has two branches, a short exopodite, and an extremely short endopodite, while the third 
consists of a somewhat longer, but still rudimentary, shaft, which represents the endopodite of 
the fifth tlioracKi limb, and has no trace of an exopodite. 

The hind body is divided by joints into five abdominal somites, behind which is a long undi- 
vided region to represent the sixth abdominal somite and the telson. Before the first moult none 
of the abdominal appendages are present, but after this molt the sixth pair are faintly indicated 
under the integument of the telson, as shown in PI. xvi. Fig. 2. The telson itself is broad, sub- 
triangular, with Its posterior border nearly straight and transver.se. It carries eight pairs of stout 
plumose hairs, of which three pairs are much longer than any of the others and nearly equal. 
This set of three spines is i)laced at the angle of the posterior edge on a lobe or elongation, which, 
while it IS so slightly marked as to scarcely interrupt the triangular outline, is still very distinct 
and easily recognizable. Of the remaining five spines on each side of the middle line, one is on 
the external border, and the other four on the posterior edge between the group of three and the 
middle line. The internal one is very small and might easilj- be overlooked. 



MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 368 

THE THIRD LARVAL STAGE. 
(P\. XVI, Fix. 1-) 

After molting tlie second time the larva assumes the form shown in PI. xvi, Fig. 1. It is also 
shown, much less enlarged, in si<le view in PI. xvii, Fig. 1. The lirst and fifth thoracic limbs arc 
now functional, the second is repn^sented by a bud, all the abdominal somites are distinct, and 
the sixth abdojninal appendag(i has made its api)earance. The first five abdominal appendages 
are still unrepresented, and the endopodite of the sixth is rudimentary, although its exopodite is 
fully developed and fun(;tional. 

Those appendages which were present in stage two have undergone little ciiange. The external 
branch of the antennule has, in place of the four sense-hairs of the earlier stage, only two, which 
are much longer than before. The long terminal hair of the inner branch has lost the marginal 
hairs of the earlier stage and is now simple, while two plumose hairs have made their appearance 
on the lower surface of the distal joint of the shaft. The scale of the antenna is still cylindrical, 
but the annulatious which marked it during the earlier stage have disappeared. The flagellum 
still consists of only one shoi t Joint, and the long terminal hair which it carried at the earlier stage 
has disappeared. The mandibles, maxilla% and maxillipeds are aboat as they were before, but the 
endopodite of the third maxilliped has almost completely lost the long terminal hair of stage 
two, and has also become relatively shorter, and is now divided into four joints. 

The first thoracic leg, which was rudimentary iu stage two, has now acquired a flat basal 
joint and a plumose exopodite, like those of the preceding appendages, but the endopodite is 
represented only by a rndiinentary knob or bud upon the anterior edge of the basal joint. The 
secoTul thoracic limb is, as it was at the earlier stage, a two-lobed bud. No buds have as yet 
appeared between it and the ba.se of the fifth thoracic appendage, whi(;h is now fully developed 
and forms the most conspicuous i)eculiarity of this stage in the <leveloi>inent of Alpheus. It has 
no exopodite, its basal. joint is not enlarged nor flattened, and its long, slender, cylindrical shaft, 
made up at this stage of four joints, is jirolonged at its tip into a long, slender, tapering, simple 
hair, the eml of which reaches beyond the tips of the anteiiine when the appendage is in the posi 
tion shewn in the figure PI. XVI, Fig. 1. The api)endage .seems to have little jtower of motion ;ind 
it seldom deviates much from tlie jiosition shown in the drawing, being usually carried clo.sely 
pressed against the ventral surface of the body between the bases of the other appendages, with 
its tip directed forward. All six abdominal .^somites are distinct and movable, but the first five 
have as yet no traces of appendages. The first four. somites are short and equal, the fifth is nearly 
as long as the first four together, and the sixth is very narrow and almost twice as long as the 
fifth. The endojiodite of the sixth abdominal appendage is iiresent and of (;onsiderable size, but 
it is not as yet functional, although the exopodite, which is not very much larger, is fringed by 
six long, iilumo.se, swimming hairs and is used in locomotion. The two spines which are carried 
upon the lateral margins of the telson at an earlier stage have disai)i)eared, and there is less dif- 
ference than before in the relative sizes of the others, but the general form is the same. 

KOITRTH LARVAL STAGE. 

The subsequent history of Alpheun minor was traced l)y one of the authors at Beaufort and 
by the other at Nassau, bat as the stages which follow were found to be almost exactly like the 
corresponding stage of other species which had already be«^n drawn, it did not seem to be advisa- 
ble to make new figures, and in the remainder of the description tliti illiistrations which are 
referred to actnally represent the larvsc of other species. After its third molt the larva of 
Alpheus minor passes into its fourth stage, when it becomes almost exactly like the fourth larval 
stage of Alplirus hctcrocliclis, shown in IM. xviii, Fig. 3. There is little <haiige at the anterior end 
of the body,ex(;ept that the c-arajiace now begins to extend over the eyes, and the ears have made 
their appearance in the basal joints of the antenniiles. The mandible has lost its outer branch, 
and the basal joint of the sccoikI maxilla, PI. xvi, Fig. .'>, carries on its inner edge three hairy lobes. 
There are now five pairs of swimming appeiidag<'s in place of the three of stages one and two, and 
the four of stage three. These five are the exopodiles of the first, second, and third maxillijieds 



3f)4 MEMOmS OF THE NATIONAL ACADEMY OF SCIENCES. 

and those of the first ami second thoracic legs. The eudopodites of the maxillipeds are as before. 
The endopodite of the first thoracic leg, which was represented iu stage three by a rudimentary 
bud, now appears to be entirely wanting. The second thoracic limb, which in stage three was 
represented by a bilobed bnd, now consists of a basal joint, with a large, functional, plumose 
exopodite and a rudimentary, bud-like endopodite. Between this appendage and the base of the 
fidly developed fifth thoracic limb there is a row of buds to represent the third and fourth thoracic 
limbs, which became developed after the next molt. The fifth is about as it was in the preceding 
stage, and it carries no trace of an exopodite. The abdomen is about as before, except that the 
endo])odite of the sixth abdominal appendage, the onlj' one yet represented, is now fully devel- 
oped and fringed like the exopodite bj' long, plumose, swimming hairs. The telson has become 
elongated and narrow, and the spiues uiiou its posterior end are much smaller than before. 

THE FIFTH LARVAL STAGE. 

None of the figures of the larvje of other species exactly represent the larva of Alpheus minor 
after the next molt. The eyes are now partially covered by the carapace, and the swimming 
organs are the seven pairs of fullj" developed exopodites belonging to the three pairs of maxillipeds 
and the first four pairs of thoracic legs. At this stage these four pairs of appendages reacquire 
their endopodites, and the anterior end of the body is similar to that of the larva shown in PI. xxi, 
Fig. 1, from which, however, it differs greatly as regards the telson and the sixth abdominal ap- 
])en(l;ige. The first five abdominal appendages are now represented by buds like those shown in 
PI. XXI, Fig. 1, and in PI. xix. Figs. 1 and 2, but the terminal portion of the abdomen is nearly like 
that of Fig. 3 in PI. XX. The telson is greatly elongated, narrow, and its terminal spiues are 
very small. 

THE OLDER LARYAL STAGES OF ALPHEUS MINOR. 

During the successive molts the abdominal appendages become fully developed, the eyes be- 
come completely covered by the anterior edge of the carapace, the antennae become elongated, the 
auteniiule develops a scale, the swimming exopodTtes of the maxillipeds and thoracic legs disap- 
pear, these appendages assume their adult form, and acquire gills, and the animal gradually be- 
comes like the one shown in PI. xx. Fig. 2, which is a young Alpheus of another species. 

THE METAMORPHOSIS OF ALPHEUS HETEROCHELIS FROM THE BAHAMA ISLANDS. 

In the Bahama Islands this species passes through a series of stages which, except for a few 
minor diftereuces of detail, are exactly like those in the life history which has just been described. 

This fact is remarkable when it is known that the life history of the same species is very 
different at Beaufort, North Carolina, and that Packard has described still another life history 
for specimens of the same species which he studied at Key West. 

FIRST LARVAL STAGE. 

Tlie Bahama specimens hatch from the egg in the stage shown in side view in Fig. 1 of Pl.xviii. 
As this larva agrees iu all details of its structure with the first stage of Alpheun minor shown in 
PI. XVII, Fig. 2, already described, no further description is necessary. 

THE SECOND LARVAL STAGE. 

liike Alphens miniis the Bahama specimens of Alpheus heterochelis molt within a few hours 
after hatching, but they undergo no essential change, and PI. xvi. Fig. 2, exhibits all the essential 
characteristics, although this figure was drawu from a specimen oi Alpheus minor. 

The most noteworthy specific difference is in the relative length of the marginal spiues of the 
telson. In the first and second larval stages of both species there are eight pairs of si>ines, one 
))aii- on the outer edge and seven on the posterior edge, as shown for Alphens minor iu PI. xvi, Fig. 2, 
and for Alpheus heterochelis in PI. xvi. Fig. .3. In both s[)ecies the pair next the median line are 
rudimentarj' and the next pair very small, but the tluee which arise from the rounded angle of the 



MEMOIKS OF THE NATIONAL AOADEJfY OF SCIENCES. 365 

telaon are much more uearly equal to tlie otLers in Aliilieiis heleroclielis than in Alphenx minor. If, 
as seems probable, the triangular telsou of tlie maviuuran zoi-a is a secoudary modification of the 
deeply furcated telsou of a more ancient protozoea, then the first larval stages of Alpheus minor 
are in this respect more primitive or protozoeau than those of Alplieun heterochelis. 

THE THIRD LARVAL STAGK. 

This is shown from below in PI. xviii, Fig. 2, and a comparison with Fig. 1 of V\. x vi will show its 
very close resemblance to Alpheus minus at the same stage. The only essential ditt'erence between 
them relates to the rudimentary thoracic limbs. In both species the first thoracic limb has a 
functional swimming esopodite and a rudimentary endopodite, and in both the fifth thoracic limb 
has a greatly elongated jointed cylindrical endopodite and no cxopodite, but between these limbs 
Alpheus heterochelis has buds to represent the other three pairs of thoracic limbs, while Alpheus 
minor has buds for only one pair, and the other buds do not appear until .iftor the next molt. 

« 

THE FOUBTH LARVAL STAGE OF ALPHEUS HETEEOCHELIS. 

This is shown from below in PI. xviii, Fig. 3, and there are no noteworthy diflerences between 
it and Alpheus minor. 

THE LATER STAGES OF THE BAHAMA ALPHEUS HETEROCHELIS. 

The transformation of the larva into the adult Alpheus occupies a number of molts, and the 
general character of the changes will be understood by the study of PI. xix and xx, although 
these plates were drawn from Beaufort specimens of the species. 

THE METAMORPHOSIS OF ALPHEUS HETEROCHELIS FROM BEAUFORT, NORTH CAROLINA. 

As shown in PI. xx, Fig. 1, this, before it hatches from the egg, reaches a stage of develoj)- 
ment which somewhat resembles stages two and three of the Bahama specimens. There are many 
imiiortant ditfcreuces however, and the stage in which it hatches is not directly comparable with 
any stage in the life of the Bahama form, nor in that oi Aipheus minor. Just before hatching it 
has, like the Bahama form immediately after hatching, three pairs of fully developed swimming 
niaxilliiteds, but it also has buds to represent all five pairs of thoracic legs. The anteunary scale 
and fiagellum are much more advanced than they are irt a much later stage in the Bahama form, 
and the abdomen is much more distinctly segmented. The larva, immediately after hatching, is 
shown in side view in I'l. xix. Fig. 2, and in ventral view in Fig. 1. The antennule and antenna 
are shown on a larger sciile in Figs. 3 and 4, and the mandible and first and second maxilUe in 
Figs. 5, 0, and 7 of the same plate. The animal now has all the appendages which are present in 
the atlult, but all behind the maxillipeds are rudimentary, although they all become functional 
after the first molt, as shown in PI. xx, Fig. 3. 

The antennule, PI. xix, Fig. 3, has a long cylindrical shaft made up of three joints fringed 
with plumose hairs and terminating in an exopodite with sensory hairs and an endoj)odite or 
fiagellum, which is short and rudimentary but much longer than it is in the younger stages of the 
Bahama si)ecimens. The antenna. Fig. 4, presents even greater differences. The fiagellum is 
about as long as the scale, and two jointed, while the scale itself is flat, although its tip still pre- 
sents traces of a primitive segmented condition. It is, however, of little use in swimming, and in 
fact the larva has at this stage only very feeble locomotive power. The eyes are stalked and 
movable and almost completely uncovered. The mandible is simple and without a palpus, as 
shown in Fig. 5. The first maxilla. Fig. 6, is very small, but apparently it is not rudimentary as 
its two lobes carry cutting hairs. The second maxilla. Fig. 7, is a broad flat plate, very much 
more developed than that of the newly hatched Bahama specimen shown in PI. xvi. Fig. 5. 

The three pairs of maxillipeds (PI. xix. Fig. 1) are almost exactly like those of the newly 
hatched Bahama larva (PI. XViii, Fig. 1) or those of the Alpheus minor at the same stage (PI. xvi. 
Fig. 2), but the thoracic appendages (PI. xix. Fig. 1) are entirely difi'ereut, and the ventral surface 
of the body is covered by a mass of limbs closely crowded, all pretty well developed, but all as yet 



366 MEMOIRS OF THE NATIO^STAL ACADEMY OF SCIENCES. 

functiouless. Careful exaiuiuatioii sbows that there are five pairs (the tive pairs i>l' thoracic limbs), 
ami that all but the last pair are biramoiis. In all, the esopodites are longer than the eiiilopoilites, 
which decrease iu leugth from iu front backwards, while the eudopoditcs increase iu length. The 
later history of these limbs shows that the exopodites never become functional, as they do in the 
Bahama form. 

All six abdominal somites are distinct, although the line separating the sixth from the telson 
is faintly marked. The first five pairs of abdominal feet are represented by five biramons buds 
projecting beyond the outline of the body, while the sixth pair are oidy faintly outlined uuder the 
cuticle of the telson, which itself presents a most important difference from that of the young 
Bahama larva, as it is not triangular, but si)atulate ; and of the eight pairs of set:e the three pairs 
which in Alphcu.s minor lie on the lobe at the angle of the telson are not on a distinct lobe, nor do 
they differ iu size from the adjacent setie. 

This larva molts a few hours after hatching, and at once undergoes the most profound changes, 
and assumes the form shown ^iu PI. xx, Fig. 3. It is no longer a larva, but a young Alpheus. 
The eyes are almost covered by the carapace, the ear is well developed, and all the ajipeiidagesare 
present and functional and essentially like those of the adult. The antennule Ijas two fiagella, each 
with several joints. The tlagellum of the antenna is more than twice as long as the scale and is 
composed of twenty-two joints, while the scale has -its final form. 

The first maxilla (Fig. 5) has a large club-shaped lobe, fringed with short hairs, and a rudi- 
mentary endopodite, while the second maxilla (Fig. 6) is a broad flat plate with cutting lobes and a 
short, rod like endopodite. The three pairs of maxillipeds ( Figs. 7, 8, and 9) have assii ned the cliar- 
acteristic Macrourau form and are no longer concerned in locomotion, while the thoracic limbs have 
elongated into the five pairs of ambulatory appendages of the adult, although they still retain 
their rudimentary exo[)odites. The abdomen is now like that of the adult, and the telson (Fig. 
4) is long and narrow. An older specimen is shown in Fig. 2 and a still older one in I'l. xvii. Fig. 3. 

Comparing the history of the Bahama form with that of the North Carolina form, the most 
conspicuous peculiarity, and that which first attracts attention, is the great abbreviation of the 
latter. The Beaufort s[)ecimeus hatch in a much more advanced condition than the Bahama si)eci- 
meus, and, while the latter pass through many larval stages, the former quickly assume the adult 
form. This is not all, nor is it even the most fundamental difference between them. The develop- 
ment of the Beaufort S[)ecimens is not simi)ly accelerated; it is profoundly modified, so that nc- 
exact parallel can be drawn between any l4rval stage of the one and a slage of the other. The 
statement that the Beaufort specimens pass, before leaving the egg, through stages which are 
exhibited during the free life of the Bahama specimens would do violence to the facts; for the 
difference between them is very much more fundamental than this statement would imply. For 
example, the Bahama form has at first three, then four, then five, and then seven schizopod feet 
with functional swimming exopodites, while the Beaufort form never has more than three. As 
regards the thoracic region and the first five abdominal appendages the Beaufort larva, at the time 
of hatching (PI. xix. Fig. 1), is more advanced than the fourth larval stage of the Bahama form 
(PI. XYiii, Fig. 3), while the sixth pair of abdominal appendages are like those of the Bahama form 
at the time of hatching (PI. xvi. Fig. 3). In the Bahama form the first and fifth thoracic limbs are 
the oldest, and the others appear iu succession from in front backwards ; all five pairs make their 
appearance together in the Beaufort form. In the Bahama form the sixth pair of abdominal feet 
appear before and in the Beaufort form after the others. Many minor differences of the same 
general character show that we have to do with profound modification of the life history rather 
than with simple acceleration. 

The Development of Alpheus heterochelis from Key West. 

According to Packard's account the specimens of Alpheus heterocheUx which occur at Key West 
differ from those which occur at Beaufort in about the same way that the latter differ from those 
from tlie Bahamas, ;is the metamorphosis appears to be entirely absent iu the Key West speci- 
mens. Packard states that, while still inside the egg, they had all the appendages of the adult 
in essentially the adult form. There were five pairs of thoracic legs and the first pair had large 



MEMOIRS OF THE NATIONAL ACADEMY OF SOIENCES. 367 

cheliP, and the eyes were nearly sessile. In tLis case also tliere seems to be modification as well as 
acceleration, as Packard says tbat there were only live pairs of abdominal t'eiit and tbat these were 
well developed. It may seem to some that the fact that these three forms present such great and 
constant difl'erenccs in development is a reason for regarding them as three distinct species, but, 
whether we hold that they belong to one, two, or three species, they will still furnish proof of the 
existence of profound moditicatious in the life histories of adults which have reuuiiued almost 
exactly alike. 

Careful and minute comparison between atlult specimeus from Beaufort and Nassau showed 
the closest agreement in nearly all particulars (v. Cliai>. v, I't. First, Section ii), and it has there- 
fore seemed best for us to regard them as belonging to 4 single species; the more so since our 
discovery that diflerent individuals of another species found at Nassau {Alpheun Hmdcyi) difler from 
one another during their larval stages in somewhat the same way that the Beaufort specimens of 
heterochelis dit!er from the Bahama specimens. 

Alpheun minor and Alpheus heterochelis are very distiuct species. The adults have diverged 
from one another so far that one coulil not possibly be mistaken for the other ; yet the life history of 
the Bahama heterochelis is so exactly like that of Alpheus minor, both at Beaufort and in the 
Bahamas, that the same figures of the early stages will serve for both ; for the larval stages of 
heterochelis have undergone local modifications, while the adults have remaiued almost absolutely 
uuchauged, except as regards the reproductive elements and their product. 

Section V. — Larval development op Alpheus saulcyi. 

An egg of Alpheus saulcyi jast ready to hatch is shown in PI. xxi, Fig. 5. The large claws are 
plainly visible through the transparent shell. The auteunic are folded back alongside the body, 
while the abdominal and closely packed thoracic appendages are directed forward. The telson 
overlaps the head. 

First larra (length,^ i^^o inch). — Fig. 1 shows the larva as it is just hatched. It belongs to 
the variety found in the brown sponges. The various parts may be seen more highly magnified in 
PI. XXI, Figs.l, C, 7,!), and PI. xxii. Figs. 1-8, 12. In both varieties the animal hatched as a scliizo- 
pod, loosely infolded in a larval skin, but not invariablj', as I have noticed that in one or two caseH, 
where females of the longicarpus with very few, perhaps half a dozen eggs, produced young, th6 
metamorphosis was completely lost, the larvie being in a stage corresponding to that usually at- 
tained after the second molt and represented in PI. xxi. Fig. 8 This is referred to again at 
the end of the section. 

To return to the first larva (PI. xxi, Fig. 1) ; this is fifteen one-hundredths of an inch long. It 
is semi-transparent and colorless, except for spots of characteristic red and yellow pigment sprinkled 
freely on the abdomen, the telson, and appendages. Kudimentary gills are present and a remnailt 
of unab.sorbed green yolk is conspicuous in the stomach. The carai)ace covers the bases of all the 
thoracic appendages but the last pair. It is produced forward into a short simple spine, the ros- 
trum, which extends between the eyes. There is a rudiment, on either side, of the ocidar spines 
(PI. XXII, Fig. G), which soon grow forward and give to the front the characteristic trident shape. 
The eyes project forward, only the extreme base of the stalk being covered by the carai)ace. A 
median eye or ocellus is present just below and between the bases of the lateral eye stalks. 

Both pairs of antenn<e are biramous and jointed. The auteuuules (Fig. 8) ccmsist of a stout 
peduncle, a short endopodite, and a shorter bud or outer branch, which bears several bunches of 
sensory filaments. The peduncle is composed of three segments, as in the adult; the basal joint 
being four times the length of either of the other two, and bearing on its outer side a rudimentary 
aural scale. The upper margin of each joint carries one or more plumose hairs. The antenuic 
(PI. XXII, Fig. 7) are formed on the adult plan. There is an inner antennal stalk consisting of 
two joints, bearing a rudimentary flagellum, and an outer scale or exopodite. The distal margin 
of the exopodite is garnished with plumose hairs and carries a short outer spur. 

The mandibles (Fig. 12, drawn from a larva after the first moult) are deeply cleft, as in the adult. 
The outer branch is dentated at its distal end and carries a pali)us. The first maxiihe (Fig. G, 



368 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

shown with more detail in Fig. 3, Pi. xxii) have adult characters. They are bira:n<>ns. The endo- 
podite is stout and toothed at its apex. The more slender outer division bears a short spine 
near the distal end. In the second masill.e (Fis- ti, PI. xxi) the scaphoguathite or respiratory 
plate is most prominent. This is now composed of an anterior portion, bordered with from six to 
twelve long plumose hairs and a posterior, rudimentary, and hairless lobe. The inner division 
(endopodite) has the adult form, while the innermost lobes of the adult appendage (PI. XXIV. Fig. 
9) are unrepresented. 

The maxillipeds are all biramous appendages, and their exopodites are the principal swim- 
ming organs. The endopodite of the first pair is short and stout and divided at its tii). That of 
the third pair is three-jointed and equaj in length to the exoi>odite. In the first pair of thoracic 
legs (PI. XXI, Figs. -1 and 7) the inecpiality of the chehe is very marked, and, as we have alrea'ly 
seen, it is so for some time before hatching. Individuals differ somewhat in this respect. The 
articulations of the carpus and meros are distinct. The exopodites of this and of the three suc- 
ceeding pairs of thoracic limbs ai'e tii)ped witli rudimentary iiivaginated hairs. The second pair of 
pereiopods (PI. xxii, Fig. 1) are chelate, but the articulations of the carpus are not distinct. The 
third iiair of pereiopods (Fig. 2) end in 'bidentated dactyles and have short exopodites. The 
fifth pair are without swimming organs. 

All the abdominal appendages are present and functional, excepting the sixth pair. They 
have only very short hairs nntil after the tirst moult. The first pair (PI. xxii, Fig. 5) consist 
of a larger outer and smaller inner blade. This endopodite remains rudimentary in the adult 
male, but nearly equals the exopodite in length in the female, as will be seen by reference to PI. 
XXIV, Figs. -1 and 5. This convenient sexual mark probably appears early, but can not be relied 
upon at this stage. The second (PI. xxii, Fig. 4) and three succeeding pairs of pleopods have a 
stout base, an t)uter blade like that of the first pair, and a shorter endoiwdite which bears on its 
inner margin a lobule or palp. The sixth pair, or uropods (PI. xxi, Fig. 'J), are not yet free. Tiie 
inner and smaller divisions point forward, meeting on the middle line. The telson, which termi- 
nates the body, covering the outer uropodal limbs, is a rounded, spatulate plate, with a median UDtcii. 
Its free posterior edge is fringed with seven pairs of plumose spines, the tirst or median pair being 
rudimentary, and the next four succeeding pairs long and nearly etpial. 
• Second larva (length, ^0% inch). — The first moult takes place either immediately or very soon 
after hatching. The animal as it now appears is shown in PI. xxi. Fig. 2. The principal external 
changes thus produced are the following: (1) The rostrum and ocular arciies extend farther over 
the eyes. (2) Both divisions of the antennules are considerably extended. The fiagella of the 
antenme are from three to four times tlieir former size and are articulated into twenty to thirty 
rings, the scale still not jiassiug the peduncle. {■>) The thoracic api)endages have more of the 
adult characteristics. The articulations of the carpus of the second pair are distinct. The exo- 
podites of the first four pairs are functional, and the last i)air has grown forward. (4) The 
pleopods presently acquire swimming hairs; the telson plate is free and the uropods are func- 
tional for the tirst time. (5) The last thoracic segment is still uncovered and the eyes are 
incompletely hooded. 

Tliird larva (length, about ^ inch). — The tliird larva as it appears after the second moult, 
which takes place in twenty-five to thirty hours after hatching, is represented in PI. xxi. Fig. 
8. It has now the general adult character, and can not be called a larva in the strict sense. At 
even this early age the pugnacious instinct is strong, and although only about one-sixth of an 
inch long, it snaps audibly the fingers of its large ''hand,'' which is carried extended forward. It 
also swims on the bottom of the jar in all resi)ects like the adult. Only a few globules of yolk 
remain in the stomach. The gills are now quite prominent. They are evidently functional to 
some degree, and were so, possibly, at an earlier date. The yellow and red pigment cells have 
nearly all disappeared or are temporarily withdrawn from view. 

A most jjrominent change at the second moult is the extension forward of the rostrum and 
the ocular spines, which form a hood over each eye. The autennal peduncle surpasses the scale, 
and its ttagellum nearly equals the carapace in length. As in the adult, the large chelie are very 
l)roininent. The exopodites of the thoracic a[)pendages have dwindled to rudiments. The view 
of the head of a four-days old Alpheus is shown in Fig. 3, PI. XXi. 



MEMOIKS OF TOE NATIONAL ACADEMY OF SCIENCES. 369 

The fourth form (after tliird moult). — When six or seven day-s old the third moult is passed, 
but only slight changes are introduced. The small chela ami the inner and outer antenme of this 
phase are given in Figs. 9, 10, 16, PI. xxil. The inner branch of the antennules is still relatively 
short; the basal or aural si)ine extends to nearly the end of the tirst joint. The bristle-bordered 
plate of the antenuai has now develoi)ed a considerable spine near its outer extremity, a rudiment 
of which appears in the tirst larva (Fig. 7). This represents the squanial spine, to which the [ilate 
is ordinarily attached, in the a<lnlt. The spine is here developeil from the plate. The latter iiTay 
disapiiear, as we shall see further on, to be finally regenerated from the base of the spine. The 
small chela has the adult form. 

'I'he fifth form (after fourth moult). — These animjvls moulted the fourth time ten days after 
hatching. Very liltle change was apparent, except in size, and beyond this point we did not follow 
them. 

METAMOKPnOSlS OF ALPHKHS SATILCYl FirRTHER AHBRKVIATED. 

As was stated above, tiic metaiiiorpiiosis of Alphiux xautcyi may be still further accelerated 
80 as to practically disappear altogether. This fact is illustrated by a young Alpheus hatched 
in a glass dish Ai)ril L'.'i (Fig. 17, PI. XXII). The prawn (var. longicar2}us) was taken, from a brown 
sponge. The eggs, half a dozen in luimber, were slow in developing. The small chela is shown 
in Fig. 15. 

This phase corresponds with that usually attiuned after the second moult (shown in Fig. 8, 
PI. XXI), with which it corresponds in size, and color. All the thoracic and abdominal appendages 
have nearly the adul.t foi'in, the exoiiodites of the former being rudimentary, as in Fig. 8. The 
large chela is most i>rominent, being nearly as large again as the smaller one. The eyes are partly 
hooded, but not so much as the four-day old jirawn represented by Fig. 3. The Alpheus had to be 
held in a compressorium in order to be drawn, so that the parts are slightly distorted by pressure. 
At the time of hatching most of the hairs on the appendages generally are in a rudimentary 
condition. 

S. Mis. 94 ^4 



V. 

ALPHEUS: A STUDY IN THE DEVELOPMENT OF CRUSTACEA. 



By Francis H. Hereick. 



CONTENTS. 



III. 

IV. 

V. 

VI. 



Introduction. 
Methods. 
Part First : 

I. The habits and color variations of Alpbeiis. 
II. Variations in Alpheus heteroclielis. 

The abbreviated development of Alpheus and its 

relation to the environment. 
The adult. 

Variations from the specific type. 
Measurements. 
VII. The causes and significance of variation in Al- 
pheus satilcyi. 
Part Second : 

I. Structure of the first liirva of Alpheus saulci/i. 
II. The origin of ovarian eggs in Alpheus, Homarus, 
and Palinurus. 
III. Segmentation in 4l2)heus minus. 
IV. The development of Alpheus. 

First slaye: Segmentation to formation of blas- 
toderm. 
Second stage: Migration of cells from blastoderm 

to the interior. The invaginatlou-stage. 
Third singe: Optic disks and ventral plate. 
Fourth stage: Thickening of optic disks. Ru- 
diments of appendages. 
Fifth stage: Rudiments of three pairu of ap- 
pendages. Optic disks closely united by 
transverse cord. Degenerative changes. 
Sixth stage: The egg-uauplius. 
Seventh stage: Seven jiairs of appendages 
formed. 

[With thirty 



Part Second— Continued. 

IV. The development of Alpheus — Continued. 

Eighth stage: Nine pairs of appendages present. 

Ninth stage: Eye-2)igment formed. 

Tenth stage: Ganglia of ventral nerve-cord 

distinct and comi)letely separated from the 

skin. 
Eleventh stage: Embryo about to hatch {Al- 

pheus heterochelis). 
Twelfth stage: First larva {Alpheus saulcyi). 
Thirteenth stage: Young Alpheus, four to ten 

days old. 

V. Notes on the Segmentation of Crustacea. 
VI. Cell Degeneration. 

VII. The Origin aud History of Wandering Cells in 
Alpheus. 
VIII. The Development of the Nervous System. 
IX. The Eyes. 

The median eye of the larva and adult. 
General anatomy of the eye-stalk. 
Structure of the ommatidium. 
Arrangement of the ouiniatidia. 
The development of the compound eye. 

(1) Origin of the optic disk. 

(2) Development of the retina and the 

optic ganglion. 
The eye underthe influence of light and dark- 
ness. 
X. Summary of Part Second. 
XI. References. 

Explanation of figures (accompanying each plate), 
•eight plates.] 



INTRODUCTION. 

The observations ofifered in tbis memoir were uudertaljen at Beaufort, Nortb Carolina, in 
June, 1885, at the Marine Zoological Station of the Johns Uopkins University. But little was 
accomplished, however, until the next and following seasons, 1886-87, when I enjoyed the advan- 
tages of tbis laboratory in the Bahama Islands. 

A part of this memoir was accepted as a thesis for the degree of Ph. D. by the Board of 
University Studies of the Johns Hopkins University in May, 1888. 

I take this opportunity of thanking Professor Brooks for his invaluable counsel, aid, aud 
encouragement from the beginning to the end of the work. 

At Nassau, New Providence, during a sojourn of four months (March to July, 1887), I had the 
rare opportunity of a making a comparative study of a large number of Crustacea. At least thir- 
teen species of Alpheus were discovered on the coral reefs and shores of New Pro%'idence, and 
in all these the eggs have been obtained, aud in nearly all the larvte or first zocas have been hatched 
in aquaria. Many of these forms are new or but little known, and when the means of publication 
is found it is hoped that their comparative and systematic zoology can be fully illustrated. 

370 



MEMOIRS OF TOE ^JATIONAL ACADEMY OF SCIENCES. 371 

The majority of the ilecap(»(l (Jnustawii have a Um>^ and coni|>licatc.tl metamorphosis. That 
ill a few forms the early stajjes are jiimpeil, so tiiac the yoiiiij; hatch in pnicticaily the adult coudi- 
tion, is a remarkable fa(!t,'aiid the discovery of a probable cause for this phenomenon in ^pbeus 
is one of the most interestin<,' results of that part of our work which deals with the metamorphosis 
of the genus. 

The development of Alpheus has never, I believe, been previously studied, excepting the 
metamorphosis of the two I'.eanfort species, so that there is no work of others to refer to, which 
bears directly upon our subject. I!ut tiie literature of the Arthroiiods is very great, comujensurate 
indeed with the size of the group. During the |>roges8 of this work a number of imi)ortant papers 
have appeared which are referred to either in I he text or in n«)tes. While much is known of tbe 
Arthropods as a whole and of that large division of them included under the Crustacea, it is 
probably true that a great deal of tliis knowledge is of a very fragmentary and unsatisfactory 
nature. There is great need for detailetl and full accounts of the dev»',lopment and organogeny 
of many forms in order that the relations of the various members of the Arthropod type may be 
clearly established. 

The present work may be regarded as a contribution toward sup[)lyiug the need just men- 
tioned, but how imperfectly it is unnecessary to say. 

The plan of making observations ufioii other Crustacea for comparison with the more detailed 
studies of Ali)heus has been as yet only partially carried out. The early stages of ISlcnopus hispiduH, 
Homariis Americanus, and Pontonia domeatica have, however, been followed, and less completely 
those of Hippa talpoides and PaUtmonetes vith/drii,: 

Spence Bate (3) states that the shortened development of Alpheus was first described in bis 
memoir, with drawings, communicated to the Royal Society in 187C, from a specimen procured in 
the Mauritius, lie named his s|)eciinen Ilomarnlpheus, ''from the impression that species producing 
a Megalopa could not be placed in same genus as those producing a Zoea." He says: "The orig 
inal of my drawing is 2""" in length and was i)rocured from a specimen 14"""' long, resembling the 
figure that I have given oi Alpheus minvn, Say. An iusi)ectiou of this drawing (3, PI. oxxii. Fig. 1 ) 
leaves some doultt as to whether there was not an error in referring this form to the genus. The 
general shape is unlike that of Al[)heu8, the abdomen being three times as long as the carapace, 
and there appear to be only three pairs of thoracic appeiulages behind the chelipeds. 

I'ackard (40) in 18SI was the first to describe a shortened metamorphosis for Alpheus hetcrochelis. 
In some brief notes ])ublislied in the American Naturalist of that year, he states that both this and 
the small green Alpheus (yl.»ji«H.s) occur in abundance at Key West, Florida, in theexcurrent open- 
ings of large sponges. This fact is interesting, and i>robably significant also, as will be later 
shown. Packard descril)es tlie first larva of this Florida form as much further advanced toward 
the adult state than is the first zoea of the Beaufort species, according to the observations of 
Brooks. In fact it more nearly agrees with the first larva of a Bahamau Ali)beus soon to be described, 
in which the metamorphosis is nearly lost. 'The Nassau t'orin of Alpheus hcterochelis has, as I have 
recently ascertained, a eomplete metamorphosis. The bearings of these facts will be discussed 
further on. 

The larval development of the Beaufort Alphei was studied by Brooks (7) and a short 
abstract of his results was published in 1882. This is all, I believe, that has been [jreviously done 
on the embryology of these Crustacea. Several abstracts of the present work appeared in 1887-'88 
(20-22). 

METHODS OF WORK. 

Several species of prawns, such as Stcnopus and Pontonia, repeatedly laid eggs while kept in 
aquaria, and doubtless I should have succeeded equally well with Alpheus, if sufficient pains had 
been taken. As it was, only two or three individuals gratified me in this respect, but in each case 
the ova failed to develop. The animals were therefore taken from the sea with eggs in the earliest 
pha?fes of develoi)ment, and were kept under observation in an aquarium for the length of time 
required. The ova were then carefully removed from the pIeopods,aiid were hardened at intervals of 
thirty minutes or one hour or a longer time, according to the phase or age of the eml>ryo. By obtain- 
ing i^number of series in this way the whole life history within the egg could bo followed, and by 



372 MEMOmS OF THE NATIONAL ACADEMY OF SCIENCESo 

this means I was able to observe the peculiar movements of the wandering cells and the formation of 
germ-layers, which are often very difficult to interpret, when we rely upon material taken by chance. 

Experience with the use of Perenyi's fluid in preparing the eggs led me to discard this reagent 
altogether, and to substitute for it Kleiueuberg's picro-sulphuric acid, made up either with water 
or 30 per cent alcohol. The alcoholic solution works equally well and economizes time. The Pe- 
renyi is too violent and uneven in its action. While it serves fairly well in some cases, it generally 
swells out the membranes or shell by the .rapid endosmosis, and distorts some part of the egg or 
embryo in consequence. The egg is frequently deformed and the shell ruptured. The ova should 
be transferred directly from the killiug fluid to 70 per cent alcohol, and they will then generally 
retain their normal shape, and can thence be removed to alcohol of a higher grade for permanent 
keeping. If, however, they are carried from the Kleineuberg fluid to a weaker alcohol (30 per 
cent), distortion is sure to follow, the capsule bursting and the egg sometimes exploding. 

Preparations of the entire embryo as well as sections were made, but very little was attempted 
with the living egg. For surface preparations the hardened ova were first i)unctured to allow 
the fluid to penetrate the shell more easily and they were then stained entire, in Kleinenberg's 
hamiotoxylon. They were afterwards shelled, when this was possible ; saturated with paraffin by 
the turpentine-paraffin method, and were then mounted. While the paraffin was congealing they 
were carefully placed in position with a hand lens. This last inii)ortant and often troublesome 
process was rendered easy by the differential property of the stain, which alfects only the embry- 
oiiic cells, leaving the ylok, which in preserved eggs is of a light straw coloi-, unaltered. The 
embryonic tissues are thus made to api)ear nearly black on a light background. The embryo was 
then cut away from the rest of the egg by the microtome razor ; attached to the slide by collodion 
and mounted in balsam; or the egg was cut in two and both halves were similarly treated. All 
drawings which represent surface views excepting Fig. 10 were made from objects thus prepared. 

In general, Kleinenberg's hiemotoxylon proved to be the best staining fluid, and it is especially 
useful in this case, where the massive yolk contains numerous elements, the relations of which it is 
important to determine. The carmines are less serviceable, since the food yolk is also afl'ected by 
them. Soda carmines (Beccari's formula) proves to be incapable of removing pigment from the 
eyes, although it is specially recommended for this purpose. This may be easily efl'ected by soak- 
ing the entire tissues in very weak solutions of nitric acid for a considerable length of time. Gaule's 
quadruple stain of hremotoxylon, eosiu, safl'rauiu, and nigrosin was also tried with excellent results, 
but this method is very laborious, and since our inquiries do not extend in most cases, to cell 
structure it is unueccessary.* 

Perenyi's fluid is sometimes available for swelling the chorion and thus aiding in its removal, 
although the embryo is liable to injury. It is also helpful in studying the egg with low powers. 
The food yolk, which is often dark green, is aflected less actively by this reagent than the embry- 
onic tissue. The latter is turned to a waxy whiteness and is thus clearly defined for a short time, 
but the yolk is soon decolorized unless the eggs are transferred to water, becoming pink, and finally 
light yellow after preservation in alcohol. 

Paet First. 

, i. — the habits and color variation of alpheus. 

Some facts of general interest have been gathered from a study of the Alpheus in its natural 
environment on the coral shores and reefs of the Bahamas, and in giving these we will limit our- 
selves mainly to the three S[)ecies which have contributed the material for the history of the em- 
bryo, viz : Alpheus minus Say, from Beaufort, N. C, A. heterochelis Say, from Beaufort, N. C, 
and Nassau, New Providence, and A. sanlcyi, from Nassau, New Providence. The genus 
Alpheus comprises numerous species spread over a large part of the globe, many of which are 
closely connected by intermediate forms. From North America upwards of twenty species of 
Alpheus have been described; five are known to inhabit the eastern coast of the United States, 
three from Florida, and two others {A. minus and A. heterochelis), which range from Panama to as 

* In studying the development of the lobster, which has also a large egg, I have found it necessary to adojit new 
uifthiMls, especially in the treatment of the eggs for surface preparations. In most cases, the egg-membranes are best 
removed by the aid of hot water. 



MEMOIRS OK THE NATIONAL ACADEMY OF SCIENCES. 373 

far north as Virginia. From Florida and Cuba nine species are recordeil. I have found twelve 
species of this prolili(; jjcniis, or altout one -half the nmnher described for the whole American con- 
tiueut, inhabiting the beautiful little reef of growing coral called Oix Point to the eastward of 
Nassau Harbor and along the margins of the little bay which was just in front of our laboratory. 
Another species (.1. irchsteri Kingsley), first reported from Florida, was also discovered on Green 
Key reef, a few miles from Nassau. 

From collections which I made at Abaco and Andros Islands. I am led to believe that the 
different species are quite g<nierally distributed in the liahamas, and as these islands have prob- 
ably been largely populated from the South, we may expect tiie same forms to occur at Cuba and 
at other West Indian Islands. This genus, howcs'er widely distributed, is essentially tropical and 
abounds in all coral seas. Of the great family of the Crustacea which make their home on the 
submergeil reefs of growing coral, Alpheus is perhaps the most proM)ineiit and thoroughly charac- 
teristic. They pop out of almost every rock which is brought up from the bottom, and everj- loose 
head or block of growing coral, with its clusters of alga", sponge, and sea fans, which you pull 
from the reef, resounds with the click of their little hammers. •^ 

Some of these auimals lead a semi-parasitic life in sponges, or seclude themselves in the ])orou8 
limestone which forms the solid lloor of the beach, and others, again, live under loose shells and 
stones in the white coral sand. Some are highly and beautifully colored, and with few exceptions 
the pigment is characteristic; of the species for any locality. In all cases the claws of the first 
pair of walking legs are enormously enlarged and serve as formidable weapons of defen.se so re- 
markable in this genus, and in most there is the greatest disparity in the size of these claws one 
either the right or left, being the larger. One species, the habits of whi(!h are peculiar, carries 
the larger of these claws so folded under the body as to be completely concealed. It can, however 
quickly withdraw this weapon and make a rapid thrust when an enemy comes near.* By the scis- 
sor like blades of the large claws a sharp metallic rejioit is produced. This is true of nearly all the 
species, and so abundant arc many in these islands that a constant fusilade is kept up along some 
of the shores at low tide. This snapi)ing jiropensity is shared by both sexes whether in or out of 
the water, and it is undoubtedly correlated with their pugimcious habits, [f two males or females 
of the same or different species are i)laced in the same aquarium, they will dismember each other 
in a very short time, and one is usually literally torn to pieces. 

The sounds emitted by Alpheus Jictcrochclis are the loudest I have heard from any meml)er of 
this genus. We fre<pu'ntly kept this species in glass dishes in our room for several days at a time 
and sharp reports like the explosion of a small torpedo or pop gun were heard at intervals through 
the day and night. It sometinu's swims with its large claw so widely opened as to suggest dislo- 
cation. This weaj)on then reminds one of a cocked jjistol, and the report ai)parently follows in 
the same way that the click follows the impact of the hammer on the lock. 1 have given this 
mattter no closer attention, but find that Mr. Wood-Mason, who is quoted in a notice on " Stridulatiu"- 
Crustacea" t in "Nature," (05) has ofl'ered anoth(>r explanation. According to this observ<'r the 
sound always accompanies a sudden oi)ening of the elaws to their fullest extent, and may be caused 
either by impact of the dactyle upon the joint to which it is articulated or "by forcible withdrawal 
of the huge .stopper-like tooth of the dactylopodite from its pit in the immovable arm in the claw." 
It seems most probable to me that the sound is caused l)y impact, and most likely by the rapid 
closure of the finger into its socket. | 



* This sppcii'H is ontirely new. TIip large conooiilod claw suggests a poison apparatus. Tlio " fingers " aj»es.- 
ceediugly slender and sharp at the points. Although kept for over a week in an .aqii.ariiini it emitted no sonnds. 

♦ According to Wood-Ma.son sonnd-prodncing organs in Crnsfacea were first hronght to notice by Iliigenilorf, in 
V. dcr Decker's "Roiscn in Ost-Africa (Crnstaccen)," and were afterwards observed hy liiinself in liis dredgin" ex- 
pedition to tlie Andaman I.slands. The stridnlating organs— scr.ipers and rasps — may be either ou the carapace and 
appendages or on the appendages alone. 

! Hotli Kent and Wood-Mason speak of the soiinds emitted by the Alphei as if prodnced by the extension or 
opening of the claw. As pointed ont above, it is jnst tlio other way, the sonn<l following upon the imp.act of dactvle 
and [iiopodns, when the tooth of the dactyle is not pnlled out of its socket but driven into it. None of the coiulitions 
of piston movement are present. The walls .and floor of the pit are relatively soft, while the tips of the elaw are 
dense and stony. The "click" can be .artificially produced when the claws are clamped with rubber, whether the 
"stopper " is present or not. 



374 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

In AlplienH heterochelis the dactyle of the large pincers is a curred blade which shuts down 
into a groove on the occludeiit margin of the " thumb," and closes over the latter like a pair of 
shears. The huge stopper like tooth is borne on the inner and proximal edge of the dactylopodite 
and fits neatly into a corre.s])onding pit in the " thumb," in line with the groove just mentioned. 
The object of this plug is evidently to steady the movable dactyle and to prevent lateral strain 
and the dislocation which might result, and thus to give it a strong grip on any object which it 
has seized. In alcoholic specimens in which the relations of the parts are well preserved the stop- 
per works freely in and out the well, and not like a " tightly packed piston from a cylinder closed 
at one end." 

(The claw is widely opened, before the sound is produced, but the sound is not prodnced while 
the claw is open, but at the instant when it is violently and suddenly closed. It is due to the 
impact of the "thumb" and "finger," and I have frequently seen specimens of A. heterochelis, 
when i)repared for combat, facing each other for several seconds with claws distended to the 
utmost. In these cases the " snap" does not come until the claw is closed. In fighting the 
claw is not used as a clasper, but as a saber. The sharp external edge is a weapon of such eflQciency 
that I have seen individuals killed and almost cut in two by a single blow. — W. K. B.) 

A large brown sponge, Hircinia arcuta, which is not to be mistaken, grows on the shallow 
reefs and off the shores of all the Bahama Islands which 1 visited. It is found from just below 
low tide mark out to one-half a fathom or more of water, where its great size and sooty brown color 
distinguish it at once on the white bottom. These "loggerheads "are round and much flattened (the 
smaller ones more vase-shaped), and of a coriaceous texture; they sometimes measure li feet in 
diameter. There is commonly one, sometimes two, large exhalent chimneys into which small fish, 
young spring lobsters, and other Crustacea, often beat a hasty retreat. It is easily broken open since 
it has no consistent skeleton. If a sponge colony of this kind is pulled and torn apart, one is certain 
to find it swarming and crackling with a small species of Alpheus, which quarter themselves in 
the intricately winding pores of the sponge. The sounds emitted from every fragment of these 
mutilated sponges remind one forcibly of " those made when sparks are taken by the nuckles from 
the prime conductor of a small electrical machine," as Wood-Mason remarks. Hundreds of indi- 
viduals may be collected from a single large si)ecimen. 

These animals have an average length of about 12™'". They are nearly colorless, excepting 
the large cheliiB, which are tipped with brown, reddish orange, or bright blue. The females are so 
swollen with their eggs or burdened with the weight of those attached to the abdomen that they 
can crawl only with great difiBculty, if taken from the water. The eggs are few in number and of 
unusually large size, their diameter varying from one-twenty-second inch to one-twenty fifth inch, 
and their number from six to twenty. Tiiese are most conimonly yellow, but may be either bright 
green, olive, greenish white, brown, brownish yellow, or dull white. The ova and ovarian eggs 
have always the same tint in the same individual. Although translucent and apparently colorless, 
upon close inspecition the body is seen to be sprinkled with cells of reddish and yellow pigment. 

Anotlier quite different sponge grows on all the reefs in from one to two fnthoms or more of 
water. There are se%'eral varieties ot this, which may be told by their olive green color, yellow 
flesh, and clumpy, irregular shape, as well as by the putrescent mucous which some of them ponr 
out when broken open. In about nine out often of these sponges one will fiinl a single pair of 
Alpheus (rarely more than this), which resemble those living in the brown sponge, but differ from 
them in several important points. We are concerned at the present with the color variations only. 
They iire distinguished by their large size (averaging about 23""" in h-iigth) and uniform color. 
The females exceed the males greatly in l»ulk, owing to the large size and number of their eggs. 
In both sexes the hirge claws are bright red (v. PI. iv, and for details section iv). 

The female is practically inert during the breeding season, and at such times is well juotected 
in her sponge or against any green surface by the bright green ovaries which fill tlie whole upper 
part of the body and by the mass of similarly colored eggs attached to the abdomen below. Only 
two pairs, or four individuals, out of a hundred or more which were examined showed any variation 
from these colors. In these the eggs were yellow, and the i)igment on the claws was more orange 
than red. The table which follows shows the variations between two large females taken, respec- 
tively, from the brown and green sponges, and between the size, number, and color of the eggs. 



MEMOIRS OF TOE NATIONAL ACADEMY OV SCIENCES. 



375 



HftblUt of Alphens. 


Length of $ . 


Mamber of 


OlameUr. 


Color. 


Color of adult. 1 


Brown sponge. . . 
Gre«u sponge 


Inches, 
i 

lA- 


19 
347 


Inches, 


Yellow (variable) 

Usually green ; in 
tbis case yellow. 


Large chel.TP.roil (blue 
or hrowu iu otburs.) 

Large cheliu, orange- 
red. 



These two forms, altliough apparently distiuct. are seen, however, by closer study to belong to 
the same species; but besides the more sui)erficial variations just mentioned, there are others of a 
more remarkable character, the morphological significance of which is considered in sections IV 
and V. 

Of this species, Alpheiix .snulcyi, Guerin, it is necessary, for descrii)tive purposes, to distin- 
guish two varieties, viz : 

Alpheus sanlcyl, variet3' longicarpus (from brown sponges), 
Alphens mulcyi, variety brcricarpus (from green sponges). 

These two varieties shade completely into each other by numerons intermediate forms. The 
longicarpxift varies greatly iu size and in the color of the body and eggs (besides the other more 
profouud variations mentioned in section v), while the brevicarpxig type from the green spouges is 
more uniform in size and stable in color and other characters. The former variety is well pro- 
tected from outside enemies while in the tortuous mazes of its sponge, as its great numbers would 
show, if any evidence under this head were needed. The enemies which invade them successfully 
seem to be parasites.* 

Possibly the variety inhabiting the green sponge does require color-i>rotection, especially since 
the females are very inert during the breeding season. They are, indeed, admirably protected 
when exposed on the green surface of sponges, alga;, etc. The bright color on the tips of the large 
claws, which only are protruded from the i)laces of concealment, recall the similarly colored heads 
of boring annelids, which abound on the reef, but this fact may have no significance. 

It seems (juitc probable that if we have in this Alphens a case of protective coloring, it is due 
very largely to individual adaptibility. This view implies great individual plasticity, which does 
not appear in any of the species of Alphens known to me within a restricted area. 

The colors of certain Crustacea, and also the colors of their eggs, are known to vary greatly 
with the surroundings. Iu the Alphens, parasitic in the brown sponges, these colors vary cousid- 
eraldy where the surrounding conditions are the same. However, the color of the ovarian eggs is 
always the same as that of those already laid, and, although these animals were kept for several 
days at a time in difiereutly colored dishes, I never observed any very marked change in the color 
of the ovary, but these experiments were not continued long enough or carefully enough to be con- 
clusive. The eggs of Alphens hetfrochclis are almost invariably of a dull olive color, while, as in 
the case of the parasite of the green spouge, about one in a hundred has bright yellow eggs. In 
the first case at least this may possibly be an instance of reversion to one of the original colors 
from which the green was selected. In most species of Alpheus the color of the eggs is fixed and 
uniform for any locality, and, as already suggested, may have a protective significance; but iu a 
few other cases, where this is not true, the color is not only variable in different individuals, but 
probably also in the same individual. 

Alphens heterochelis from Beaufort, N. C, is uniformly of a dark olive-green color, with some 
red and blue on the api)endages. It lives iu the beds of oyster shells, which are more or less 



* A parasitic Isopoil, probably a Bnpyrus, is foand on both tlie varieties, bnt is ijiost common with the dweller in 
the brown sponge. It appears aa a tumid buncb, firmly rooted in tUo br.ancliial cavity or to the under side of the 
abdomen. In this connection I will mention another curions par.osite which was found infesting the eggs of a single 
female taken from a brown spouge at Abaco. This is a large, s])lierir:il, nnicellnlar organism in the encysteil state. 
The egg, with the embryo, is p.icked full of them. (v. Fig. I'.Ut and section IV, Part Second.) 

In looking over .a collection of unpublished ilrawings of Crust.acea, ni.ide by the associates of Louis Agassiz and 
deposited iu the library of the Museum of Comparalivi- Zoology of Ilarvaril College, I find a sketch (by H. J. Clark, 
December 23, 18,">7) of a Bopijrus taken from the branchial cavity of Aljiheus heterochelis. 



376 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

exposed at low tide. Alpheus vilnus has a similar environment and is similarly colored. Alpheus 
heterochelis from Nassau, New Providence, on the other hand, lives under loose stones, amid the 
white coral sands of the beach, and is noticeably transparent, looking as if the color had been 
ble<ached out of it. The body is sprinkled with dots of brown pigment. The claws and legs are 
pale greenish. Young and old are invariably colored alike. 

In a collection of adult Alpheus of either sex of the same or of several species, where there is 
a difference in size of the large claws, it is noticed that either the right or the left, indifferently, 
may be the greater. As we will see, this differentiation of the chehe begins in one instance before 
the animal is hatched. Is this right and left handed condition to be explained by inheritance 
from the parents ? In about forty larvai of a small brood of Alpheun saulcyi, all invariably had the 
left claw eidargcd, and in a smaller number (all that were preserved), from another female of the 
same species, the left chela was also in each case the larger. This would indicate that the young 
of the same mother have always the same claw, either right or left, the greater, and that this phe- 
nomenon is one of direct heredity from the parents. But to prove this it is only necessary to trace 
right and left handed broods to parents which are themselves right and left handed, respectively. 
This, unfortunately, I have not done, as my attention was not called to the subject while at the 
seashore.* 

The breeding season of Alphens begins at Beaufort, N. C, about April 1. It covered the 
period of our staj- at Nassau (March to July), and ])robal>ly Ix^gau earlier and lasted considerably 
later.! There the temx^erature is high and remarkably constant, the annual range being about 15° 
(temperature of air 70° F. in March, 80° in June), and in conseuuence the early phases of devel- 
opment are rapidly passed. Not one prawn in a hundred was found with eggs in an earlier stage 
than that of yolk segmentation. 

II. — VARIATIONS IN ALPHEUS HETEROCHELIS. 

A renewed comparison of AlpheuK heterochdis with the Nassau form lends support to the con- 
clusion already reached that we here have to do with two varieties of the same species. There are 
certain diflerences, which systematic zoologists might regard as of specific value, but they are no 
greater than we have proved to exist among individuals of the same si>ecies living in the same 
sponge, (v. Section V.) 

The Nassau specimens average smaller, but the chief ditlerence lies in the shape of the small 
chela. The propodus of this appendage in the Nassau form is relatively shorter and thicker in 
both sexes. Both tiugers are nearly cylindrical, and covered with hairs, which are distributed 
either singly or in tufts. In the Beaufort heterochelis there is a striking variation in the small 
chela which appears to have escaped detection. Judging from the small collection at my command 
it is a .sexual variation. In the females the small chela is like tliat of the Nassau form, but is 
usually longer and .slenderer. The dactyle is about one-half the length of the propodus. In 
the males the dactyle is relatively much shorter, and has a median longitudinal carina which is 
continued into the apex of the claw. In transverse section the dactyle is trihedral, with two con- 
cave sides, corresponding to the deep groove on either side of the keel. These grooves are fringed 
with a row of stout plumose .setie. Similar rows of set;e occur on the sides of the o[)posing 
" thumb." 

Perhaps the most interesting variation wliich I have observed in the Beaufort heterochelis has 
reference to the size of the egg. The eggs in this locality have an average diameter ot about one 



" Mr. J. J. Northrop, of Coliiinbia College, while at Nassau iu the winter and sprinj; of 1890, kindly oflered to 
collect for me some specimens o( Alpheus saiihyi with young. Ou February 10 be coIbMited six females, five from greeu 
sponges, one of which h.a(l a brood of sixteen young, and one sratill female with three larv.-e from the " loggerhead" 
sponge. In the first instance the left chela w.as the largest in the mother anA iu each of the sixteen young. In the 
latter, two h,ad the right claw enlarged and one the left. The inference is snggested that when the claw of the same 
side is iuvariaWy the greater in all the young, this character is doubly inherited from both father and mother, but the 
data are insulficient to settle this point. 

t Professor H. V. Wilson found this species breeding around Greeu Turtle Key from July until December. Mr. 
Northrop found newly hatched you ug early in February. It therefore breeds the year through, which is probably 
true of many of the Crustacea. 



MEMOIRS OP THE NATIONAL ACADEMY OF SCIENCES. 377 

twenty-fourth inch, but two females were found which carried a few bunches of very small eggs, nor- 
mally <ilu('d to tJio anterior swiinnieretvS. These eggs measured only one tifty-third to one sixty-Hfth 
inch in diameter, that is, the contents of the smaller was about one-twelfth that of the larger egg. 
This occasional production of very small eggs exhibits a tendency, which is still present in 
the species of this locality to-day, to revert to its old metamori)hosis long since laid aside. 

III.— THE ABBREVIATED DEVELOPMENT OF ALPHEUS AND ITS RELATION TO T/lE ENVIRONMENT. 

Related species, as a rule, resemble each other more in their early stages of derelopment than 
in their adult state. This is not, however, invariably true, since all animals, whether young or 
adult, must adapt themselves to their environment or be destroyed. It is probable that animals 
in all stages of growth are equally plastic and tend to vary with the varying conditions of life. 

The early life in large classes of the animal kingdom, as fishes, birds, and manjinals, is si)ent 
either in the protecting membranes of the egg or within the body of the i)arent, and is thus but 
slightly affected by external conditions, and suffers little change in consequence. In other groups, 
on the contrary, and in the Crustacea in particular, the case is very different. Uere the young 
are usually hatched in a very immature condition, and lead a life of their own at the surface of 
the ocean, wholly independent of their parents. They have accordingly adapted them.selves to this 
mode of life, and the variations thus entailed have led to the production of the zoi^a, a locomotor 
larva, fundamentally different from the adult. We may regard the zol-a as a secondary, adaptive 
form, directly descended from an ancestral protozoi-aii type. After passing a longer or shorter 
period (usually of several weeks) at the surface of the sea, the adult state is gradually reached 
through a comi>licated series of changes, and the animal adapts itself to new conditions on the sea 
bottom or on the shore. 

Now, if the habits of the adult and larva should tend to converge, if the adults should adapt 
them-selves to an entirely new environment, which it is necessary for the young to become fitted 
for at once as soon as hatched, we would expect that the zoi-al stages, formally assume<l to bridge 
over a gap which no longer exists, would be dropped or shifted to the egg. This seems to have 
actually taken place, and is illustrated in a remarkable manner in the genus Alpheus. 

Most of the species, which are very numerous, inhabit the shores, in common with many 
related forms, and, as already stated, they abound on coral reefs. They all, as a rule, lialcli as 
zoiia-like and have a complicated metunioridiosis. Two species have been discovered, however, 
which have adopted a parasitic life, and in ea(;li the larval period is accelerated. In one, which is 
.semiparasitic, the metamorphosis is partially abbreviated; in the other, which is completely para- 
sitic, the metamorphosis is completely lost. Still more interesting and significant is the fact that 
one of the species in one locality is nonparanitic and has a complicated metamorphosis, while the same 
species from another locality is itarasitic and has the metamorphosis abridged. 

We will now cou.sider more particularly the history of these two forms, in order to make a 
clearer comparison. The species are — 

t Alpheus heterochelis, from Nassau, New Providence. 

(1) ? Alpheus heterochelis, from Keaufort, North Caraliua. 
( Alpheus heterochelis, from Key West, Florida. 

(2) Alpheus saulcyi, from Nassau, New Providence. 

ALPHEUS HKTEROCHELI3 FROM THE BAHAMAS. 

This species, found at Nassau, exemplifies the development commcm to the genus, as .seen, for 
instance, in A. normani (Kingsley), which is closely associated with it, A. minus Say, and in many 
other Bahaman forms. It is one of the common species at Dix Point, and may be found in abun- 
dance on the shore of the little bay, in pools left by the ebb tide, under shells or loose fragments 
of coral. 

First larva (length = i inch). — The three pairs of maxillijteds, each with long exopodites ending 
in feathered hairs, are the principal loi^omotor organs. Two pairs of riidiinentarv thoracic legs 
are present. All the abdominal segments, but none of their appendages, are formed. 



378 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

The antennules consist of a stoat jointed stalk, the terminal segment of which bears four 
sensory filaments.\ A long plumose spine springs from the extremity of the second joint on the 
inner side. 

Tlie antennte are biramous, the two branches arising apparently out of a common basal segment. 
The outer division is a scale-like plate. It bears on its extreme inner border a row of i)lumose hairs, 
eight to ten in number. The endopodite is slender and shorter than the scale. It terminates in a ■ 
short spine or defaticle, from near the base of which springs a long plumose hair. The eyes are 
large and uncovered. The mandible is simple. 

The telson is a broad triangular plate, the terminal side of which is garnished with the charac- 
teristic zocal spines, the number, relative size, and position of which vary slightly in the different 
species. There are in this case eight pairs of these spinfes. The first or median pair is rudimen- 
tary; the secoud is not half the length of the third. The lateral angles of the plate are each 
prolonged into a short lobe, bearing three spines. There is no marked median notch, but there is 
a slight median depression. The rudiments of the sixth pair of abdominal ajipendages are plainly 
seen. 

Second larva. — With the first molt the endopodites of the maxillipeds lengthen. Three pairs 
of rudimentary pereiopods are now present, the last of which are the longest. Of the pleopods 
only the sixth pair are represented, whether free or not was not observed. 

ALFBEUS HETEROCHELIS FROM BEAUFORT. 

The peculiar metamorphosis of the Beaufort Heterochelis was described in 1884 by Brooks, who 
also showed that in this respect it departs widely from the associated Alpheua mmus. 

The form in question is hatched as a larva with preparations for the schizopod stage. It has the 
usual swimming organs, but all the thoracic legs are present in the condition of rudimentary buds. 
Tiie abdominal segments are formed, and the buds of the first five paiis of feet belonging to them. 
The eyes are not completely covered by the carapace. At the first molt the rudiments of the 
sixth pair of abdominal feet are added, and the larva undergoes profound changes. All the ap- 
pendages are now functional and the eyes are nearly hooded. With later molts the adult char- 
acters become more pronounced, but the marked difference of the great claws appears only after 
several months. 

ALPHEUS HETEROCHELIS FROM FLORIDA. 

The short description, given by Packard in 1881, of the first larval stage of this species from 
Key West, where it inhabits sponges, has already been alluded to. From this we infer that the 
development is considerably more abridged than in the Beaufort case. This is also indicated by his 
figure of one of the abdominal appendages. He says : The eyes are nearly sessile, the yolk nearly 
absorbed, although the embryo (in the egg) was near the time of liatching. The antennse are " well 
developed." All the thoracic legs are present, their joints distinct, " the first pair about twice 
as thick as the others, the claws rather large, but not so disproportionately so as in the adult form, 
but as much so as in the larva in the second stage of the lobster. Abdomen broad and fiat, spatu- 
late at the end, much as in the adult. There were five pairs of abdominal feet or swimmerets, each 
with endopodite and exopodite, like those of the second larval stage of the lobster." 

ALPHEUS SAULCYI FROM THE BAHAMAS. 

In this form, the metamorphosis of which is fully described in another paper, we have either 
an abridged development in which the general adult ch.aracters, very marked in the first larva, 
are all acquired in twenty four lionrs after hatching, or a case where the short metamorphosis is 
done away with entirely, so that the animal leaves the egg in the full adult form. 

Comparing the histories just given with the one before us, we find that the first larva of 
AlphcHs sauleyi is about equivalent to the third larva of the Heterochelis from Beaufort, and rather 
more advanced than the first larva of this species from Florida. 

Tlie eggs of the Alphei, with the development unabridged, are invariably small and quite 
numerous. In the two species, however, with .shortened metamorphosis, the ova are fewer and many 
times larger. Moreover, as would be expected, the degree of abbreviation is correlated with the 



MEMOIRS OF TOE NATFONAI. ACADEMY OF SCIENCES. 



370 



size and miinbcr of the eggs. These and the other facts which we have been considerin.^ are 
given in tabular view below: 



Spoclea. 


Habits. 


Metamorpbosifl. 


Number 
of enes. 


Diameter 
of egg. 


Lengtii of 
I'emole. 


Alpheiis minus (from Ucanfort). 
A. Iieterocholis (fmni Nass.aii) . .. 
A. hoterncliclis (from Heuiifort) . 
A. heteroclicliM (from Klonda) .. 
A. saiileyi (var. Un-vircarpiis) ... 
A. saulcyi (var. loiigicarpus) 


Nnii-parasitic 

do 


Complete 

do 


•r.oo 

300-500 
liVO-SOO 


Inch. 


Inehf. 
i-l 

l-U 

1-li 


.-..do 


Abridged 

. do 


Complotoly parasitic. 
do 


Nearly lost 

Cotnpletoly absent 
(in some cases). 


100-3.50 
5-20 


.'.4 


i-n 

i-i 





* Nnmber not accurately d.eterniined. 

The eggs of Alpheus are usually spherical when freshly laid, but they change their shape, 
becoming more elongate in course of development and increase somewhat in size.* The eggs of 
A. saulcyi are usually oblong. They vary from one twenty-eighth to one twenty-third of an inch, 
taking the mean of the long and short diameters. The extreme limits of the uumber of eggs vary 
somewhat from the numhers given above, which are the average limits. 

In the genus Alpheus we thus have several stages in the abbreviation of the metamorphosis 
between the macronran zoi-a stage and the adult form. What is the cause of this gradual sujjpres- 
sion of the zoea like form ? Tlie conclusion seems to be unavoidable that in the Bahaman species 
this shortened life of the larva is directly related to the conditions of life. As the adults of the 
species in question became more and more dependent upon a semiparasitict mode of life, it would 
be clearly beneficial to reduce the larval period, in order that tlie young might be hatched titte(i to 
live in an environment similar to that of the adults. It the zoi'-a brood were swei)t out to sea by the 
tides, and were to spend several weeks in the larval condition at the surface of the ocean, the 
chances for large numbers to find particular sponges along the shores, when the adult state was 
reached, would be greatly lessened, it is likely that the larva' of this Alpheus are never carried far 
from the shores, but while they undoubtedly leave the sponge in which they are born, they prob- 
ably establish themselves very soon in a new one. (The young remain a short time after hatching, 
attached to the swimmerets of the mother.) 

This supposition is strengthened by what we know of the peculiar history of Alpheus heterochelis. 
The Nassau heterochelis probably never changed its adult habits or adopted a parasitic mode of life ; 
consecpieutly it has retained undisturbed its complex larval development. The Floridian form has 
become a i)arasite, and its metamorphosis is accelerated as the result. From this the JSeaiifort 
Alpheus with its less abridged development has doubtless been derived (the species extending north- 
ward from the (lulf of Mexico), and it is within the po.ssible, at least, to suppose that in this form 
the metamorphosis, once lost by parasitism, is now being rei'stablished. 

No fewer than three species of macroura, together with the Alpheus above described, occur in 
the largo brown sponges (llirchiia arcnia) of the Haliama islands. These (one of which is also an 
Alpheus) live in the larger osculii, are less regular in their o(!Currence, and evidently have not 
adopted a stationary parasitic life. In none of them is the metamorphosis of the larva abbreviated. 
Alpheus minus is also reported as occurring in the large exhalent openings of s]>onges at Key West, 
but in this ca.se we do not know, first, whether this is a fixed or only a transient habit, and 
secon<lly, we know nothing of its metamorphosis under tlie.se conditions. 

Thus while in Ali)lieus the abbreviated metamorphosis may bo exjilained as an .adaptation 
to a parasitic mode of life, the «|uestion is probably often complicated by conditions which are not 
ea.sy to determine. There is a general tendency among the higher Ibrnis of certain group.s, as in 
the Cephalopods among the Mollusca, to reach the adult conditions rapidly by omitting some of 
the early embryonic stages. 



• An egg of J. Haulciji var. longicarput, just ready to hatch (PI. xxi, Pig. 5), measares jju by rfhi inch. 
t The Alplu'i which iuh.abit spon^fs are commeuNals rather than par.iMlte.s in the strict sense. They derive pro- 
tection from the spoujjo colony, and receive the benefit of the circulutiug currents of water which are set np within it. 



380 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

An abridged larval developmeut Las been attributed to tlie following uiacroura : The lobster 
Homarns americanus ; the crayfishes; Hippolyte polaris ; Pakemoneies varians; Pala'inon potiuna; Pa- 
Iwmon aflspersus and Eriphia spinifronH (as first observed by Ratbke, according to Packard) ; Bytho- 
earis lexicopsis (observed by G. O. Sars, according to S. I. Smith) ; Alpheus heterochelis, and A. naiilciii. 
To this list we mnst probably add the names of many deep-sea decapoda, Munidopsis, Glypho- 
crangon, Elasmonotus inermis, Sabinea princeps, Acanthephyra gracilis, and Pn.siphai'' princeps, as 
inferred by S. I. Smith, on account of the extraordinarily large size of their eggs. An egg of 
remarkable dimensions is that of " the little shrimp [Parapasiphad sulcatifrons,) which carries only 
fifteen to twenty eggs, each of which is more than 4 millimeters iu diameter, and approximately 
equal to a hundredth of the bulk of the animal i)rodiicing it — a case in which the egg is relatively 
nearly as large as iu many birds! " "Although the great size of the eggs," says Prof. Smith, " is 
Iiighly characteristic of many deep-water species, it is by no means characteristic of all, and the 
size of the eggs has no definite relation to' the bathymetrical habitat, and is often very different iu 
closely allied species, even where both are inhabitants of deep water (59)." 

The larval life of both terrestrial and fresh- water Crustacea is generally sliort as compared 
with that of marine forms, and the case of the crayfish m.iy fijid an explanation iu the well-known 
law that fresh-water life tends to shorten the development, as is shown in a remarkable manner in 
the fresh-water variety of Palwmoiietes varians, described by Boas (4). Why, on the other hand, 
it is beneficial for the lobster to abbreviate its larval development is not plain, since its young at 
the present time hatch apparently under the same conditions as other pelagic larva*, and, like 
them, swim at the surface of the ocean. S. I. Smith (58) and Kyder (55) have given accounts of 
the larval history of the lobster. (Since this paper was written I have undertaken a revision of 
this subject, and the results will be given iu a fully illustrated report to the United States Com- 
missioner of Fish and Fisheries.) While this animal hatches in a precocious state its life at the sur- 
face is by no means short, since, according to Eyder, it ordinarily requires seven weeks to pass 
through six molts. The first larva hatches in a schizopod stage, but there are no abdominal legs 
and the antennse are somewhat rudimentary. The first ecdysis, according to Ryder, does not occur 
until from three to six days after hatching.* It is in the second stage that the second to fifth 
pairs of abdominal appendages make their appearance. 

The third stage is preceded by a molt ten to fifteen days after hatching, and now the append- 
ages of the last abdominal .segment are formed. After the fourtii molt (fifth stage) the young 
lobster, now 14"""' long, quite closely resembles the adult. It swims more on the bottom. The 
flagella of the antennai are equal to the cephalo-thorax in length. The exopodites of the thoracic 
legs are reduced to bare rudiments. The chelipeds .show adult characters. The first pair of swim- 
raerets are develoijed in the seventh stage, at the end of which there is a decided difference between 
the great claws. 

It will be seen that the fifth stage in Ryder's account, attained at the end of the third week, 
nearly corresiionds with the third larva oi Alpheus saulcyi (Fig. 8, PI. xxi) as it appears twenty-four 
hours after hatching, but the latter has the more decided adult characters. The young Alpheus 
is further advanced than the lobster at the time of hatching and reaches maturity in a remark- 
ably shorter period. 

Boas calls attention to the fact that while the young of the salt and fresh water forms of 
Palwmonetes varians are very different, the adults of these two varieties resemble each other very 
closely. Much more remarkable is the case ot' Alpheus heterochelis, even if we regard the Nassau 
form as a distinct species, and that of Alpheus saulcyi, where we have the same species living iu 
the same sponge, hatching now as a larva and now as a form possessed of all the external adult 
<:haracters. 

Both the long and short metamorphosis has been attributed to the West Indian shore cralt 
Gegarcinus. This highly colored crab {Oegarcinus ruricola) is very almndant at Nassau, and from 
its exceptionally large egg we may safely infer that the development has here been shortened. 
Fritz Miiller (42) has found abbreviated development in the South American crabs, Triclmdactylus 
and ^J/^/Zfirt ("mountain crab"). 

* A delicate moulted skin, whicl] is easily overlooked, either comes oflfwith tbe egg moiubranes at the time of 
hatching or is shed shortly after, as my own observations have clearly shown. 



MEMOIRS OF THK NATIONAL ACADEMY OF SCIENCES. 381 

The habits of the lieniiit ciivbs, tlioii}j;h secondarily aequireil in comparatively recent times, 
have had no tendency to shorten the larval period. This is also true ot the Pinnotheres. Simi- 
larly the commeiisalisni of such forms as I'ontonia domcstica, which lives in the mantle cavity of 
.several species of Piuua, has in uo way affected its development. 

IV THE ADULT. 

The Alpheus whose development has just been traced was provisionally named Alphem prce- 
cox(li2), in allusion to its greatly accelerated metamorphosis. It has since been found to agree iu 
most particulars with the description and tigure of Alpheus sauhi/i given by Guoriu in Kanioii de 
la Sagra's History of Cuba (IS), la Gucrin's drawings the long spine (s(iuamal spine) of the 
antenna* is represented as continuous throughout its length with the scale, and the carpus of the 
second pair of thoracic legs as divided into three segments. The segmentation of the car[)us of this 
ai»i)eudage is one of the most constant of si)ecific characters. If these figures are accurately 
drawn, the two forms iu (juestion are certainly not specifically identical ; but though not at first able 
to satisfy myself ou this point, or to decide from the short and imperfect description, it seemed 
best after further study to adopt Outirin's name. 

The systematic zoology of the genus Ali)lieus is in a very unsatisfactory state, and in the 
absence of adequate and well executed drawings, and too often with only vague or general descriit- 
tions, the attempt to ideuiify the less known species is apt to be attended with most doubtful 
success. 

It is now necessary to complete the account of the metamorphosis of this Alpheus by giving 
a description of the adult form. The Alpheus saulcyi resideut in certain green sponges found on 
the Bahama reefs is regarded as the typical form of this species. 

DIAGNOSIS. 

Carapace ends anteriorly in three spines. The median spine or rostrum inclined, especially in the 
female ; arises from the edges of the carapace, like the lateral or orbital spiues ; barely surpasses the latter 
iu length : writhout keel. Body and appendages generally smooth ; large chela slightly twisted, smooth, no 
transverse constrictions ; small chela subcylindrical, short ; dactyle nearly straight, slender, one-half as long 
as propoilus: carpus of this appendage short. Aural spine of inner antenna variable in length ; rarely sur- 
passes the middle of the second segment. Basal segment of outer antenna is produced into an outer, inferior 
spine, and an upper rudimentary spur ; articulated with it is a squamal spine, ou which is developed a con- 
spicuous scale. Carpus of second pair of thoracic legs superficially segmented into five parts. 

SPECIAL DESCRIPTION. 

Length : Smallest found in green sponges, 9.5""", S ; largest, 42""", 9 ; average length, 25 to 
30""". Females exceed the males a little iu length, and greatly surpass the latter in size when 
swollen with their eggs. 

Color: The color of this form is shown iu PI. iv. Large claw vermillion above, fading out 
towards proximal half, and nearly colorless below. On upper face of claw a transverse colorless 
band is often seen. Small chela often tinged with red, also the terminal segment of the third pair 
of niaxillipeds. Body, pale, translucent, with scattered cells of reddish or yellow pigmeut, subject 
to (piantitative variation, and visible to the naked eye on close inspection or by aid of a lens. 

A young male which was kept for several days in an aquarium molted and lost completely the 
bright color of its claws. Sexes are colored alike, excepting the eggs and ovaries of the female, 
which are bright green. 

In one or two instances a pair of these Crustacea were found which exhibited a variation from 
these tints. In these cases the male and female were of light-reddish orange and the claws deep 
orange red, darkest on the '• fingers" ; eggs and ovaries of female golden yellow. Length of 9 , 33""". 
Number of eggs attached to abdomen, 347. The male in this case also, after a moult, was apparently 
colorless, contrary to the lule that upon molting the (-olors are enhanced. 

. The carapace is smooth, translucent, and, like the abdomen, takes on more or less the hue of 
the yellow or green ovaries. It ends anteriorly in a trident, formed by the median rostrum and 



382 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

ocular spines. The rostrum is short, subacute, broader at base than loug, feebly convex aoove, 
without crest. The orbital spines are separated from the rostrum by a shallow superlicial groove, 
and the marginal notch on each side has a regular V/shaped outline. Length of siiines and width 
of notch are slightly variable. 

The lateral compression of caiapax is not marked. Frontal angle (angle made by middle line 
above and below rostrum, greater in 9 than in S . In some females with the carapace bulged out 
by the ovaries the angle is as great as 45°. In males without conspicuous "forehead'' frontal 
angle, 10°. 

The telson ends bluntly. It is two-thirds as broad as long, and twice as broad at base as at 
apex. There is a single pair of short spines at the posterior extremity on either side the middle 
line, and two (or more) separate spines upon either side further forward. There is a wide and 
shallow^ median dei)ression. 

The compound eye§ are conspicuous, owing to their dark pigment and the transparency of the 
carapace, and in the largest adults they show no traces of degeneracy. There is a i^ermanent 
ocelluii [P]. XXII, Fig. 18), which occupies the same position and has the same characters as at birth. 
It consists of a pigmented body embedded in a short median papilla, situated below the compound 
eyes and between the bases of the antennules. 

The antennules (Fig. 4, PI. xxiii) consist of a three-jointed stem or protopodite, an exopodite, 
and endopodite. The first segment of the stem is largest and bears an external spine (aural spine), 
which protects the auditory sac. The latter is large and conspicuous Jn this genus. It usually 
contains some pigment cells and grains of sand. Second segment about half as long as first; 
third, four-fifths as long as second. Endopodite one and one-half times the length of stalk, slender. 
Exopodite compound, a slender flagellum branching from near the end of the stouter proximal 
portion. On the uiKler side of the latter the sensory filaments (olfactory seta") are borne, distrib- 
uted in seven to ten bunches of two to three in a bunch. 

The antenna; (Fig. 8, PI. xxiii) are composed of three parts — a basal portion (protopodite), 
which carries a squamous spine (exopodite), and on its inner and lower side a long three-jointed 
stem, whii h bears a flagellum (endopodite). 

The protopodite consists of a proximal segment (coxopodite) and a larger distal one (basipo- 
dite). A prominent papilliform process is seen on the inner side of the coxopodite at its point of 
junction with the basipodite. Upon it the duct of the green gland probably opens to the exterior. 
The basipodite is continued into a prominent spine below and into one or more rudimentary sjiurs 
above. To it is articulated a long, stout, scale-bearing spine. The scale plate, usually shorter 
than the spine and attached to it for less than half its length, is fringed on its inner free edge with 
idumose setic. The antennal stem or peduncle consists of two short i)roximal segments and a loug 
distal one, which carries the multarticulate flagellum. The latter is often hairy, and is two to 
three times the length of the peduncle. The relative lengths of the different parts for an average 
specimen is shown in Fig. 8, PI, xxm, and in PI. iv. 

The mandibles (Fig. 3, PI. xxiii) are strongly bifurcate, as is characteristic of the genus. The 
larger division is finely tuberculated, while the masticatory surface of the slenderer branch is 
raised into sharp teeth. This bears a jointed palp (endopodite) on the inner side. The mandibular 
palpus is short; its terminal segment large and hairy. 

The first maxilla (PI. xxiv, Fig. 7) consists of three divisions — a smaller branch (endopodite), 
a larger branch (basipodite), divided at the apex and terminated by several long spines, and a 
larger spatula-shaped fork, the maxillary surface of which is beset with spines (coxopodite). (v. 
Description of figure.) 

The second maxilla (PI. xxiv, Fig. 9) is composed of three portions. (1) The long respiratory 
plate; the "bailer" or scaphoguathite, fringed with a row of setae. (2) An outer and lobulatcd 
division (coxopodite and basipodite), the inner edge of which are closely set with bristles, and (3) 
a median rudimentary endopodite. 

The first pair of maxillipeds (Fig. 7, PI. xxiii) are made up of a long, strap-shaped exopodite, 
with jointed sette at the extremity and a small setigerous plate at its base; a small, two-jointed 
endopodite, protopodite, aud epipodite. The protopodite is divided by a fissure into two lobes, a 
larger (basipodite), with dense rows of bristles on its maxillary surface, and a smaller division 
(ci)X(ipodite). The epipodite is an oblong plate, united by a short stalk to the protopodite. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 383 

The second pair of iiiaxillipod.s iVi};. (J) lias a loiij;, strap-sbajicd exopodite, like tbat of the 
first pair. The eiidoi)odite is iuourved, aud segmented into at least four parts. The dactylopo- 
dite or terminal segment is the longest, aud is thickly studded with serrate bristles and set»;. 
There is a small oval epipodite. 

The third i)air of niaxillipeds (Fig. 5) consist of a basal piece (coxopodite) and a long two- 
branched appendage. The large branch consists of three distinct segments— a long proximal one 
(basipodite (?) and iscliioi>odite), a shorter one (meropodite), and a long terminal segment (carpo- 
jHtdite, propodite, and dactyloi)odite). The exopodite springs from the base of the first segnjeut, 
and is about equal to it in length. The lower surface of the two terminal. joints is covered by 
numerous transverse I'ows of serrated bristles, and the cndof this appendage is armed with several 
spines. 

The first pair of pereiopods or walking legs bear the great cliekp ("hands'' or "shears"). 
The cheliie are very uuetjual. Large claw (relatively larger in $ ) smooth, slightly twisted; outer 
aud ui)per border sometimes marked by a linear crest; several spurs or tuberosities near the 
articular surface of the dactylc; dactyle shaped like end of pruning knife, its concave inner 
margin and tooth-like point shutting into a groove of the opposing "thumb." This groove of the 
jtropodus is continuous with the well, in which the stopper-like tooth of the dactyle fits. It is 
bounded by a rectangular process above and a less prominent one below. Tips of lingers barely 
overlapping. Dactyle sometimes overreaches propodus. Thumb (or extremity of proi»odus from 
joint of dactyle) one-third to one-half length ''palmer portion "of propodus. Dactyle works some- 
what obliquely. Tips of fingers simple. Propodus sometimes hooked. 

Small claw (Fig. 3, PI. xxiv) usually carried bent downward. Fingers nearly equal; three- 
fourths as long as palmer portion of hand; bent slightly downward and outward; propodus sub- 
cylindrical; half as broad as long; tip simple or slightly bifid. Small Imnches of seta- on fingers. 

Second pair of pereiopods (Fig. 1, PI. xxiii): The characters of this appendage appear to 
be remarkably constant and of considerable specific value. They end in a small claw, the 
liiigws of which are provided with bunches of long hairs. Carpus superficially constricted into 
live rings or segments. First or j)roximal segment nearly equal to 2+3+4+5. Second, third, 
and fourth of nearly equal length; fifth equals 2+3. 

The third, fourth (Fig. 2, VI. xxiii), and fifth pairs (Fig. 1, PI. xxrv) of walking legs are similar 
to each other, the fifth pair beiug shortest. Each ends in a short, horny dactyle which is bifid at 
apex, the primary claw bearing a smaller secondary tooth at base. Pro])odus little shorter than 
meros in the fifth i)air, and carries numerous bunches of short set;e on its under side. There are 
also fouud iu this region of the propodus four to six stout appressed spurs. 

The first jiair of pleopods is specially ditfeicutiated in the sexes, and forms one of the most 
convenient marks of distinction. The first abdominal limb of the male is shown in Fig. 4, PI. 
XXIV, and the corresponding appendage of the female in Fig. 5, and the typical appendage in Fig. 
U. In the unmodified limb the protopodite carries as usual the two branches — eudopodite aud 
exopodite — each fringed with long seta-. The endopodite is a little longer than its fellow and 
bears a rudimentary secondary branch, which springs from near the middle of its inner edge. 
In the male (Fig. 4) the appendage is considerably reduced. Tlw exopodite is short and the 
inner branch a small rudimeut. In the female (Fig. o) the modiflcatiou has not proceeded so far. 
The endopodite is here the shorter and has no secondary branch. In the very young forms 
(first larva) these apjiendages appear to be nearly alike in both sexes (PI. xxii, Fig. 5). 

The uropods or sixth pair of pleopods hardly require si)ecial notice (PI. iv). The endopodite, 
much the smaller division, is an oval plate, and on its upper side there is a roughened median 
ridge. The free edges of the plates are fringed with long and chisely set plumose setiu. 

V. — VAKIATIONS FROM TUE SPECIFIC TYPE. 

We are now ready to consider the remarkable variations which this species undergoes. The 
form just describtd was taken as typical, and the largest adults invariably belong to it. 

(1) Variety Longimrpvs: This is the widest departure from the first form or type aud is very 
commonly met with in the brown sponges already noticed. Probably more than 90 per cent of the 



384 MEMOIES OF THE NATIONAL AOADEMY OF SCIENCES. 

individuals found iu them beloug to this variety. The color variations of this form have already 
been giveu iu section i. 

The rostrum is sometimes wanting, as iu the individual from which Fig. 11, PI. xxii, was 
drawu. This variation has been noticed iu other species and is interesting, siuce the absence of 
the rostrum is a constant character in a closely related series of forms, which are placed by Dana 
in a separate geuus (Betwus). These variatious indicate that the uniform presence or absence of a 
rostrum is a specific aud not a generic character, as has already been shown by Iviugsley (29). 
The structural poiuts of diflereuce between the loiKjicarpus and the other form lie chietly iu the 
antennae and first pair of walking legs. These may be seen by a comparison of Figs. 11, 13, 18, 
PI. XXII, and Fig. L', PI. xxiv, with Figs. 4, 8, PI. xxiii, aud Fig. 3, PI. xxiv. 

In the first pair of auteun:e the aural spine (Fig. 11, PI. xxii) is scarcely more than half the 
length of the first segment of the stem. It is blunt aud somewhat ovate iu shape, as seeu from 
above. 

(2) In the other form (var. brevicarpus) the aural spine (Fig. 4, PI. xxiii) has a dittereut shape, 
and is relatively uearly twice as long. In this case it extends beyond the first segmeut to two- 
thirds the leugth of the second. The secoud or outer auteuua of the lonywirpnn is armed with two 
spines at its base (Fig. 11, PI. xxii) ; an inferior and outer basal spiue, and a sligiitly longer one, 
the squamous spine, articulated to the joint carryiug the latter. There is uo scale. The basal s[)iue 
is rather more than one-half the leugth of the antenual stalk. There may be present a small 
tubercle on the upper surface of the segment beariug the basal spine, near the articulation. 

In variety hreviearpvs (Fig. S, PI. xxiii) the squamous spuie is stout aud reaches nearly to the 
end of the antenual stalk. There also spriugs from its inner and proximal margin an elongate 
plate or scale, the inner free edge of which is fringed with plumose setre; scale not quite as long 
as spiue. The inferior basal spine not one-half the length of the squamous spiue. There is a rounded 
or pointed tubercle over basal spine near the joint. 

The small chela of the first pair of thoracic legs of the lougicarjms (Fig. 2, PI. xxiv) is short 
and broad. The finger ends in two or three horny teeth or prongs, which interlock those of the 
opposing thumb. The dactyle bears on its outer surface a tuft of peculiar hairs. The latter are 
finely serrate and have beut or hooked tips. The carpus is relatively very long, quite as long as 
the palmar portion of the propodus. 

In the breriearpus the small chela is long aud somewhat narrower (Fig. 3, PI. xxiv). Tips 
of fingers usually simple, but sometimes notched; the peculiar tuft of hairs is wanting. Carpus 
relatively short ; about one-third the length of the palm. 

The large chela of the longicarpus may also difler noticeably from the brevicarpus type. (Com- 
pare Fig. M, PI. XXIV with the figures on PI. iv.) Fig. 8 represents a common form of this append- 
age. The propodus is long, cylindrical, slightly twisted, very smooth, and polished; ends above 
dactyle in a short spine aud below iu a rudimentary thumb with claw-like tip. Dactyle overreaches 
proijodus, and its inner margin is not concave, or but slightly so. 

These two forms, difleriug in the particulars just mentioned, would doubtless be considered 
as two distinct species if only these facts were known. A prolonged study, however, of a large 
number of individuals, collected both iu sponges and from porous rocks on a number of reefs, has 
i-esulted iu the discovery of a complete series of intermediate links. These conuecting forms sug- 
gest a number of important questions relating to the causes and significance of variation. 

By far the greater number of individuals of this species have the characteristics of the two 
varieties just described, but about five per cent of the collection made at diflereut points near Nassau 
present intermediate characters.* 

More fully stated, the noticeable points of variation are as follows: (1) The relative length of 
the autenuular stalk and aural spine; (2) the lengths of the antenual spines relative to each 
other and to the peduncle of the antenna; the presence or absence of a squame or scale; (3) 
the character of the dactyle and propodus of the small chela of the first pair of pereiopods ; (4) 
the length of the carpus of the small cheliped; (5) the general shape and character of the large 

* While the species live, as a rale, in the interior of the green aud brown sponges, a few undersized individuals 
may be found, by careful searching, among the loose blocks of porous coral which are scattered over the reef, and it 
frequently happens that these iudividualt possess intermediate characters between the two varieties just described. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



385 



claw. (1) With resjuTl to tlu' (irst point, wi- unci witli ;i i)erteotly };iii'lui'ff<l series between I lie 
two extremes (FIks. 1 1, 18, I'I. xxii, Fisfs. 4, IM. xxiii). (2) The same is tine of the relative lengths 
of the antennal spines, the seale, and peduncle (Figs. 11, 13, 14, PI. xxil). In Fig. 11 there is no 
evident scale and the spines are nearly equal. In Fig. 14 the spines are markedly unequal, and 
there is a nidiinentary scale. In Fig. l.'J this .scale is further developed. (.S) Grca* variation is seen 
iu the small chela. The liiigeis of this claw may each end in two or three prongs, or one in two, 
the other in three, or the tii>s of the fingers may he simi)le or merely notched. The tuft of jiecnliar 
seta' on the dactyle may be reduced or wanting. (4) Various stages between the long and short 
carpus are observed, and (.">) slight variations not easily described are constantly seen iu the relative 
size, shape, and other characters of the large chela. 

These variations are shown in a general way in Table 1. (For detailed measurement, v. Table 
II.) The fifteen ca.ses here recorded were selected from upward of seventy-five, in a large number 
of which the variable parts were drawn for more careful comparisons. 



TabLK I. — Showing rarintions in Alphcn.t saulcyi and the intermediate stiiges between the rarietiea 

breviearpus and lomjicarpus. 

1 



No. 


Sex. 


1 


<{ 


•2 


9 


a 


i 


4 


X 


5 


9 


6 


9 


7 


9 


8 


X 


9 


X 


10 


i 


11 


i 


IsJ 


X 


13 


-T 


14 


i 


15 


9 



Habitat. 



Leugtl). 



Green sponge. 



...do 

Urown sponge 

Green sponge.. 

Rocks; Dix Pt. reef . 



....do 

....do 

Rocks; Hog Id. reef. 
do 

Rocks; Green Key 
reef. 

Brown snongo 

....do ..". 

Rocks; Di.s Pt. reef. . 

Brown sponge 

Reef rocks 



mm. 
29.7 

42 

9 

9.5 
17 

10.4 
11.6 
10 
10 
9.5 

17.5 

i:< 

9. 5 
5. 5 
11 



Aural spine. 



Extends J length 2d seg- 
ment of antennnlar stalk 

To i 1. 2d segment 

do 

do 

i 1. 2d segment 



do 

1. of 1st segment 

Over ^ I. of 1st segment 

Nearly to end 1st segment, 
i I. let segment 



Nearly to end Ist segment. 
do 

i 1st segment 

do 

Nearly to end Ist segment. 



Squamona Bpine. 



Extends nearly to end of antennn- 
lar stalk. 

Do. 

Do. 

Do. 
Extends nearly to end of antennal 

stalk. 
Not nearly to end of antennal stalk. 

Do. 
}, 1. antennal stalk. 
More than }, antennal stalk. 
Nearly to end antennal stalk. 

^ antennal stalk. 

More than ^ antennal stalk. 

Do. 
J 1. antennal stalk. 
ii 1. antennal stalk. 



No. 



Inferior basal spine. 



i length sciuamous 
spine. 

Less than il. squa- 
mous spine. 
....do 



...do 



Nearly i 1. squa- 
mous spine. 
....do 



\ l.H(|uan)ou8 spine, 
jl. Hquamons spine. 



More than Jl. squa- 
mous spi ne. 



Nearly as long as 

squanions spine. 

....do 



Sqnaiue or scale. 



Scale as long as 
squamous spine. 
....do 

Scale nearly as 
longnssquamous 
spine. 

Scale somewhat 
shorter than 
squamous spine, 

Sculo not i|uite 1. 
N(|uanious spine. 

Small and rudimen- 
tarv. 

....do 

Rudiment 

....do 



Carpus of 

small chela. 



Short 
...do . 
...do . 



Rudiment (hardly 
visible). 

Rudiment 

No scale 

....do 

...do 



.do 



..do . 

Long. 
..do . 



Short 
Long., 

..do . 



.do 
.do 
.do 
.do 

.do 



Fingers of small cbela. 



Tipssiiiiple; no tuft 

on dactyle. 
Tipssiuple; no tuft. 



.do 



.do 



Tips simple; rudi- 
mentary tuft. 

Prongs ; tuft oVi 
dactyle. 



Tips simple; no tuft. 
Prongs and tuft 

Propodns ends in 
prongs. 

Prongs and tuft 

....do 

....do 

....do 



.do 



Remarks. 



Type of var. breviearpus. 
V. drawing, PI. iv. 
Claws dull red. 



Combines characters of 
both varieties. 



V. Fig, 13, PI. XXII. 

V. Fig. 14, PI. XXII, (outer 

antenna' from above). 
Dactyle missing. 

Claws reddish orange. 

Type of var. longicarpus. 
Rostrum wanting. 

Clawsbrightblue; dactyle 
of small chela extends 
1""" beyond propodus. 



S. Mis. 94- 



-25 



386 



MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



lu Nos. 1 to 4 we find little variation from tbe hrevicarpus form, which we consider as nearest 
to the type of the species. From No. 5 to No. 15 the departure from this type is increasingly 
evident, and in Nos. 12 to 15 we recognize the widest divergence in the varity longicarpus. 

No. 5 is an interesting case, since it combines the characters of both varieties. The aural 
spine is rather blunt and extends to one third the length of the second segment of the antcnular stalk. 
The inferior basal spine is rather less than one-half the length of squamous spine ; upper basal spine 
a rudimentary knob. The squamous spine has a well-developed squame; nearly equals length 
of antennal peduncle. The "finger" and "thumb" of small chela end in simple, sharply pointed 
hooks. There is an inconspicuous tuft of setie on the dactyle. The carpus is long. (See Table 11.) 

No. 8 is also an interesting variation. The anteunie are intermediate in character, between 
the extremes of the table, while the small chela is of the hrcvicarptis type. There is a rudimentary 
antennal scale. The tips of the small chela are simple. There is no tuft, and the carpus is short. 

In No. 9, which is of the same sex, the same length, anil from the same locality as No. 8, the 
small chela has the characters of the variety longicarpus. Nos. 5 to 12, in the middle of the table, 
show in one way or another intermediate characters between the extremes, Nos. 1 to 4 and Nos. 
12 to 15. 



TI. — MEASUEEMENTS IN MLLLEttETERS. 

Table ii. 

[Locality: Nassau, N, P., Bahama Islands.] 





Green 
sponge. 


Green 

sponge. 


Rocks: 
Dix Pt. 

Keef. 


Rooks : 

Green Key 

Reef. 


Eocks : 

Green Key 

Reef. 


Brown 
sponge. 


Rocks: 

Dix Pt. 

Reef. 




Sex 


9 


cT 


? 


<S 


? 


9 


9 




Number in Table 1 .... . 


2 


1 




10 


6 










42 
15 
11 
11 

a. 4 
1.5 
ih 

6.2 

5.1 

4.1 

4 

3.8 

5. 5 

4 

2 

6 

3 
2 

1 

1.1 
4 
1 
6 
9 

6.5 
4.6 
1.2 
4.7 
5 

1.9 
2.2 
0.3 
1.1 
2.0 
16 


29.7 
U 

1.7 


16 

7 
4 
4 


9.5 


10.4 
4.4 
2.3 
3 


11 
4.5 
2.1 


21 

8 
5 




Greatest witltli ot carapax .................. 




























Deptli of alxlonieii (with ova) ...... ...... .... .... 














Length of terga of abJoiuiual somites in mediau 
line : 


- 1.3 
2.8 
3 

3.3 
2.6 
2.6 
4 

3.2 
2 
5.2 

2.2 

'2 

1 

1 
3.7 
























Third 
























Fifth 












Sixth 
















































Len"'th of antennular stalli ...... . ........ 


2 

0.9 


1.8 

0.9 


1.8 


1.9 
1 


3.3 

2 


Length of autennular .segments : 


Second ... ...... ........... . 


Third 












Breadth of lirst antennular segment 












Len^^tli of antennular or aural t^pine 


1 


0.7 


0.7 


0.7 


2.3 






10 
5.5 
4.7 
1.0 
4 
4 

1.7 
2 
0.2 


"i.'ti' 


2 
3 
1.5 




1.8 
2.7 
1.5 


"'2."8" 








i.5 




Greate.st width of Ion**" segment...... ...... . 










Len"'th of sfinumous spine .................. 


1.4 


1 


1.2 

0.1 


0.9 


2.1 
1.9 


Leno'ihof "H<iuauie'' . .. .......... 


Width of spine and scale at base. ............... 






Len'^th of inferior basal spine ........... ..... 


0.9 


0.8 


0.7 


0.8 




Length of superior basal spur ........ ... . ... 














Length of same to articulation of squamous spine. 














15 




3+ 




5.8 


7 







MEMOIUS OF THE NATIONAL ACADEMY OF SCIENCES. 



387 



Table ii — Continued. 

(Locality : Naasaa, N. P., Bahama Islands. ] 



Habitat 



Green Oreen 

spttDge. spou<j:e 



Sex. 



Number in Table 1 



Length of |iropodiiH of large chela 

Leiifjth ofHaiiio to s|«iuo at base of dactylo 

Grealest width of saiiio 

Grivite.st dejilh of s.'iiiip 

Width of sarr.o at spiiio, at base of dactjio 

Length of " llmrnl. " of propodus 

Length of dactylo 

Width of same, over tooth 

Length of carpus of largo cheliped, ou upper me- 
dian line 

Length of nieros of same 

Greatest width of nieros of same 

Length of propodiis of small cheliped 

Length of same to articulation of dactyle 

Greatest width of same 

Greatest dejith of same 

Length of dactyle of same 

Width of dactyle of same 

Length of carpus of same 

Length of meros of same 

Greatest width of meros of same 

Length of carpns of second jioreiopod 

Length of tirst segment of carpus of same 

Length of tifth segment of carpus of same 

Length of second, third, and fourth segments of 
carpus of same 

Length of propodus of same 

Length of meros of same 

Length of propodus of third pereiopod 

Length of carpus of same 

Length of meros of same 

Length of i rotopodite of third pleopod 

Width of same 

Length of endopodite of same 

(Jreatest breadth of eudopodite of same 

Length of exoi)odito of uropod 

Breadth of same 

Length of eudopodite of uropod 

Breadth of same 



15 
II 



4 

4.f> 
5.'* 
4 
3 

2.8 
5.5 
:i 

().7 

4 

2.4 

l.H 

H 

1 

2.3 

G 

2.7 

7 

4 

1 

2 

2.2 

5.1 

5 

2.8 

6.2 

6 

1.2 

8 

2 

.5.8 

4.2 

5 

3.5 



16 

11 
6.1 
4.6 



6. 5 

6 

3 

2.4 

5.3 

2.6 

6 

3.1 

2 



3 

n.i) 



4.6 

2.7 

5.8 

1.9 

1.5 

3.5 

1.6 

4 

3.7 

3.7 

9.9 



Rorkn: 

Dis I't. 

Ri-if. 



Rockfl : I Rocks 

Grnen K<'V Oreen Key 

Reef. " Reef. 



:>. I 



1 

3 

1.7 

2.2 

1.8 
0. 9 



1 



1.9 

3 

0.8 



•I. 7 
4.4 
2.5 



2 
1 

0.8 
'2 r. 



2 

l.H 
0.8 



1.8 
0.8 
0.6 



n_„_„ I Rocks : 
"P""""- Keef. 



4.5 
3.4 
2 
1.4 



0.6 
2.0 



4.5 

3.4 

2 

1.4 

1 



0.6 
2 



1.7 



6 

4.4 

2.4 



2.0 
1.5 



1.3 
1 



1.7 



7.7 



VII. — THE CAUSES AND SIGNIFICANCE OF VARIATION IN ALPHEUS SAULCYI. 

If we consider Nos. 1 or 2 of Table 1 as representinjr tbe nearovSt api»roacli to the mean of tbe 
species, Nos. 5 to 15 must stand for individuals which have iluctuated farthest from the mean. 

The individuals given in the table were chosen without reference to sex, yet it appears that 
nearly two-thirds of the number are males. In examining a larger collection of these aberrant 
forms 1 find a still greater percentage of males. There can bo little doubt that in tho.se cases the 
males are in the excess, although I have not tested this point carefully. It is also evident from 
observation and detailed measurements that the average size of these abnormal individuals is less 
tliaii one-half that of the brevicarpus type. The brown sjjonges teem with a po[)ulation of uiider- 
sizA'd forms, nearly all of which are aberrant, and none of those which were examined exceeded 
tlie length of 17.5""", which is considerably less than the average for the type. 

Dow far are these variations individualistic and how far are they confined to the race or 
species as a whole! In other words, is the individual plastic, dei)artiiig from the standard of tlie 
species and becoming ditterent at different i)eriods of its life, or do individuals tleviate from the 
pieau of the species, each along its own line ? Further, are the variations cougenital 1 While we 



388 MEMOIRS OF THE NA.TIONAL ACADEMY OF SCIENCES. 

are uot prepared to answer these questions as fully as we could wish, yet the facts are sufiflcient 
to throw some light upon the subject. 

We have abundant evidence that there is considerable fluctuation in the life of the individual, 
as regards the number, color, and shape of pigment cells for instance. In all larvre of the.se i)rawns 
the external antennaj have a well developed scale, and it is thus clear that this organ may degenerate 
and apparently disappear, to be reconstructed again at a later period. The variety longicurpus (No. 
1.5, Table I) has no " squame," although it is present in the young (Fig. 7, PI. xxii), and the ca.ses in 
which the organ is seen in various stages of development (Figs. 13, 14, PI. xxii) support and illus 
trate this conclusion. This, however, is not a rule with the species as a whole, as it is in the some- 
what analogous case of the loss and subsequent reconstruction of the last two pairs of thoracic 
legs in the larvre of Stenopus and Sergestes. 

The question as to how far the characters which distinguish such forms as Nos. 1 and 15, Table 
I, are congenital can only be answered by a careful study of their development. My attention was 
not directed to this subject while at the seashore, and in this connection some interesting exi)«ri- 
inents remain to be performed. The evidence we have goes to show that the young in any given 
case share the peculiarities of the mother, and this is probably true of such details as the right and 
left handed condition of the large chelipeds. The following examples illustrate this fact: (1) The 
adult female in this case has the characters of No. 15, Table I. The autennular or aural spine is 
nearly three-fourths the length of the first antenuular segment. The aural spine has a correspond- 
ing length in the larvae of this prawn at the time of hatching. In the adult the fingers of the 
small chela end in prongs ; there is a tuft of peculiar set* on the dactyle. In the first larva the 
fingers of the small chela also end in prongs, and there is a tuft of rudimentary setie on the dac- 
tyle. In the adult the carpus of the small chelipod is relatively very long. In the first larva the 
carpus of this appendage is about one-third the length of the jiropodus (relatively a little shorter 
than in the adult). Fig. 11, PI. xxii, may be taken to represent the mother (rostrum here wanting), 
and Fig. 17 the young. The small chela of the mother is shown in Fig. 2, PI. xxiv, that of the young 
in Fig. 15, PI, xxri. Another case exactly liiie this was observed, where the embryo was taken 
from the abdomen of the female. (2) The adult in this case has the characteristics of No. 2, Table 
I (var. brevicarpus) (PI. IV, Figs. 1, 2). The larv;e are shown in PL xxi. Figs. 1, 2, 3, 8. The aural 
spine, at first short, is nearly as long as the first autennular segment when the larva is a week old 
(Fig. 10, PI. XXII). lu both the parent and young the carpus of the small cheliped is relatively 
short. The fingers of the small chela end in simple tips; there is no tuft on the dactyle (see 
Fig. 16, PI. XXII). 

These facts indicate that the young share the peculiarities of the parent, but exactly how far the 
individual may depart from this standard in its own life, or how strictly the law of inheritance 
applies in all cases, my observations do not warrant a decisive answer. A few experiments could be 
easily made upon this Alpheus which would throw light on some inteiesting questions in hereditj". 
The females with ova are easily obtained ; the young are readily hatched and kejit alive in glass 
dishes until they have reached the adult state. 

In this species the change of environment, due to the adoption of life in sponges, has probably 
acted as a direct stimulus to variation. These animals tend to vary most along certain detiuite 
lines, as, for instance, the relative lengths of the autennular segments and aural spine vary much, 
while those of the segments of the carpus of the second pair of thoracic legs are practically invari- 
able. Homologous parts vary alike, unless specially differentiated in diftereut ways, as in the 
chelipeds. There is no diversity of life between males and females, and both sexes vary alike, but 
aberrant males are probably the more common. 

The occurrence of large numbers of individuals showing variations of the same kind, but of 
different degree, render it plausible at least that the same variations may occur in a large number 
of individuals simultaneously, but the reason why this or that part has varied most is wholly 
obscure. 

The aberrant forms (variety longicarpus) which have adapted themselves to life in the brown 
sponge thrive and produce young which, in the early stages certainly, share in the peculiarities of 
the parent. The variety brevicarpus is similarly adapted to its environment and its young resemble 



MEMOIRS OF THR NATIONAL ACADEMY OF SCIENCES. 389 

it. Has natural selection, tlien, acted so far as to differentiate the species in more than one direc- 
tion ! There are some facts which fovor the view that it has done so, but before the question cun 
1)6 definitely settled we must determine more ])recisel.v how far intermediate or aberrant forms 
rei)resent phases of tiie individual and of the race. It is not probable that we are here dealing 
with the hybrids between two originally distinct species. 

Part Second, 
the development of alpheus. 

1. STRUCTURE OP THE LARVA. 

(PI. XLix, Via. I'-t- P^- Lni, Kig. 196. Pis. i.iv-Lvii.) 

These studies in the embryology of Alidieus begin with the growth of the ovarian egg and the 
early i)hases of segmentation and extend to tiie larval and adult periods. In order that the prog- 
ress of development may bo followed in the light of the structure wiiich the embryo finally attnins, 
we will start with a general survey of the anatomy of the first larva of Alphcus saiikyi. A fuller 
description of the histology and histogenesis of the tissues will be given in the parts which treat 
of the ditterent organs in detail. 

A profile view of the larva as it appears while still inclosed by the eggsiiell and of one imme- 
diately after hatching is seen in PI. xxi. Figs. 1 and 5, and the brief and insignificant metamor- 
phosis which is required to i>rovide it with the adult (!baracters are illustrated and describeil in 
a separate paper (Pis. xxi-xxtv). 

Most noteworthy are the large, stalked, compound eyes, the segmented abdomen provided 
with its full number of appendages, the short, stumpy antennic, and tlie swollen chelae or pincers 
of the first pair of thoracic legs. At this stage this .\lplieus is a larva, but in a restricted sense, 
since many adult characteristics are present. It is a larva, with i)reparations for immediately 
assuming the adult state. Some of the larval peculiarities are the spatulate telson, the biranious or 
schizopodal pereiopod.s (first to fourth pair, inclusive), the rudimentary pleopods, the unabsorV)ed 
food yolk, and the uncovered, stalked eyes. 

.The structural details are now very great, .so that it is often impossible to interpret the parts 
seen in a single section, and it is only by comparing sections made in different planes that the 
relations of the organs can be successfully made out. 

In Fig. 19G (PI. Liii) the plane of section is nearly vertical and median throughout, except 
for the posterior half of the abdomen. The supra-cesophageal ganglion, which is usually spoken of as 
" the brain "(s.o.f/.), is a complex organ, composed of internal, jncAhiWury innssci^{pi( nl-txuh.stanz halln), 
and cellular tissue which completely invests them. It is made up of the fused ganglia of at lease 
two segments, those of the first and second antennte. This fusion is complete from the early stages 
of development, and the relations of the parts are now extremely complex. They are best illus- 
trated by a comi)arison of the series of transver.se sections (Pis. liv, I.V, Figs. 211-219) with 
those made in a horizontiil plane (PI. LVii, Figs. 238-243), and it will be seen that there are four 
pairs of fibrous masses in the brain, intimately connected together. 

These compact and finely granular masses in the interior of the ganglia of invertebrates were 
described by Leydig twenty-five years ago under the name of Punkt.substnnz and later by Dietl 
(187C) as Marksubstanz. As Krieger remarks, the latter name is bad, since it confuses this tissue 
with the spinal marrow of vertebrates, with which it has nothing to do. It is essentially a/rlt of 
very fine fibers. \V«^ will therefore speak of it as the Punktsiibsfnnz, or, to use a more descriptive 
term, the Jibroiti subxtancc of the ganglia. 

The first i)air of these, the anterior or optic fihroux maiises (PI. LV, Figs. 212-21.5), are the 
largest. They are completely fused on the middle line and form a single compa(!t mass, which is 
slightly constricted laterally (PI, lvii, Fig. 242, of.) and which is divided in front (PI. liv, Fig.s. 
210, 211), where it gives oft" two diverging stems of fibrous tissue (sometimes (tailed optio nerrcs) to 
the optic gauglia in the stalks of the compound eyes (see also Pi. lvii, Fig. 210 of.). 



390 MEMOIES OF THE NATIONAL ACADEMY OP SCIENCES. 

Next in point of size are a pair of large lateral balls, which appear liicluey-shaped in transverse 
.section (PI. LV, Fig. 216, If.). Each is virtually segmented at the lower surface into two lobes (PI. 
LVii, Fig. 242, l.f.). These lobes are closely united to each other, and by a pedicel or stalk of 
libers to the lower posterior extremity of the anterior, optic mass. A third pair of fibrous masses 
(PI. L.V, Figs. 215, 210, «/.) fuse with the anterior mass at the same point. Each of these balls 
is also bilobed, and from them issue the fibers of the aiitennular nerves. (PI. LVII, Fig. 243, «. 
au., also PI. LV, Figs. 212-214, a. o., naii.) The nerve of the first i)air of antennie consists of 
cells and fibers, which pass to a mass of deeply staining cells {a. o.), the ear, and to the tissues of 
the anteunular stalk. The fourth pair of fibrous masses (PI. LV, Figs. 217, 218, gf., also PI. lvii, 
Fig. 243) are intimately associated with the last and with the common bridge of tissue (PI. LV, 
Fig. 216, of.) which unites them all. From these arise the fibrous elements of the antennal nerves, 
which supply the green gland and the tissues of the appendage (Fig. 216, n. ag.). From this 
same region (Fig. 218,/o.) the commissures which surround the oesophagus and unite the brain to 
the ventral nerve cord also originate (Fig. 220). These commissural bands meet immediately 
behind and below the oesophagus, where they fuse (PI. LV, Figs. 222, ocm.) and join the ventral 
chain of ganglia. This last consists of the ganglia of the remaining eighteen segments of the 
body. Each ganglion is double and is made up of two fibrous balls, united by a transverse 
commissure, and of a thick envelope of nerve cells. Longitudinal commissures of cells and 
neive fibers unite the successive ganglia, which form a double chain. These relations are well 
shown in Fig. 196 and by the horizontal section (PI. LVii, Fig. 243). The first six thoracic ganglia 
are very closely crowded together (Fig. 196, g. 4-9) and form what is usually known as the 
infra wsophageal ganglion (ganglia of mandibles, first and second maxillie, and first, second, and 
third maxillipeds). The next five ganglia, g. 10-14, which are less closely crowded than the 
preceding, belong to the five pairs of thoracic legs and their segments. The fiber balls of each 
ganglion are pear-shaped masses, disposed vertically, with the large end of the pear turned toward 
the base of the appendage. The abdominal ganglia are more widely separated and the longitud- 
inal commissures are consequently more marked (Fig. 196, g. 15-20; see also the series of trans- 
verse sections. Pis. LV, lvi). The nerves, always difficult to distinguish, owing to the close 
similarity of their cells to those of the surrounding ectoderm, are best exemplified in the case of 
the anteunular and antennal nerves already mentioned. 

The relations and course of the fibers, which are very complicated, are partially iudicated.in 
some of the sections. There is a marked transverse commissure of fibers in the anterior half of 
the large optic swelling (Fig. 213), and at its posterior extremity, where it fuses with the lateral 
and antennal masses (PI. Liii, Fig. 198, _(//.). 

The optic stalks or lobes, bearing the compound eyes (PI. liv, Figs. 209, 210, and PI. lvii. 
Figs. 239-242), consistof an irregular series of fibrous masses, in shape of a distorted letter L. 
The angle of the letter L is continuous with the fibrous substance of the brain, while its shorter limb 
proceeds to the compound eye and its longer forms a large swelling in the upper part of the stalk. 
There is a nauplius eye (PI. liii. Fig. 197; PI. liv, Figs. 209, 210, oe.) borne on a median papilla, 
which projects downward between the eye stalks. The details of the structure of the eyes are 
given in Section ix. 

Thealimentary tract of the larva is a somewhat complicated structure, and the relations of its 
parts are best undei'stood by reference to sections taken in more than one plane. We can recognize 
five well-defined portions: the tesophagus, the masticatory stomach, the midgut, the hindgut or 
intestine, and the appendages of the midgut. These are shown in asemidiagrammatic way in tlie 
cut (Fig. 2), and the longitudinal section (PI. Liii, Fig. 190) and series of transver.se and horizontal 
sections (Pis. lv-lvii) illustrate the stru(;tures in more detail. ' 

It is interesting at this point to compare the larva shown in Fig. 190 with the longitudinal 
section of an advanced embryo (PI. XLViii, Pig. 168). In both we recognize the foregut, a tube bent 
on itself, consisting of the tPsoi>hagus and masticatory stomach (Hi. s.). In the embryo the latter is 
closed on the sitle of the food yolk. In both we also see a vertically directed fold of endoderm (/., 
overlying mg^ In Fig. 190) and behind this the large lumen of the hindgut, which gradually tapers 
into that of the narrow, tubular intestine. Between this fold on the one hand ard the stomach on 
the other we find in the embryo an enormous space filled with yolk, which is partially walled in 



MEMOIKS OF THE NATIO^IAL ACADEMY OF SCIENCES. 391 

with endodermal epitlielimn near the point where it communicates with the cavity of the gut. 
This iu tlie larva correspond.s to the midgut (Fig. 196, mg.) and its diverticula. 

The (I'sopliagus (Figs. 106, 218-220) is a straight, vertical tube, with very thick walls, which 
are thrown into longitudinal folils. There is an anterior and posterior fold and two lateral ones, 
which give to the lumen of the resophagus the shape of the letter X when seen in transverse 
section (I'l. LVir, Figs. 241, 242). The walls of the masticatory stomach reseml)]e those of the 
(esophagus, and the folds of the latter nrv continuous with the vah uhir structures of this region. 
The lateral and median thickenings (PI. i.v, Fig. 221,2*. r.) at the point where this jiortion of 
the stomach passes into the iiiidgnt may be regarded as a rudirnentai-y ])ylori<! valve. The |>ouches 
formed between the median ventral fold (Fig. 221) and the lateral folds (;). r.) correspond to the 
gastrolith sacs in the craylish embryo (o4), but no gastrolitlis are found in Alpheus. 

The midgut appears in the longitudinal section (Fig. 19G, w[/.) as a short, iestri<;ted cavity. 
It is, however, a siiacious chamber, as we see by examining a series of se<;tions made in other ]ilanes 
(Pis. LV-i.VU). It consists of seven parts or divisions: a dorsal, unpaired, median division {mg. 
in all the figures), and, opening from this, a pair of anterior lobes (»ig.^), a pair of posterior (mg.') 
and a pair of ventral lobes {mg.''). All the.se parts are lined with a peculiar columnar ei)ithelium, 
composed of endodenn cells, derived primarily from the wandering cells, excepting a part of the 
median and the anterior divisions, where the endodermal wall is absent or only imperfectly formed. 
The epithelium of the midgut passes imperceptibly into that of the intestine, since the cavity of the 
hindgut is in communication with the food yolk from the very early stages of the embryo, and 
since also the endoderm is formed very gradually and first api)cars in the region where the hind 
gut communicates with the yolk. On the other hand, the demarcation between the wall of the 
inasti<!atory stomach (of ectoderuial origin) and that of the midgut (Fig. l!t(i) is most pronounced. 
Correlated with this distinction is the fact that the foregut is a blind sac and completely cut ott 
from communication witli the yolk until very late in embryonic life (PI. XLViii, Fig. 168). Tlie 
anterior lobes contain the remnant of unahsorbed yolk (Figs. 218, 2.37, _(/.), and in cases wliere the 
lining epitlielium is unformed, the food yolk is in contact with the brain. These lobes are sepa- 
rated by a median vertical i)artition {mp.), composed of connective tissue and muscle cells, which 
suspend this i)ortion of the digestive tract to the anterior dorsal wall of the body. In a very late 
embryo which is about ready to hatch we find that the partition separating the anlerior lobes is 
incomplete. The dorsal half of it consists of a <lown ward-growing fold of endoderm cell.s, with a 
mesodermic core. Tlie ventral and lateral walls of these diverticula are devoid of epithelium, so 
that the endoderu) extends itself most rapidly forward, on the dorsal median line, and thence spreads 
to the ventral floor. 

The posterior lobes {mg.'') are the first to develop (see PI Li, Fig. 185, mg.''). They lie to one side 
of and below the hindgut (PI. LVi, Figs. 226-2.30, «!//'., gg.^'-'). Up to this stage their position is never 
dorsal to other parts of the digestive tract. It is from these lobes that the gastric gland or so called 
" liver" arises. Each lobe is simple until a short time before the embryo hatches, but iu the newly 
born larva it is divided into three lobules. This division is effected in this manner: The lower 
median part of the primary lobe (Fig. 228, gg.') is constricted ott' by the growth of a fold from the 
side next to the hindgut, downwards and outwards, to form a secondary lobule {gg.^). By the 
constriction of the upper portion in the same way the primary lobe becomes divided into three 
pockets. The relations of the posterior division of the midgut to the unpaired central portion is be.st 
shown in a horizontal section (Figs. 236-238). It seems quite probable that a part of the ei)ithelial 
lining belonging to the enlarged section of the hindgut is endodermal in its origin, but just how 
much it is impossible to say. 

The ventral lobes (Fig. 224, mg.^) are ventro-lateral diverticula from the central portion of the 
midgut anil are completely lined with columnar epithelium. 

An examination of the structure of a young Alpheus of this species, ten days old, throws much 
light on tiio anatomy of tlio larva Just considered. The alimentary tract has at this time essen 
tially its adult structure. The gastric glands open into it by short ducts at a point just behind 
the masticatory stomach. They consi.st of three pairs of lobes or cieca. One pair, corresponding 
to the posterior division of the midgut (Fig. 226, mg.'), is imperfectly divided into tiirce lobules, 
as in the early larva. They extend backward, below and to one side of the gut. The two remaining 



392 MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. 

pairs pass forward on either side of the masticatory stomach to a point about on a level with the 
lirst maxillary segment. The ventral is the larger and louger of these, and two lobules are con- 
stricted off from it near its extremity. They correspond to the ventral lobes of the midgut {mg.^ 
cut, Fig. 2). The dorsal pair represent the anterior lobes (mg.'), which are now entirely withdrawn 
from the head region, and naturally contain uo food yolk. The gastric cffica are all tilled with a 
coagnlable fluid which stains feebly in carmine. The gastric epithelium for a short distance behind 
tiie point where glands communicate with the stomach has marked histological peculiarities. The 
internal absorbent surface is increased by folds which nearly obscure the lumen of the tube. The 
cells are columnar and resemble the glandular cells of the liver and probably have the same origin 
as the latter. In the masticatory stomach there is a strainer of hairs developed on the ventral 
and lateral walls which are greatly thickened, as we saw in the larva. The dorsal wall is thin, 
but there is a large valvular fold on the ventral side. 

The vascular system of the adult is already outlined in the larva in all its essential character- 
istics. Tlie walls of the blood vessels are exceedingly delicate, so that it is not easy to ascertain 
tiieir distribution by means of sections alone. The heart (PI. liii, Fig, 190, H.) is a short tubular 
cliamber, flattened between the dorsal body wall and the enlarged section of the hind gut. It is 
suspended in the pericardial sinus (j?. s.) to the body wall and surrounding organs by means of 
strands of connective tissue (alte-cordis). The walls of the heart are quite thin, and its cavity is 
l)artially divided into three compartments by the growth downward from its roof of two sheets of 
mesoderm cells (PI. lvi. Fig. 231, and PI. li. Fig. 186). 

Of the several arteries which lead from the heart, three, and possibly five, can be distinguished. 
Posteriorly the heart is continuous with the large superior abdominal artery, which traverses the 
abdomen close to the dorsal wall of the intestine (Figs. 196, 2.32, 235, a. s. a.). Near its origin 
from the heart, the sternal artery (Fig. 196 shows a trace of this vessel between ganglia 12 and 1.3, 
to the left ofpr.) is given off, and passes directly downward to the ventral nervous system, which it 
penetrates at a point between the third and fourth thoracic ganglia. This is continued backward 
under the nervous system and forms the inferior abdominal artery (Figs. 229-234, a. i. a.) Anteri- 
orly the heart gives off the unpaired ophthaJmic artery (Figs. 196, 215-229, op, a. op.), which runs for- 
ward to the region of the eyes and brain. It is not an oi)hthalmic artery, strictly speaking, but from 
the first, supplies arterial blood to the brain and anterior cephalic region generally. In Figs. 215, 
210, it is seen cut in partial longitudinal section, where it evidently communicates with the blood 
space surrounding this part of the brain. The antennal arteries can not be clearly distinguished 
in sections, but in a much earlier stage trains of cells are seen at-the surface of the egg passing 
forward on either side of the middle line toward the eye stalks, which jiossibly represent the anten- 
nal vessels. 

Besides the sinuses already mentioned, there is a large sternal sinus (Fig. 196, sts. s.). This 
occupies the extensive space between the thoracic ganglia and the alimentary tract and " liver," 
and, like all other similar spaces, is more or less completely tilled with serum and blood corpuscles. 

Five pairs of gills are present at this stage. They are developed from simple pouches or folds 
of the skin on the bases of the thoracic appeiidages (Figs. 193, 230-233, hr '' ^), The outer sur- 
face of this primary fold soon becomes divided into a number of secondary folds or gill plates, and 
in a larva which has moulted twice and is twenty-four hours old, the branchia has the structure 
shown in Fig. 195. The adult gill is precisely similar to this, except that it has a greater number of 
plates and more definite branchial vessels. In the early larval stages the skin and especially the 
branchiostegites (Fig. 193, bg.) probably serve as important respiratory organs. 

In respect to its muscular system the first larva ai»pears to differ but little from the adull. 
Tbe flexor and extensor mu.scles of the abdomen are most prominent (Fig. 196, nni. /., mii. r.). The 
former consists of a double rope of fibers, fuse 1 completely together and very much twisted. They 
extend from the sides of the thorax to the termiual telson (Fig. 227-235. mu.f.). The extensor 
muscles [mu. e.) are smaller, but otherwise similar to the latter, both in origin and extent. They 
lie above or to the sides of the digestive tract. Their attachment to the carapace is shown in 
Figs. 227, 228. 

The next most prominent muscles are the adducitors of the mandibles and great chelae. The 
former consists of a large band of fibers which pass from one side of the body to the other directly 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 393 

over till' nervous system (Fig. 221, ad. m.). Closely associatod with it are tiie muscles of tlic 
maxillie. Tiie large flat tendoi! to wbicli the acUlnctor muscle of the forceps is attached, is well 
developed at the time of hatching. It is formed liy the infolding of a sheet of ectoilerin cells at tli<i 
point of articulation of the fingers of the claws, and in a plane at right angles to their plauo of action. 
The outer ends of the cells of this infolded sheet now o[ti)ose each other and secrete the chitinous 
tendon, while to their morphologically inner ends the muscle libers are attached. 

The conuective tissues invest the organs aud seem to bind them together and to suspend them 
to the outer ectodermal wall of the body, but in some cases the ectoderm of the surface is apparently 
replaced by mesoderm cells, and often muscle fibers appear to be attached to the tergum of the 
somite (Fig. 196). This may be explained by the intimate fusion of the ectoblast and niesoblast at 
these points. 

The green gland (PI. Liii, Fig. 198, cuj.) at the base of the second antenna is a well defined 
structure. It consists of a blind tube, which passes up close to the brain as far as the anterior sacs 
of the nndgut, aud of a solid, di.sc, shaped body. The walls of the tube arc composed of a single 
layer of large cubical cells. These thin out at the lower end, and to the outer wall is applied the 
solid nodular boily. Neither at this stage nor at any previous one have I been able to detect an 
opening to the exterior. 

In the adult the tubular portion of the gland grows to very great length, coiling itself in all the 
available space in the anterior region of the body in front of the mandibles. It surrounds the brain 
and oesophagus and passes down to the labrum and into the eyestalks. The solid almond sliai)ed 
body (probably the end-sac) becomes a spongy mass of tissue. Its function is plainly different 
from that of the epithelium which forms the wall of the tube and to which the secretive product ot 
the gland is due. 

The reproductive organs, or what I regard as such, are ditBcult to find, owing to their very 
rudimentary condition. They consist of a small cluster of large cells on either side of the mid<lle 
line between the digestive tract and the anterior end of the heart (Stage x, Fig. 173, K. O.). 

With this sketch of the structure of the larva we are ready to trace the history of develop- 
ment from the earliest stages and to ascertain the manifold changes through which the uuicellidar 
egg with its great store of yolk jiasses, before it attains to the wonderful complexity of the larval 
and adult forms. 

II. — THE ORIGIN OF OVARIAN EGGS IN ALPHEUS, HOMARUS, AND PALINURUS. 

(a) Alpheus. — The ovaries of Alpheus are paired cylindrical bodies which extend between the 
alimentary tract and dorsal blood vessels, from just behind the eyes to the end of the third or 
fourth abdominal somite. Owing to the transparency of the skin in this species (.4. saulci/i) they 
are extremely conspicuous, giving to the female an intense green or yellow hue, according to the 
color of the egg (PI. iv). The oviducts open in the usual way by means of a slit-like valve on the 
biusal joint of the third pereiopods. 

In PI. XXVI, Fig. 11, the condition of the adult ovary is shown, as it appears two or three days 
after the eggs then carried on the abilominal appendages had been laid. The ovarian ova are 
ripe l)y the time the young are ready to leave the shell, and the new ova are laid in a few hours 
after the hatching of the larval brood. Tims there is a constant su(;(;ession of young, and females 
are not commonly foun<l without either attai;hed or large ovaiian eggs. The breeding season of 
this species extentls, as we have seen, throughout the entire year. 

The stru(!tur(^ of the ovary is (juite simple (Fig. 11). It is essentially a sac lined with ger- 
minal ei»ithelium. The external layer of the sac (O. W.) is muscular and contains numerous nuclei. 
Between the epithelium and fibrous coat there is a wide space filled with blood. This uuiy ho 
unnaturally large in the preparation owing to the disturbing edecUs of the reagents emphned, 
but it is not wiiolly abnormal. The germinal epithelium consists, for the most part, of a single 
layer of large cubical cells. The nuclei are large and granular, and the cell outlines are often 
distinct. The function of these epithelial cells is twofold: (1) They give rise to ova; (2) They 
form the epithelium of the egg follicle. 

There is no germogen or poly nuclear mass of protoplasm from which the ova are develojjed, 
but the eggs appear to originate directly from epithelial cells. The new eggs begin to develop. 



394 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 

while the ovariau lobe is yet ci'owded with ripe ova ready to be laid, on the ovariau wall uext the 
middle line of the body. The process seems to be as follows: The nuclei of the cells of the ger- 
minal epithelium increase in size along a certain tract. The cells grow rapidly and are slowly 
dehisced or pressed into the cavity of the sac. Each is surrounded by a coat of follicle cells. 
This is formed by the ingrowth of the germinal epithelium about the egg. Sometimes several 
ova occupy a common pouch (Ger.) which is separated from the rest of the ovary by sheets 
of follicular tissue (F. E.), but eventually each egg has a covering of its own. Between very 
young ova (e) no larger than the epithelial cell, and the maturer egg (e'j every stage can be 
traced. The yolk appears very early as a fine granular deposit in the protoplasm of the cell. 

In this species the development is nearly direct, there being no zoi'al stage, and the egg 
contains more than nine times as much yolk as the egg oi Alpkcus minus, in which the first larva 
is a zoi-a like form. The materials for the yolk must be derive<l directly from the blood, and in this 
form the germinal epithelium is bathed with the blood current. Where there is an enormous food 
yolk blood must be supplied to the developing ova in more than the usual quantity. This is often 
accomplished by reentrant blood sinuses which penetrate all parts of the ovarian stroma, as in 
the lobster [Homartis) and in the cephalopods, which are precocious in development and conse- 
quently deposit a great store of yolk in the egg. In the latter the follicular epithelium is folded 
in a remarkable manner about the egg to increase its nutritive surface. 

The germinal vesicle (Fig. H, G. V.) is filled with coarse chromatin grains, and in the early 
phases grows relatively faster than the rest of the egg. In the egg, (e,' to the left) which is ^^^ iw^'l^ 
in diameter, the diameter of the germinal vesicle is one-half that of the entire egg. The chromatin 
grains increase in size until there are formed, as in an egg like the last, six or more large masses 
of chromatin, or uncleoli. The older eggs are spherical ; their food yolk is often vacuolated, as in 
later stages, and they are invested by a single mend)rane, the chorion, which is a chitenous secre- 
tion of the follicular cells. 

In the ripe ovary of this Alpheus the mature eggs fill the ovarian sac, except at the lower 
portion uext the middle line, where, as already stated, the young ova first make their appearance. 
These mature eggs are closely crowded and irregular in shape, and their bulk greatly distends the 
body of the prawn. The chorion is now fully formed and closely invests the vitellus. The yolk 
is in the form of spherules, usually fused and always vacuolated in preparations which have been 
subjected to alcohol and turpentine. In the rijie egg the nucleus was not seen, but it is quite 
probable that careful sectioning would sbow that it lay at the surface, as is the case with the ripe 
ovarian egg of the lobster, which is often left in the ovary, after the bulk of the eggs are laid. 
We thus conclude that the extrusion of polar cells may be internal, that is, may take place within 
the ovary, as is sometimes, if not always, the case with Ilomarus. 

(b) The Lobster (Homarus americanus). — The ovaries of the lobster consist of two lobes or rods 
of tissue, united by a short transverse bar. When filled with eggs their color is a dark olivp 
green, except in young females, where the color of the immature ovary is variable. Each lobe is 
composed of an outer wall, which is a felt of muscle and connective tissue fibers with very small 
nuclei, and of a loose framework of germinal epithelium, which penetrates all parts of the lobe. 
The latter is a syncytium and consists of a matrix in which great numbers of small nuclei are 
embedded. These nuclei, with surrounding protophxsm, give rise (1) to ova and (2) to cells of the 
egg follicle. 

The growth of the ovarian egg from the epithelial nucleus is illustrated in PI. xxv, Figs. 3, 6. 
Fig. G is from a section through the posterior end of an ovarian lobe of a lobster obtained from the 
Baltimore markets in January. Fig. 3 shows the central portion of this section greatly enlarged 
The diameter of the entire section is about twice that of the part represented in Fig. 6, and the 
oldest eggs lie at the periphery. The germogeus, the centers of dis])ersion of new eggs, lie nearly 
in the long axis of the lobe. We can therefore trace in a single good section at this stage the de- 
velopment of the egg through every stage, from the indiftercut nuclei of the ovarian stroma to the 
large peripheral ova. The ovary is supjilied with blood by means of sinuses which i)enetrate to 
all its parts (Bl. S.). The sinuses are definite reentrant channels with thin membranous walls. 

The ovarian tissue (Ct. S.) consists of a fibrous matrix in which numerous oval granular nuclei 
are embedded. The process of the conversion of the epithelial cells into eggs is shown in Fig. 3. 
The epithelial nucleus (O, O^} swells out, becomes sx)herical, and its chromatin has the charac- 



MEMOIliS OF TUE NATIONAL ACADEMY OF SCIENCES. 395 

teristic grauiiliir appearance of the j^eriiiiiial vesicle of tlie i oniig egg. The first trace of tlie yolk 
(O', O^, O^) appears in tlio outer granular layer which surrouuds the germinal vesicle. Thi.s layer 
represents primarily the cell protoplasm, in which the yolk is formed. The cell takes on a (Iclinite 
shape and is very early invested with a follicnlar coat (F. C). In an egg a little older (O") the 
nucleolus has appeared, and in still older eggs (Fig. G, O, O') a delicate chorion (Ch.) can be 
seen. This is secreted by the (^ells of the follicnlar envelope (F. C). The growing eggs pass out 
from the central to the perii)heral parts of the lobe in the sheets of stroma Ix^tween the blood 
sinuses. Distinct yolk sphendes are very early seen (O') and are of uniform size, but in maturer 
eggs (Fig. G, O, O') the germinal vesicle is sometimes surrounded by a central layer of small 
spherules ami a peripheral layer of larger ones. The germiiial vesicle is centrally situated and 
always contains a single excentric nucleolus, besides stellate masses in the chromatin reti<;nlum.* 
(v) The Spiny iois^cr (Palinurns). — In the spiny or rock lobster from the Bahamas the ova 
originate exactly as in Ilomarus, and the structure of the ovary is essentially the same. There 
are several nucleoli, as in Alpheus. The ovary is not nearly so richly su])plied with blood sinuses 
as in the cases just considered. This is perhaps correlated with the fact that the amount of yolk 



• Since the above account was written I have been able to stndy the strnctnro of the ovary more thoronghly, 
and the subjoined notes are largely extr.acted from a preliminary notice on "The Reproductive Organs and Early 
Stages of Development of the American Lobster." (23.) 

The strnctnre of the mature ovary is somewhat peculiar. The free, unextruded eggs lill the lumen of the 
ovarian lobes. The lobe or tube itself consists of the proper ovarian tissue and the outer uiusenlar wall, which is 
very thick. The stroma is characterized by the presi'uce of (jhind-Uke struclun-n, blood sinuses, and immature ova. 
The glands are in close relation with the growing eggs. They are plaited or folded strinturcs, and consi.st of a single 
layer of columnar cells, the boundaries of which are indistinct. The lumen of the fold usually contains a granular 
residue, but often yolk and degenerating nuclei. It seems possible that these structures are comparable to yolk 
glands, and that their fuuctiou is to supply the growing ova at this stage with a part of their massive food yolk. 
Three days after the extrusion of the eggs the glandular c:eca have much thicker walls; the rapidly dividing cells 
are smaller, and their nuclei lie .at various levels. In another ovary of about the same age the glands are relatively 
very large. The columnar cells are greatly elongated, their nuclei lie at the deeper or outer ends of the cells, .and 
the lumen of the gland is often completely obscured. The gland forms a kind of egg tube, abutting upon and partly 
inclosing the growing egg. The columnar cells stop short at the sides of the egg, so that the glandular ciccum resem- 
bles a narrow bag with an egg pu.shed into its mouth. The glandular cells are directly continuous with those of (he 
follicle. The axial portion of this ovarian lobe is composed of hollow spaces, blood sinuses, and loose stroiiia, in 
which very young eggs occur. Degenerating cells occur not only in the stroma, l)ut probably in the developing ova 
also. In Peripattia Xova; Zcalandkr the yolk is described by Lilian Sheldon as arising not only from the egg proto- 
plasm, but .also from the follicle cells (T)?). 

When ten to tifteen days have elapsed after egg-laying (eggs in egg-uauplius stage), the gland-like bodies 
have almost wholly disappeared. The walls of the ca-ca are shrunken and crumpled, and the latter have been 
crowded to the extreme perijihery of tho ovary. The ovary now contains a solid core of innuature eggs, stroma, and 
bloodvessels. This is continuous with radial sheets of similar tissue which extend from the center toward the pe- 
riphery. The outer and more mature masses of ova are thus divided into more or less continuous, longitudinal b.ands. 

At a still later period (eggs with eye pigment, four to five weeks' old ) the glands are j)resent nn-rely as 
shriveled remn.ants. Later still (lobster taken August 21 ; egg embryos in <a late staged there is no trace of glaml-liko 
structures. In the ovary of a lobster (taken June 30), with eggs about to hatch, the condition is similar to the last. 
It is m)w .about eleven months sinre the eggs wore laid, yet the diameter of the largest ovarian ova is only about on< - 
half that of tlu! mature eggs. The ovarian wall is thinner than in previous stages, .and in the axis of the lobe there 
are still sheets of very small, immature ova. 

It seems that the bodies which have been described as probable yolk glands are present in the peripheral 
parts of the ovaries only during tln^ limited pi'riod of from two to throe weeks after the eggs are laid, and when the 
org ins are recovering from th<^ changes which follow this event. Their strm;ture is quite unlike th.at of bloodvessels 
or sinuses with which they are intricately associated, and their relation to the growing eggs seems to imply thai 
they have some functtion to perform in tho nourishment of the peripheral ova. Their short existence, on tho other 
hand, might lead us to suspect that they were more or less rudimentary structures, or that they wore concerned with 
the secretion of the gluey substance with which the eggs are coated at tho time they are laid. Their true function, 
however, remains to bo determined. 

Ovaries which I have examined, taken in summer (.Inly) from lobsters ( "paper shells") which have roci-ntly 
moulted aud which do not carry eggs, present very thin w.alls, ,an<l the largest ovum measures in diameter about one- 
half that of tho mature egg. These lobsters have probably hatched a brood the present season .and have afterwards 
moulted. (Compare tho ovary of the Inbster taken .June 30 above.) 

Some allowance is to bo made for individual ditVerence, but the slow growth of the ov.ariau egg, which wo 
have traced from the summer when eggs were laid to toe following summer when these eggs were hatched, is very 
noteworthy, and shows conclusively that the lobster is not an annual breeder. 



396 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

in eacb egg is very small, although the number of eggs produced by this animal is euormous. At 
Nassau, Palimirus begins to spawn in June. 

{d) CowyjarwoH.— Ishikawa describes very fully the ovaries and ovigenesis of the prawn At- 
■yejjhyra compressa and concludes that the ovum "originates from the inner lining of the ovary and 
is at the beginning a cell with a nucleus and one, two, or rarely three nucleoli.' The mature egg, 
according to this observer, has two membranes, one of which is due to the "hardening of the 
peripheral protoplasm of the egg," while the other (secondary egg-membrane) is secreted by the 
epithelial cells of the oviduct and added at the time the eggs are laid. 

There seems to be an error here in regard to the origin of the chorion. In the Decapod Crus- 
tacea it is the rule that the choriou it secreted gradually during the growth of the egg by the cells 
of the egg follicle. The large glandular cells found in the oviducts of Atyephyra possibly secrete 
the viscid lluid by which the eggs are attached to the swimmerets, yet this point needs comfir- 
mation. 

The chorion was found in the ovarian egg of Pagurns by Mayer (39), who says : 

Das Eierstocksei von Pagurus ist in der ersten Zeit seines Bestebens eine eehte Zelle niit Protoplasma, Kern und 
Kern-Korpercbcn. Spiiter findet oine Einlageruug von Deutoplasma und die Bildung eiuer HUHe ans Chitin statt. 
Eudlich wild der Kern unsichtbar; das Ei stellt dann eine Cytode vor. 

Das fertigo Ei verliisst den Leib des Krebses ohne Kern und mit einer Hiille versehen. 

This description answers for Alpheus in all essential points. 

The ripe egg of the crayfish (Astacus fluviatUk) is inclosed by a single envelope, the chorion. 
According to Ludwig and Waldeyer it is not known whether this is a product of the egg or of the 
follicle cells. Huxley (26) merely states that " a structureless vitelline membrane is formed between 
the vitellus and the cells which line the ovisac." The ovisacs burst and the ova pass through the 
ovary into the oviduct. When laid, the eggs " are invested by a viscous, transparent substance 
which attaches them to the swimmerets of the female and then sets." Here as in other forms the 
chorion is clearly the secretion product of the ovisac. 

In Granyon vulgaris Kingsley (31) finds that the late ovarian ova resemble the newly laid 
eggs. There is a thin structureless envelope (choriou), but no trace of an inner vitelline membrane. 

Ludwig's general statement that the egg cells of ail Arthropods are surrounded by a vitelline 
membrane (Dotterhaut), the product of the egg itself, is certainly erroneous. He divides the egg 
membranes into primary egg membranes, those which are derived from the i)rotoplasm of the egg 
itself or from its follicle cells, and secondary egg membranes, those formed by the wall of the oviduct 
or otherwise. Balfour, following Van Benedeu, restricts the term vitelline membrane to structures 
derived from the protoplasm of the ovum, and chorion to those formed by the cells of the follicle 
or oviduct. In the categoiy of secondary structures would fall also those secreted by speci.al 
glands, found, according to Ludwig, in Trombidium, Chilopoda, and nearly all Crustacea, and the 
winter eggs of Daphnia and Tardigrada, which Is due to a moult or direct sex^aration of epithelium 
from the body of the mother. 

In speaking of the vitelline membrane Van Beneden and Bessels, in their monograph on the 
formation of the blastoderm (60), thus define it : 

Nous entendons la membrane vitelline dans le sens oii M. Claparcdo I'a si ncttement diSlinie dans son travail snr 
les vers Nematodes : C'eet la concbe externe dn protoplasma de la-nf, qni, ayant acquis nne density plus graude que 
la masse sous-jacente, se s^pare de celle-ci par un contour net et trancbi?. Elle est il I'ceuf ce que la membrane cellu- 
laire est h, la cellule ; elle se forme de la meme manifere. 

According to this view the ovum is morphologically a cell, the vitelline membrane is the cell 
wall. 

The origin and growth of the egg in Amphipods iOammarus locvsta) agrees quite closely with 
what takes place in Alpheus and Homarus. According to Van Beneden and Bessels (60) the 
young ova are at first protoplasmic cells, the nucleus of which becomes the germinal vesicle. The 
ovarian egg is a cell without a membrane, and in the cell protoplasm refringent vesicles are devel- 
oped which form the yolk elements. According to these authors the mature ovarian egg consists 
of a viscous, finely granular, and contractile liquid, which represents the primitive cell j)rotoplasm 
and holds in suspension the germinal vesicle, and, secondly, of nutritive yolk elements (called by 
them deutoplasm because of secondary origin), which are also suspended in the protoplasm of the 
egg. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 397 

In insects it appears that a clioriou is always present in ovarian eggs, wliile, on the other 
hand, arachnids possess a vitelline membrane and the eggshell is secreted in the oviduct. 

There is no sini|)le rule to express the appearance of egg membranes in a diversified gronji 
like the Artliropods, and, considering tliat these struetnres are purely secondary to the cell and 
expensive products however formed, this is what we should expect. Their function is chiefly pro- 
tective, and wliere a chorion is present in tlie ovary a yolk membrane is not developed, bnt the 
latter is present, as in spiders, when the shell is a later product. Erdl (15) describes tluee egg- 
membranes for the lobster, but it is clear, as Mayer has already shown, jliat the inner, delicate 
membrane which has been described for the decapod egg, is a secretion j)rodnct of the blastoderm. 

III. SEGMENTATION OF THE EGG OF ALl'HEUS MINUS. 

In the small green Alpheus of the southern coast we have a peculiar modification of the usual 
process of segmentation, which seems to be anomalous. 

The fertile egg is pervaded with a remarkably fine reticulum, which incloses yolk s[)herules 
of minute aud uniform size. The nucleus is central, or nearly so,* and consists of an ill-defined 
mass of protoplasm, in whicli a fine chromatin network is suspended. In the next i)hase (J'l. xxvi, 
Fig. 14) the nucleus is elongated and about to divide. Division appears to be direct and irregular. 
At a somewhat later stage the j)henomeua of the most interest occur (Figs. 12, 13). Each product 
of the first nucleus has developed a swarm of nuclear bodies (S. S.), which seem to arise by fragmen- 
tation. These bodies take the form of spherical nuclei in clear masses of protoplasm. The yolk 
frequently has a tenileucy to segment about the nuclear masses, in the same way that it divides 
about a single nucleus to form a yolk pyramid. This yolk segmentation seems to be normal, but 
it is very irregular. lu oue case there were two large segments, which nearly divided the egg in 
two, besides several smaller ones. Nuclear matter consists either of small jtarticles or of indefi- 
nite reticulated masses, resembling the first nucleus (Fig. li). Clear areas are sometimes found- 
with nuclei which appear to be breaking down. About eightuuclear swarms or clusters are present 
in the stage shown in Figs. 12, 13. The nuclei vary in size from refringeut particles to bodies of 
ordinary nuclear appearance. 

Figs. 25 and 26 represent two sections of oue Of the clear areas in the same egg from which 
Fig. 12 was drawn. This clear field has several degenerating nuclei near its border. Tlie largest 
one (S. C.) is included in both sections. A small chromatin mass with indistinct body lies next 
it (S. C), aud other similar bodies occur in difl'ereut sections. The cell S. C. contains two chro- 
matin balls, and in Fig. 26 (the next section but oue in the series) tbis body appears to be dis- 
charging through its broken-down wall numerous minute elements (S.) into the clear field. In 
Fig. 22 a small protoplasmic area occurs, in which a single nucleus lies. This body is granular 
and contains a large chromatin ball. Figs. 5 aud 23 are also from the same egg. Uere we see 
structures similar to the cell just mentioned. They are surrounded by yolk aud consist of a deli- 
cate reticulum in which usually oue large nucleolus is suspended, besides great numbers of small 
chromatin particles. 

Various stages of growth aj-e here represented, aud it might appear at first sight that we have 
a case of endogenous cell formation. I see no reason to suppose that the eggs examined are abnor- 
mnl, aud I conclude that we rather have in this specties a remarkable modification of the usual 
indirect cell division, attended by an equally remarkable degeneration oi nuclear material. 

In the last stage obtained (Fig. 29) the whole egg is tilled with several hundred very large 
elements, which are descended more or less directly from some of the nuclear bodies Just consid- 
ered, but the intermediate stages have not been traced. This probably corresponds to stage vi of 
A. saulcyi, at the period just before invagination, but it is quite unlike anything which I have seen 
in other species. The yolk is now irregularly segmented into blocks or balls, but probably not 
with refeience to these cells. 

This case is interesting when we compare it with the degeneration of cells to be described in 
another section, and from a cytological i)oiut of view it deserves careful study. 



• In singlo sections tlio ouclcns is strictly central, bnt wht-ther it is so with respect to tho entire e;;K it is not easy 
to deteruiiue. Minot states tbat the egg nucleus is always eccentric— Jni. Naturaliet, Vol. xxiii, 1889. 



398 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

IV. — THE DEVELOPMENT OF THE EMBRYO. 

Stage I. — Segmentation to formation of the blastoderm. 

These observations relate to Alphevs heterocheUs of the Southeru States, to a Bahaman form 
which hatches as a zoea but which otherwise resembles this species very closely, and to Alpheus 
mulcyi, also the from Bahamas, which has large eggs and a nearly direct development. Except 
where it is necessary to mention specific differences, these three species will be treated as one form. 

In June two Alphei {A. saulcyi) laid eggs in an aquarium, but the ova were in each case 
unfertilized, and for the most part failed to adhere to the swimmerets. One of these eggs, hardened 
at an interval of five hours after it was laid, is shown in section on PI. xxvii, Fig. 17. I regard 
the nucleus of this egg as the female pronucleus. It consists of clear protoplasm, which stains 
ieebly and sends out processes on all sides into the yolk, and of an indefinite chromatin networic 
susi)ended in it. The massive yolk is composed of corpuscles of uniform size, excepting at the 
periphery where they are much smaller. Numerous small lacunae occur, representing jiarts of the 
yolk which were soluble in the reagents employed. The chorion, or inner egg-membrane, is 
transparent, tough, and very distensible. It frequently splits into thin layers when subjected to 
the hardening and embedding process, thus showing the manner in which it is formed in the 
egg-follicle. It thus appears that the unfertilized egg of Alpheus is incapable of segmentation. 

The first segmentation nucleus has been observed in a few cases. That shown in Fig. 16 is 
possibly preparing for division. It possesses a fine reticulum ; it is lenticular in shape, and granular 
in appearance, and is surrounded by protoplasm which spreads into the yolk. The ouce divided 
nucleus and the next phase with four cells were not obtained in Alpheus, but the latter was seen 
in an allied prawn (Pontonia domestica}, and is shown in Fig. 27. One of the three cells present is 
in the aster stage of karyokinesis and has a well-marked equatorial plate. The third segmenta- 
tion phase is illustrated in Figs. 9, 28, and 30. In the section through the entire egg, three of the 
eight cells present are met with, and one of these (x) is shown with greater detail in Fig. 30. A 
cell in process of division is represented in Fig. 28. In another egg with eight cells present, two 
are undergoing division in different planes. As before, the cells consist of a chromatin network 
of various shapes surrounded by a clear protoplasmic body, which sends out processes between the 
surrounding yolk spheres. It is important to notice that the products of the segmentation of the 
first nuclr^us pass gradually and uniformly to the surface of the egg. At this stage they have not 
reached the surface but are visible through the egg shell. The yolk in these specimens consists of 
spherules or angular blocks (Fig. 28, Y. S.), which are largest in the center of the egg, and con- 
tain very few vacuoles. 

The fourth phase of segmentation is attended by the cleavage of the superficial i)arts of the 
yolk (Fig. 10) around the nuclei, thus giving rise to sixteen blastomeres or partial yolk i)yramids. 
The division of the yolk proceeds but a short distance below the level of the nuclei, so that all the 
yolk-pyramids open by their inner ends into the common yolk mass which fills the segmentation 
cavity of the egg. The base of the pyramid, which abuts on the surface is polygonal in shape, and 
at its middle point some distance below the surface, the nucleus is seen with its investments of 
protoplasm. The nucleus is large and granular, and the protoplasm which surrounds it reaches 
out on all sides into the yolk. We may look upon the yolk pyramid as a cell in the strict morpho- 
logical sense, its protoplasm being concentrated about the nucleus. The blastoderm or primitive 
egg envelope arises through the multiplication and consequent reduction in size of these huge 
yolk elements. The surface has then the usual appearance of a fine mosaic of hexagonal i)lates 
or cells, the nuclei and surrounding protoplasm of which lie at the surface. 

The fifth segmentation phase is shown in Figs. 15 and 31. The septum between the pyramids 
extends farther into the yolk, while the nuclei are slightly nearer the surface, and the long axis of 
each is parallel with it. This particular egg was taken in a period of " rest," but in others the 
nuclei are in karyokinesis, the division being always radial or in a plane at right angles to a 
surface tangent. 

The segmenting egg of Hippa talpoides is shown in Fig. 1 (32-cell stage;, and a section of a 
later phase in Fig. 4. The egg appears to have undergone a total segmentation when seen 
from the surface, but this is not quite so marked as represented in the sketch. The yolk pyramids 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 399 

(Fig. t, Y. P.) agree with those in AlplicHS and are ]»robal)ly formed in a siniihir way. In Paltv- 
inoHctcs I'ulgaris the history of segmentation appears to be essentially the same. The nucleus 
and biuse of one of the yolk i)yramids of this form is shown in Fig. 24. Ilerewe see that the peri- 
nn<-lear jjiotoplasin has a rayed ai)pearance, being produced in all directions into very delicate 
threads which ramify among the yolk spherules. Some of these threads moreover unite witii a 
thin septum (Sep.) which forms the boundary wall between two adjacent yolk pyramids. 

Segmentation proceeds with a regular rhythm up to the fifth stage, but beyond this it soon 
becomes irregular. A blastula is thus formed, consisting of a single layer of cells or hiastoderm, 
and the inclosed central yolk. All the nuclei reach the surface and take part in forming the 
blastoderm, so that all the protoplasm of the egg which is at first central or internal, comes gradually 
to assume in the course of seguientatioii an external position with respect to the food yolk. The 
blastodermic cell is the direct descendant of the yolk pyramid. It is improbable that the yolk con- 
tains any active i)rotoplasm, excei)ting that which radiates from the nuclei, and which is descended 
from the perinuclear protoplasm of the first segmentation nucleus. 

Stage II.— The blastoderm and invagination. 

The prawn when discovered with eggs in the fifth stage of segmentation (Fig. 1.5) was kept 
in an a<iuarium, and the ova were preserved at intervals of several hours. Thus it has been 
possible to follow the changes which take place between segmentation and invagination with 
considerable detail. 

V The egg represented in Fig. 47 is about 15 hours older than last described (Fig. 15). Cell 
division, which is now irregular, has become accelerated over a part of the egg so that a germinal 
area or disk (G. D.) representing the future embryo is formed. The side of the egg shown in 
Fig. 47 corresponds to that occupied by the germinal disk. In reverse view there are much fewer 
nuclei. The egg has thus lost its radial syn)metry and become two sided. Invagination soon 
follows this stage" at a certain point in the germinal area (G. D.). The superficial cells of the 
blastoderm (Fig. 48) are about one-third their former size, but they still have the characteristics 
of the yolk j)yramids. The cell is polygonal in surface views; the nucleus is surrounded by yolk 
and tlie cleavage planes between adjacent cells (Fig. 38, Sep.) are still present. 

This stage is characterized by the passage of large numbers of cells from the surface to the 
central i)arts of the egg just before the invagination takes place. This process is well illustrated 
bj' a series of consecutive sections (Figs. 38-44) taken from the same egg. In all these sections 
the cleavage of the yolk can still be seen. Many of the blastoderm cells (Fig. 39, a.) are in different 
phases of division, thc^lividing plane being always perpendicular to a surface tangent. It is 
l)robable, therefore, that the nuclei with their perinuclear protoplasm, leave the yolk pyramid 
and pass by arufcboid movement into the interior. It is, therefore, evident that while morpholog- 
ically the yolk pyramid is a cell, the elements which pass into the egg have also the value of 
cells in a physiological sense. Six nuclei are met with in Fig. 38, one of which has wandered 
some distance from the surface. In the next (Fig. 30) two cells (a. a'.) are in the aster phase 
of division ; one (a^) has passed just below the surface, and another (a^) is near the center of the 
egg. These cells (a, a'*, a^) are sectioned again in the following figure (Fig. 40). Various i)hases 
of the process of migration* are seen in other members of this series. In an enlarged portion 
of a similar section (Fig. 37) several cells are met with, some at the surface just beneath the 
shell, and others at some distance below it. The protoplasm about the nucleus has no defi- 
nite bounds, and is often filled with fine particles of food yolk. It is thus evident that these cells 
feed essentially like amceba', by taking the food directly into the protoplasm of the cell. 

The critical stage at which cells begin to pass from the superficial to the central parts of the 
yolk was obtained in an egg just thirteen hours older than the fifth segmentation phase, shown in 
Fig. 15. There arc about a dozen yolk cells in this egg, and one of these is in karyokinesis. The 
remainder lie very near the surface, but for the most part are 8ei)arated from it by a thin layer of 
yolk s])liere8. It is thus clear that the migration of cells to the central parts of the egg begins 

* lu tliti lolistrr tho primary yolk cells arise l)y (Iclamiuatinii, and as suggestoil iu Section V, tbis is possibly true 
of Alpbeus. 



400 MEMOIRS OF TEE NATIONAL ACADEMY OF SCIENCES. 

before all the protoplasm, that is, tlie nuclei and perinuclear protoplasm of tlie yolk pyramids, 
has reached the surface. In the slightly older idiase, shown in PI. xxx, Fig. 4«, all the proto- 
l)lasm which does not pass inward is strictly superficial. Tlie yolk has the same appearance as 
in previous stages, and, as already noticed, the cleavage i)lanes (Sep.) between yolk pyramids are 
still met with. Very soon, however, the central portion of the yolk segments into biills or angular 
blocks (Fig. 46, Y. B.), apparently with reference to these wandering cells. A section through the 
germinal disk of an egg seven and one-half hours older than that shown in Fig. 47 is given in Fig. 
57. The cells in the area of the germinal disk are (piite closely crowded, and the superticial seg- 
mentation of the yolk is still apparent. We now have a primitive epiblast, or external layer of 
cells, and a primitive hypoblast, composed of yolk <'ells which have migrated from the blastoderm. 

The invagination stage immediately follows that last described (PI. xxxi). A slight depres- 
iou occurs at a point on one side of the germinal disk, where the cells are multiplying most 
rapidly, and numerous cells pass downward into the yolk. The invagination is nearly solid, and 
the segmentation cavity is still filled with the great mass of yolk and with primitive hypoblast. 
In the crayfish (Astacws fluviatilis) the invaginate cavity becomes a closed chamber within the 
yolk (54), and this is eventually converted into the midgut, but in most decapods the pit is very 
small and the mesenteron is formed independently at a later period. A line drawn through the 
pit and the middle of the germinal disk marks the long axis of the embryo, and the point of 
ingrowth is at the posterior end. 

The structure of the embryo is illustrated by a series of transverse sections (PI. xxxi). The 
cells in the center of the egg represent the primitive hyjjoblast or yolk cells. The nuclei are 
large and granular, and sometimes occupy the center of a yolk ball. In Fig. 4!) the posterior edge 
of the embrjo is sectioned, and the three following sections (Figs. 50-53) pass through the region 
corresponding to the invaginate area (Igf). Fig. .52 represents the entire "gectiou, of which Fig. 
51 is a part. The pyrami'dal cells, which form the lloor of the depression, contain at their 
peripheral ends no unabsorbed yolk, but at the deeper ends of the cell, below the level of the 
nucleus, the cell boundaries are lost, and the protoplasm of the cell blends off into the yolk and 
ingulfs its finely divided i)articles (Fig. 50). Numerous cells (Figs. 52-54, b, b^ =) have already 
wandered from the point of invagination into the egg and a considerable distance forward under 
the germinal disk (Fig. 54, G. D.). These cells are more or less intimately united by pseudopodal 
extensions of the protoplasm. A coarse reticulum is thus formed, the meshes of which are filled 
with yolk. In front of the invaginate cells, the germinal disk (Fig. 55, G. D.) is still one cell 
thick. At the close of the invagination stage the primitive hypoblast has received a consid- 
erable accsssion of wandering cells. This .stage is usually described as the "egg-gastrula," 
in accordance with the theory that it represents an ancestral condition, and that the cavity 
formed at the surface is the remnant of the primitive digestive tract. The discovery of delami- 
nation, the actual separation of the inner ends of the cells of the blastula by karyokinesis before 
any invagination occurs, as I have described in the lobster, and the occurrence of this or of mul- 
tipolar emigration in Alpheus, together with the fact that in the typical decapod the invagination 
has no direct relation to the digestive tract or to to the mouth and anus, point to the view already 
expressed in a preliminary paper upon the lobster (25), that the invagination stage has no refer- 
ence to an ancestral invaginate gastrula. It seems to me more probable that the egg with primary 
yolk cells corresponds to the ccelenterate plauula stage, and that these yolk cells, which originate 
from the blastula and which i)artially or entirely degenerate, represent the remains of a i)rimitive 
hypoblast. According to this view the invagination is a secondary process, which became so 
indelibly impressed upon the ancestors of the Decapods that it has remained in the ontogeny of 
present forms. The conditions which are found in the crayfish can not be regarded as in any 
sense general or typical. 

Stage III. — Optic disks and ventral plate formed. 

This stage (Fig. 58) is characterized by a thickening of epiblast which gives rise to the tho- 
racic-abdominal or ventral plate in front of and around the point of ingrowth, by the simultaneous 
spreading of invaginate cells below the surface, and by the appearance of the optic disks (O. D.), 



MKMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 401 

two patches ot ectohlast on citlier side of the middle line in front of the ventral plate. When 
the living egg is examined by reflected light these structures appear as misty white patches sep- 
arate from each oilier. (See Fig. 2.) 

The i»rincipal tell mass is the thoracic-abdominal i)Iate (Fig. 58, Ab. P.), from which the 
thoracic-abdominal process is developed. The position of the pit (Ig.) is faintly marked by the 
arrangement of the <('I]s at that point. The optic disks are due to the rai)id multiplication of epi- 
blastic cells around delinite centers. Each is Joined to the ventral plate by a lateral band or cord 
of (sells (L. Cd.), on which the ajipendages are subsetjuently budded oft". A transverse cord (T. 
('d.) soon bridges over tlie space between the optic disks, thus inclosing a triangular area, whicth 
t;orresi)onds largely to the sternal region of the adult. The extension of the invaginate cells below 
the surface is only i)arlially indicated bj- the shaded nuclei. They advance forward and backward 
from the jioint of ingrowth, but principally upward, that is, toward the center of the o.gg, along 
the lines joining the ojitic disks to the ventral plate (Figs. 59, GO). The embryo covers nearly 
one hemisi)here of the egg. It is V-sbaped, but the angle between the arms of the V varies nnich 
in dittt'ient eggs. There is a marked contraction of the embryo which takes place immediately 
after this phase, that is, the area of the surface occupied by the embryo becomes aiii)reciably 
smaller. A similar contraction of the embryo has been observed in Astacus (54) ami Crangon (31 ). 
With the extension of the epidermis there has been a corresponding activity among the wajulering 
cells. Their relations are well shown by sections through the entire egg (Figs. 5G, 51), 60), in which 
we can still distinguish the jjrimary yolk cells (F. Y. C.) from the cells derived from the invagi- 
nation (S. Y. C). The cells of the first have large, granular nuclei and send out i)rocesses into 
the yolk. The others are smaller and are probably multiplying more rapidly. It soon becomes 
impossible to find any distinction between these wandering cells. The yolk is irregidarly seg- 
mented into balls (l''igs. (iO, (i3, Y. B.), inside of which the migrating cells are usually found. The 
epiblastic cells of the surface, which are the direct descendants of the yolk pyramids, have definite 
boundaries, but sonn^ of the cells of the ventral plate (PI. IX, Figs. 61, 63) tend to form a syn- 
cytium, as already seen, while the wandering cells are independent, free-moving elements. 

The lateral section (Fig. 56) passes through the outer edge of the ventral plate, and the 
next toward the middle line (Fig. 60) encounters a sheet of wandering cells. ' We see at a glance 
that the migrating colls pervade the greater part of the egg, and that they pass out in all direc- 
tions from the region of the ventral plate (Ab. P.). Fig. 59 represents a median longitudinal 
section through the embiyo and entire egg, and Fig. 63 a part of a .section highly magnified through 
the ventral jilate and region of ingrowth. The cells immediately below the surface (S. Y. (J.) 
are characterized by large and very granular nuclei, which stain with much less intensity than the 
sni)erficial cpiblast. This shows that they are multiplying rapidly, and the finely divided yolk in 
their neighborhood shows also that the cell ]irotoi)Iasm is rapidly absorbing food. A series of trans- 
verse sections of this embryo is given in PI. xxxiii. The phine of section in Fig. 61 is oblique and 
passes in a i)osterior direction. In Fig. 62 the lateral cords (L. Cd.) are crossed and numerous 
waiulering cells are encountered, while anterior to this (Figs. 68, 69) the optic disks are cut. The 
<i])tic disks (Figs. 64-(i7) (ronsist of a single layer of epiblast. Their cells are Hat and polygonal, 
cell bcuindaries are distinct, and the buig axis of the oval nucleus is parallel with the surface. 
When the cell divides this position is reversed, the plane of division being perpendicular to a 
tangent at the surface. From the optic disk the eye and its ganglia are developed. 

Stage IV. — Thickening of the optic disks and ritdimbnts of the appendages. 

An embryo a few hours older than the last described is shown in Fig. 72. On the thickened 
cords of cells (Ij. Cd.) uniting the ojitic, disks to the ventral ]>late the traces of two pairs of a])i>end- 
ages can be made out — tlie fii'st pair of antenna- A (I.), and, elo.se to the ventral plate, the mandibles 
(Md.). Some of the central cells (C. M.) of the optic disk have large, granular nuclei. These 
mark the area of most active cell division, and form an ingrowth or thickening, which is the rudi- 
ment of the o[itic ganglion. 

Glancing at a .series of longitudinal sections through this egg (Figs. 70-71, 73-75), we notice 
S. Mis. 94 26 



402 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

several important changes since the last stage. The ventral plate is more extensive and the 
wandering cells are more numerous. The primarj' and secondary wandering cells can no longer be 
distinguished, but all the cells within the yolk are similar in character. They have large, granu- 
lar nuclei, and multiply by ordinary karyokinesis (Fig. 75, Y. C^). Some pass forward underneath 
the embryo (Fig. 74, Y. C.) and to other parts of the egg. In Fig." 71 two yolk elements are 
found near the lateral cord, and in Fig. 70 one is seen just under the optic disk. lu Fig, 75 
the section is ruedian and corresponds closely with the similar longitudinal section of the last 
stage (Fig. 59.). The transverse cord (T. Cd.) is seen to consist of a single layer of flat epiblastic 
cells. 

The structure of the ventral plate is shown in detail in Fig. 85, which is a section just in 
front of the point of invagination. This illustrates the character of the syncytium beneath the 
surface of the plate and the fine degree of fragmentation which the yolk suflers in the presence 
of the cell protoplasm. At the surface, the cell walls are quite distinct, as already seen, but as 
soon as the cells pass below it, the protoplasm extends itself in pseudopodialike processes and 
incloses i)articles of yolk. Under these favorable conditions of nourishment these elements, which 
nuist he regarded as the mother cells of the mesoderm and the endoderm, multiply rapidly and 
spread to all i)arts of the egg. If this section is cotnpared with that of the invagiuate stage (Fig. 
54), and with a similar section of Stage in (Fig. 61), it is easj' to understand the relations of the 
ventral plate to the wandering cells, and the way in which the thickening of the plate is brought 
about. At the second stage comparatively few cells take part in the invagination, and the most 
of these pass directly into the yolk. But, almost simultaneously with this migration of cells there 
occurs a migration of cells from the surface of the ventral plate. Thus this becomes thickened 
and cells continue to be supplied to the yolk. This thickening of the plate is possibly due to cell 
division in both planes ; that is, to delamiuation and emigration. (Comjiare cells EC, EC'^, Fig. 85.) 

The process by which the optic disk becomes thickeued at this stage is quite similar, although 
there is no true invagination concerned in it. This is shown by a series of connective sections 
(Figs. 76-83) passing through the entire disk. The anterior rim of the disk is cut in Fig. 76, and in 
Fig. 83 the rudiment of the first antenna. This thickening is mainly the result of the migration of 
epiblastic cells from the surface. After leaving the surface, the cell wall usually becomes indefi- 
nite. The relations of the optic disks to the entire egg are seen in Fig. 84. The central yolk is 
segmented as shown in Fig. 74, and a yolk cell usually lies within the segment. 

Stage V. — Rudiments of three pairs of appendages — cell degeneration. 

The embryo represented in Fig. 93 is, approximately, three days old (temperature at Nassau 
78-80° F.). It occupies nearly one entire hemisphere of the egg, the opposite side of which is 
covered with flat epithelial cells like those seen at the periphery of the figure. The shape of the 
embryo proper is uearly that of an equilateral triangle, one angle of which corresponds to the 
ventral plate, and the other two to the optic disks. A line drawn through the first of these angles 
and the middle of the o])posite side would therefore correspond with the longitudinal median 
axis of the embryo. 

The rudiments of the second pair of antennje, A (II), have now appeared, and we therefore 
have present at this stage buds of three pairs of appendages, namely, the first and second pairs of 
autenuai and the mandibles. All are developed nearly simultaneously, but the second pair of 
antenniB seem to lag a little behind the rest. lu respect to the order of appearance of these 
appendages, allied species of Crustacea differ slightly. The central parts of the ventral plate 
( Ab. P.) and optic disks (C. M.) are areas of rapid cell division, and are characterized by the presence 
of large granular nuclei and by the irregular arrangement of the cells. In all other parts of the egg 
the superficial cells form a uniform stratum one cell deep. This irregularity is due to the gradual 
migration from the surface of individual cells in these three places. The first pair of antenute 
are closely associated with the optic disks, and the mandibles abut against the ventral plate on 
either side of the middle line. The appendages start on the lateral cords from definite centers of 
cell division, and the cells tend to assume a radial and concentric arrangement around each center. 

The space between the optic disks is now completely bridged over by a sheet of closely 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 403 

crowded cells (T. Cd.), and the backward extension of this, and tlio approximation of tlie lateral 
cords lias quite closed over tlie central or sternal region of this i)art of the eud>ryo (St. A.). Cell 
(lutliiies an- very distinct at the surface in preparations, and they are sometimes well defined in cells 
wiiich have passed from the surface to parts below it. in both tiie I'efiion of the optic disk and 
that of the ventral plate (Fig. SO, Ec), but elements closely associated with yolk are usually am<e- 
boid. The nucleus of the epiblastic or epithelial cell on the confines of the embryo, or on the extra- 
embryonic surface of the egg, has the shape of a flattened, round, or oval disk. Epiblastic nuclei 
in the appendages and other parts of the embryo, where there is rapid cell division, are angular 
in conseipience of crowding, and deep-lying nuclei are generally spherical. 

The arrangement of the embryonic cells of the superficial ei)iblast in beautiful curves and rings 
around dclinite centers — orthogonic systems of curves — is not nearly so pi'onoun(;cd as in theend)ryo 
crayfish (A.stiicitsjiiiviatilin), according to the delineations of lieiclienbach and Winter. Keichen- 
bach states that in the crayfish the 8ui»erficial embryonic cells multi[>ly about a given center, like 
that of the "head fold" (optic disk), or " thoracic abdominal rudiment," according to definite 
laws. This was discovered by Sachs in the growing tiiis of i>lants. According to S;u;hs, Iteich- 
enbach, and others, the cell nuclei always divide iu one of two opposite planes; that is, they either 
separate along a radius drawn from a given center, thus giving rise to radial strings of cells, 
or in a plane at light angles to this, producing new strings. Thus there is developc<l about the 
initial cell a series of concentric circles and radiating lines of cells. The positions of the equa- 
torial plates of dividing nuclei, which some eggs of Alpheus show in abundance, do not indicate 
the i)revalence of such a law iu the earlier stages. The early embryo of Alpheus is much less 
diffuse than iu the crayfish, and the difierent cell groups soon impinge on each other, and their 
relations are disturbed. 

Several transitional .stages between the last two embryos figured (Figs. 72 and 93) will now be 
examined. The first is represented by three longitudinal sections (PI. xxxvi. Figs. SS-UO), and is 
about seventy hours old. It is from the same jirawn as the segmented egg shown in PI. xxvii, Fig. 
!;■>. Tlie.se sections give some interesting facts with reference to the role of the wandering cells. 
TIk- first (Kii;. SS), which is nearly median, cuts the ventral plate and below it the cells which are 
migrating I'rom it into the yolk. A continuous layer of c^lls extends anteriorly to the transverse 
cord (T. C<1.). In this region a wandering, mesoblastic cell (Y. C.) is nearly in contact with the 
siiptTficial cpiblast. The next .section touches the outer edge of the ventral plate (Fig. 89), 
which is marked by large granular nuclei, and crosses the lateral cord and rudiments of the ap- 
peiida^jes ( A. I, A. II, Md.). The folds of the latter arise through the ingrowth of sai>erficial cells. 
Here another cell (Y. C) is close to the outer surface of embryo; another (Y. C.') is in a distant 
part of the egg and is in the aster stage of karyokinesis ; others still ( Y. C'.^) have w^andered iu a 
diametrically opposite direction. In Fig. 90 we see still more of these wandering cells, in this 
instance, chiefly above the embryo. 

In the middle of the optic disk some of the large granular cells visible from the surface (Fig. 
9.'i, CM.), are met with, and one of them (Fig. 90, Ec. dotted line extended) has Ju.stpa.ssed below it. 

Figs. SO and 87 are parts of longitudinal sections of an embryo six hours older than the last. 
The first exposes the optic disk (O. D.) and gives evidence of the further increase of the latter by 
the emigration of cells from the surface, and it is quite probable that .some of the wandering, meso- 
bhustic cells (Y. C.) have already attached themselves to it. (Conqiare Fig. 90.) In the next (Fig. 
87) the inner edge of the optic disk (O. D.) and the outer border of the ventral plate (Ab. P.) 
are involved. Here the ei)il)last consists for the most part of a single layer of cells. Two large 
wandering elements (Y. C) are in contact with the surface cells of the embryo in the neighbor- 
hood of the appendages. 

Fig. 91 is from an embryo twelve hours older than the last. The plane of .section pa.s.ses 
obliipiely through the optic disk, cutting the anterior half of one (to the left) and the posterior 
part of the other. A study of this section and of the series to which it belongs, shows iw beyond 
a doubt what is the fate of large numbers of wandering cells, [ire.sent at this time. -Vs has been 
already shown by preceding figures (see Figs. 73, 8S, and others), the cell mass constituting the 
thoracic-al)ilominal plate is now the principal source of the wandering yolk elements, and, as has 
been al.so shown, they migrate into all parts of the egg, multiply by karyokinesis, and settle 



404 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

U11011 the optic disks, the bases of the appendages, and other parts of the embryo. They also 
pass to the extra-embryonic surface of the egg. In Fig. 91 one of these wandering cells (Y. C.) 
is ajiproaching the surface, while another (Y. C) nearly touches it; and in PI. xxix, Fig. 34, 
which represents a portion of a section from a later series (Fig. 106) greatly enlarged, we lind 
two yolk elements (Y. C.) quite at the surface. They are triangular in outline, oue of the flat- 
tened sides being applied to the surface of the egg. Histologically their nuclei are more gran- 
ular and stain with less intensity than the nucleus of the ordinary epiblastic cell (Ep.), which 
appears spindle-shaped in vertical section. But between a cell like that seen in Fig. 91 (Y. C), 
where the long axis of the nucleus is at right angles to the surface, or cells like those shown in 
Fig. 34, where the nucleus is dattened against it and the ordinary epiblastic oell, a variety of tran- 
sitional phases can be found. TLis is most clearly illustrated in the next stage. 

The egg already described (Fig. 93) shows some important changes. The structure of the optic 
disks and ventral plate is readily seen in the transverse (Figs. 92, 94, 95) and lateral longitu- 
dinal sections (Figs. 96, 97). The optic disk, which in stage lir consisted of a single stratum of cells, 
(Fig. 69), is now a thick cell-mass two-thirds the size of the ventral plate. In it we still distin- 
"■iiish a small area of cells with large granular nuclei (Fig. 93, C. M.), which, as we see in Figs. 96, 97, 
C. M., O. D., is clearb' differentiated. It occupies a position just without (or external with respect 
to the longitudinal median axis) the center of the disk. The nuclei of surrounding cells are not 
more than half their size. These large cells do not all lie at the surface, but form a solid mass 
extending iuto.the yolk. The evidence of karyokinetic figures shows that these cells are dividing, 
and usually in planes perpendicular to the surface. This results in the crowding of the cells, and 
also in their migration from the surface to parts below it. 

In Fig. 90 there is a cell (ec.) whose nucleus has sunk below the level of the surrounding cells, 
but the cell protoplasm still reaches uiJ to the surface. Such cases render one cautious in pro- 
nouncing iiositively upon the emigration of cells, but sections like that given in Fig. 94, and the 
fact that cell divisions seem to be for the most part in one plane, convince me that the thickening 
is partly, if not largely, due to this cause. In Fig. 95, a large cell, the polar star of which is Just 
below the surface, is delaniinating. Cases of this kind were rarely noticed, but were observed at 
a later stage (PI. xxxix, Fig. 102, ec). That wandering cells attach themselves to the optic disk, 
there is little doubt. They can be traced in all stages of progress from the region of the ventral 
idate to the neighborhood of the disk (Fig. 90, Y. C.) until they fltially come in contact with it. 

The thickening of the optic disk described in Stage in (PI. xxxiii, Fig. 69), is therefore efl'ected: 
(1) partly, perhaps largely, by emigration of cells from the surface; (2) partly by delamiuation ; 
(3) by the accession of wandering cells; (4) by the indirect cell division of the elements constitut- 
ing the deeper part of the disk. 

Chromatin grains make their appearance somewhat abruptly at this stage (Fig. 96, S.'-.) and 
they serve to explain in some degree the peculiar granular nature of nuclei in earlier stages. They 
originate by the degeneration of cells in the ventral plate and in other jjarts of the embryo, and 
probably correspond to what Keichenbach has called in the crayfish " secondary mesoderm cells." 
Their history has been fully traced and will be discussed in Section vi. 

The structure of the ventral plate (Fig. 92) resembles that of an earlier stage (Fig. 85) with 
the difference that the nuclei are considerably larger and contain from one to several large s[)ore- 
like masses of chromatin. This cell mass has not inci'eased in bulk at a rate corresponding with 
the growth of other parts, since elements are being continually subtracted from it and added to 
the yolk. This loss on the part of the ventral plate is made good not only by cell divisions, 
but also by continued emigration from the surface (Fig. 9S, Ab.). 

An embryo six hours older than the last is represented by three longitudinal sections (Figs. 
98-100). The optic disks resemble in size and general shape the three pairs of rudimentary limbs. 
The abdominal fold is not yet formed and the labrum is undeveloped. The stomod:eum (Fig. 38, 
Std.) is jsfit making its appearance as a slight invagination of epiblast on the middle line between 
the first pair of anteuuic. The number of chromatin balls (S) and degenerating cells (S. C.) has 
greatly increased. We see them in all parts of the embryo. Sporelike nucleoli are seen in cells 
of the ei)iblast and are confined to no part of the embryo, but they are most characteristic of the 
ventral plate and optic disks. 



MEMOIKS OP THE NATIONAL ACADEMY OF SCIENCES. 405 

In Fig. 98 several independent cbromatin balls (S) are seen in the yolk, and the grannlar 
cells ol" t 111' ventral jilate are very marked. A large nucleus of one of the cells (ec), which contains 
several sporelike bodies, is very irregular in shape, owing to the pressure to which it is subjected, 
and it has evidently been crowded down from a level nearer the surface. The cell protoplasm, 
however, sliows that it still belongs to the surface tier of cells. This is also true of the small len- 
ticular nucleus next it on its anterior side. Just anterior to this cell is another (Ec.') which is in 
the act of dividing in the usual way. It seems probable that had this division been effected one 
or more of the adjacent cells must have been crowded quite below the surface. It is diflicult, 
however, to always determine whether cells whose nuclei are, a considerable distance below the 
surface do not send up stands of i>rotoi)lasm to meet it. We find in the ventral i)Iate, inde- 
pendent cells multiplying by karyokinesis, and, as evidences of delamination in this region are rare 
or altogether wanting, we are convinced that, as in the case of the optic disks, this tliiekening is 
largely due to the migration of (h^IIs from the surface. 

There is at this stage a fairly well-defiued sheet of cells (Figs. 9!l, 100, Mes.) extending forward 
from the ventral i)late on either side. The nuclei are oval or elongated, and their long axes are 
parallel with the surface, that is, at right a.ugles to the major axes of the superticial ei)iblast cells. 
This layer of cells is most marked at the bases of the a]>pendages (Fig. 100, Mes.) and extends 
from the optic disk on either side to the ventral plate. The question of the origin of these cells 
is not (lillicult. They are wandering cells which have settled down on these parts of the embryo. 
They form a part of the future mesoblastic tissues ; exactly what part they play will be discussed 
later on. They multiply by indirect division and extend into the folds of the appendages, while 
some, on the other hand, degenerate. 

Stage YI. — The eggnauplius. 

The fully developed eggnauplius is represented in Fig. Ill, but before this condition is reached 
tj^ere are several intermediate stages to be considered. A series of longitudiiiiil sections (PI. 
xxxix, Figs. 101-105) illustrates the structure of an embryo twelve and a half hours older than 
the one last <lescribed. The thoracic-abdominal fold (Fig. 104, Ab.) can now be recognized, and 
the stoiiioda'um (Fig. 10."), Sid.) has the form of a straight, narrow tube, between the buds of the 
first and second jiairs of antenna'. The space between these two structures is filleil with yolk 
fragments, among which are scattered, numerous chromatin particles (S) and cells derived from 
the tlioraeie-alxloniinal fold. The epiblast of the sternal region (Fig. 10.5, 98, St. A.) is no hniger 
a simjile layer, but, is slightly thickened. This thickening seems to be partly due to rapid cell 
division in one plane. The cell nuclei are elongated or wedge-shaped and stand perpendicular to 
the surface. As will be .seen later it is also due to the accession of wandering, mesoblastic (-ells. 

The stoinoda'um is a relatively long straight tube with very slight lumen, and is surrounded 
with chromatin grains and scattered cells. It is formed at a considerable distance in front of the 
])oiiit of invagination, and one to two days earlier than the i)roctoda'um. 

The thoracicabdomiiial fold seems to arise by the sinknig down of the epiblast along a defi- 
nite line. There is thus formed a narrow transverse pocket (Fig. 106, Ab. C), which is quite deep 
and perpendicular wiih the surface. Numerons cells continue to pass from the thoracic-abdom- 
inal fold to various parts of the embryo, and to join the sheets of cells (Fig. 10,?, Mes.) already 
mentioned. In l<'ig. 10;5 the four segments of the embryo are well shown. This section crosses 
the optic disc ((). (i.), the buds of the three appendages, and the e<lge of the thoracic-abdominal 
fold. The sheet of mesoblastic cells (Mes.) is most marked opposite the folds of the appendages. 

The optic disks are now large masses of cells united by a transverse cord which is thickened 
slightly on the middle Inie. In Fig. lOli, three cells are met in karyokinesis, one in the abdominal 
area and two side by side in the optic disks. The former exemplifies the common method of cell 
division, while the latter is a good example of the less common delamination. As has been already 
seen, karyokinetic figures of dividing cells are commonly met with in Alpheus at all stages, except- 
ing the species Alpheux minor, where the division is at first probablj' direct. I have seen nuclear 
figures at the yolk segmentation stat;e of Cranfion, also in ITippa, Poiifonia and Ilomnrus, ami Rei- 
chenbach found tiiem in abundance in Astacuv. Indirect cell division is undoubtedly the rule iu 



406 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

the tlevelopiug eggs of the Crustacea aud probably of all the Metazoa. Since we ofteu study only 
the rapidly achieved result, the jihases of luicleiir division may be easily missed. 

Fig. 106 is a median longitudinal section of an embryo preserved a few liours later than 
the last. This shows the thoracicabdoniinal fold aud cleft (Ab. Ab. C.) previously referred to. 
Tlie sternal area between the latter and the stomodiTum now lies next the egg shell, but soon 
changes its position (Fig. 125, St. A.), owing to the forward growth of the thoracic-abdominal fold. 
Tilt' labrum, here undeveloped, soon grows backward toward the latter, helping to bend the 
tesoi)hageal tube and probably slightly altering the position of the mouth (Fig. 125). 

The i)roctodiBum arises as a solid invagination of the epiblast, at a considerable distance behind 
the abdominid cleft (Fig. 106, Pd.), in a stage intermediate between the embryos represented by 
Figs. 105, 100. A transvei'se section through the point of invagination is shown in Fig. 126, Pd. 

The relation of the embryo to the rest of the egg can be seen in Fig. 108, which belongs to 
the same species as Fig. 100. Besides the shell, which is unnaturally distended, the egg is sur- 
rounded by a delicate embryonic membrane (Mb.). This membrane is secreted early by the super- 
ficial eiiiblast, as shown by the fact that it does not conform with the thoracic-abdominal fold. 

Wandering cells (Fig. 108, Y. C.) become gradually less abundant, but still continue to pass 
to the outer surface of the egg next tlie epiblast. The transition from the wandering, auireboid 
cell to the tinttened mesoblast cell, lying close to the surface, can be best followed at this stage. 

The fully developed egg nauplius (Fig. Ill) is about a week old. Embryos from the same 
prawn vary slightly in size and in the degree of development, and also in the general character of 
the cells. In some, the cells are larger and fewer in number, in others they are smaller and much 
more numerous. The embryo is usually at one pole of the oblong egg. That repre.sented in Fig. 
Ill is about one eightieth inch long, and if the entire end of the egg were .shown the drawing would 
be nearly twice as large. 

The relation of the embryo to the whole egg can be determined from Fig. 127, where the plane 
(/f section is through the long axis of the egg, but through the short axis of the embryo. In the 
course of development the egg increases ajjpreciably in size and also changes its shape, at first bein^ 
spherical, l)ut gradually becoming oblong. At this period the long axis of the embryo (using this 
term to apply to the more obvious embryonic tissues of the egg) is parallel with the short axis of 
the egg, while in the course of growth the embryo spreads over one side of the egg, until its long 
iixis coincides with that of the latter. 

The optic disks have become large oval nuisses of cells which project from the surface, and 
may now, for the first time, be appropriately called lohes. They represent the eye and eyestalk. 
Tli<^ blocks of cells (S. O. G.) in intimate relation with the optic lobes are the ganglia of the antenn;e, 
and represent a large part of the future brain. The ai)pendages are all simple, but a bud soon 
grows out from the irosterior sides of the second pair of antenuiii. 

The right antenna is already bifid near its tip. A little later it has the appearance shown in 
Figs. 109 and 110. Rudiments of the first pair of nnxxilhe (Mx. I.) are also present. The ganglia 
of the second pair of antennie are developed in close union with the ganglia of the antennules. 
Together they form the supra-a^sophageal ganglion or "br.ain." The stomodanun (Std.) appears 
from the surface as a distinct mass of cells extending behind the labrum (Lb.). 

The thoracic abdominal Iblil, at first vertical to the surface, bends up and grows forward 
toward the labrum, an<l a shallow groove which marks the median notch of the telson plate (Fig. 
110) is formed at its (extremity. The anus passes forward (backward in a morphological sense) 
from its dorsal position through the median notch until, at a considerably later period, it comes to 
lie on the ventral side of the fold near its apex. The mass of cells (H.) behind the atuis probably 
represents the heart. Near the mandibles and maxilhv, cells are seen with large granular nuclei. 
These arc cells which have migrated from the yolk to this part of the embryo. Nuclei of epithelial 
cells are sprinkled over the entire surftice of the egg, but increase in number as we approach the 
embryo. 

The section through the entire egg (Fig. 127) shows someof the general characteristics of the egg- 
nanplius. The thoracic abdominal fold is here cut on a level with the anus, aud lies in a wide shallow 
groove. The yolk is composed of irregular blocks, only a few of which are represented, and con- 
tains numerous wandering cells. Some of these (Y. C.^) are settling down on the ventral nervous 



MEMOIRS OF TIIK NATIONAL ACADP]MY OF SCIENCES. 407 

plate, while others (Y. C. Y. C) have wandered far and wide through the yolk. The embryo is 
raist'd considerably above the general surface of the egg and tl»o shell more closely invests 
the t'gg thiin shown in the drawing. The embryonic membrane is not represented. 

l''ig. 125 is a nearly median longitudinal section, and shows the relations of the thoracic-ab- 
donunal fold, the o'sophagus, and the ventral or sternal surface between them. The loose and 
irregular arrangement of cells immediately below the surface is most marked, and al.so the granu- 
lar nature of the nuclei which is such a constant character. Numerous degenerating cells (S. S. C.) 
are seen near the u'sophagus, and anuebiform cells can be traced from the tlioracic abdominal fold 
to the surface immediately behind it. 

The structure of this embryo is illustrated more completely by a sciries of transverse sections 
(Figs. 114-124), the first two of which (IM. Xi.i, Figs. 114, 11.5) traverse the optic lobes, and tlie 
third cats the brain. The central mass of large cells which was noticed iu the optjc disks can no 
longer be distinguished. Tlu^ lobe (O. L.) is composed of similar cells with granular nuclei, the 
superlicial tier being somewhat the larger and columnar. In the brain the central cells are smalU>r 
anil stain more intensely than those at the surface (Fig. 110, S. O. G.). Wandering cells (Y. C.) 
can be Iraijed in their passage from the yolk to the optic lobes, brain, ventral nervous plate, and 
other ])arts of the embryo. Between the lateral halves of the brain there is a shallow median fur- 
row (Fig. 116, M. F.). This is continued backward into the much broader and deeper depression iu 
which the convex ventral side of the abdomen fits (IM. xlii, M. F.). Tiie three following .sections 
(Figs. 1 17-119) jiass tlirough tliefflSophagus,and the ventral nerve thickening immediately belli ml it. 

About the tesophagus (Fig. 117, Std.) numerous chromatin balls (S., S. C.) are seen in the yolk, 
and a mass of cells (Mes.) is met with at the base of the ai)pendage and within its fold. These 
elements are derived from the wandering cells and must be regarded as niesoblast. The fold of the 
appendage (ionsists essentially of a single layer of cells. Tlio.se elements whi(!h enter it undoubt- 
edly go to form the musculature of the limb while the cells of somewhat similar appearance, which 
are derived from the ectoblast, represent the ganglia and nerves. On either side of the (esophagus 
the yolk has undergone iniportant physical and chemical changes. The yolk spheres or blocks 
are full of vacuoles aud have a corroded and granular appearance, while in contact with the 
embryonic cells there is a residue of small refractive granules. The.se vary considerably in size, 
and some of them stain lightly in ha'matoxylin and represent the last stages in the degeneration 
of chromatin. The eroded and altered yolk (A. Y. S.) is rciiresented in many of the; section.s. 
Between the lesophagus and bivses of the aiitenu* the yolk is absorbed, leaving a protoplasmic 
reticulum (Fig. 117, Ret.). 

In Fig. 118 the mass of cells representing the maiulibular ganglion (Md. G.) is sectioned, and 
in the following figure, the mandibles themselves (Fig. 110, Md.). Numerous cells, both in this 
and the following sections, are seen in the course of their migration frcun the yolk to Join the 
ventral nerve thickening. The latter, which is the rudiment of the nervous system, is at this 
stage scarcely thickened at all, on the middle line, below the level of the mandibles. Thus in Fig. 
121 the buds of the first maxillae (Mx. 1.) are unite<l by the primitive layer of epibla.st. To this a 
single migrating cell has attached itself on the middle line. Migrating me.soblast cells (Mes.) also 
pass into the fold of the ajjpendage, and others (Fig. 120, Mes.) take up a position against the 
epiblast of the body wall. The nuclei of the latter stain intensely and become flat, s])indle shape 
in section, and probably represent the nuclei of muscle cells. 

The structure of the abdomen at this stage is shown in Figs. ]20-12.'>. The body wall of the 
dorsal side consists of a single layer of columnar epiblast, while the ventral wall is thickened. 
The hind gut (Fig. 122, Hg.) is a tube, the wall of which con.sists of a single layer of cells. It is 
laterally compressed so that the lumen is hardly appreciable. The intervening cells (Mn.) largely 
represent the rudimentary tlexor and extensor muscles of the abdomen. A comparison of Figs. 
12;{ and 12.5 shows that cells extend from the thoracic-abdominal fold on all sides into the yolk. 

The cells at the surface in Fig. 124 have come mainly from the yolk (11.) and are in the i)osi- 
tion where the heart is subsequently developed. Cells approaching tlie surface in this region are 
very clearlj' shown in Fig. 125 (Y. C, Y. C), which is a section through a somewhat younger 
embryo. 

The wandering cells, as we have seen, abound in the parts of the yolk nearest the embryo. The 



408 MEMOIRS OF TOE NATIONAL ACADEMY OP SCIENCES. 

nuclei have the usual characteristics — irregular shape and granular contents. They are sur- 
rounded by a small irregular body of protoplasm which does not readily stain and which is often 
difiScult to observe. In Pl.xxix, Fig. 33, several of these wandering cells are seeu greatlj enlarged. 
Sometimes, as here, the perinuclear protoplasm appears to joiu that of neighboring cells, but in most 
cases there appears to be no such conuectiou between them. 

The endoderm, though not represented in the drawings, makes its appearance as a distinct cell 
layer at this time. In an embryo a few hours ohler than that represented in Fig. 125 the eudo- 
derm has the form of a narrow sheet of rather large cells, between the yolk and the rudimentary 
heart, near the body wall. In the space corresponding to the heart, blood corpuscles can already 
be detected, besides scattered mesoblastic cells. Both the latter and the entoblast are derived 
from the wandering cells which come out of the yolk. 

Stage VII. — Rudiments of seven pairs of appendages. 

Fig. 110 represents a phase intermediate between the egg-uauplias (Fig. Ill) and the present 
stage (Fig. 130), aud is of special interest for the light which it throws on the history of the wan- 
dering cells. The structure of this embryo is illustrated by PI. XLiv, and Figs. 13G, 137, 144, 145. 
Fig. 137, which represents a section just behind the base of the first antennai (A. 1.), may be com- 
pared with Fig. 117. Numerous yolk elements are found in the vicinity of the o'sophagus, where, 
as will be seen (Fig. 134, Mu.), they become speedily converted into muscle cells and somatic meso- 
blast. In Fig. 136 several wandering cells attached to the body wall, have all the characteristics 
of blood corpuscles, a deep staining granular nucleus, and a clear irregular cell body. The blood 
cell and muscle cell are both derived from wandering mesoblastic cells, and in the early stages of 
their metamorphosis they resemble each other, so that it is not always possible to distinguish 
them. Undoubted blood cells, however, have already made their appearance. 

Figs. 144, 145 show that the yolk is pervaded by a great number of cells. These originated in 
the way described, chiefly by migration from the ventral plate and thoracic-abdominal fold, aud 
also by subsequent multiplication in tiie yolk. At this period some of the cells migrate to the pole 
of the egg opposite the embryo and apparently assist in forming a conspicuous dorsal plate (Dp.). 
In this embryo they have not quite reached the surface. A structure is eventually formed which 
reminds one of the "dorsal organs" of various Crustacea. This and the wandering cells'will re- 
ceive further consideration later on. 

Tlie embryo of Stage VII is represented in Fig. 130, PI. xliv. Figs. Ill, 109, 110, and 130 
form a consecutive series of embryos, each but a few hours older than the preceding. In the first 
(Fig. Ill) the optic lobes, first aud second pair of autenufe, aud mandibles are all simple appen- 
dages, and are quite similar iu general appearance. The abdomen and part of the thorax are 
represented by a simple fold, the thoracic-abdominal fold. In the second embryo (Fig. 109) the 
parts are more compact and the second pair of antenna! are forked at their tips. In the third 
pha.se (Fig. 110) the optic lobes and abdomen exhibit the most rapid growth. The former are 
drawn closer together aud arch outward from the middle line. The anus is doi'sal. Tiie abdomen 
extends forward until it nearly meets the labrum and has a slight groove or depression at its ex- 
tremity. All the appendages have assumed a more oblique position with respect to the long axis 
of the body, aud the second antenuse are now the largest. 

In the fourth phase (Fig. 130) we see the same changes carried still further. The optic lobes 
are large convex disks which join each other on the middle line and are ntimately united to the 
brain. The anus is terminal. On at least the first pair of antenn;e hairs are developed, although 
there is not perhaps so marked a contrast between the first and second antennie in this respect as 
would appear from the figure. The first and secoud maxillfe and the first and second maxillipeds 
are present aa rudimentary buds. 

Tlie general structure of the embryo (Figs. 129, 131) agrees with that of preceding stage. 
The embryonic tissues consist of cells of various sizes and shapes, from quite large cells dowu to 
I)articles no larger than the balls of chromatin which are suspended within the nucleus, and from 
the spherical to the lens-shaped, spiudle-shaped,and wedge-shaped forms. Generally all the nuclei 
agree in containing coarse grains of chromatin or nucleoli. These vary much in size and number 
in different nuclei ac(M)rding to the condition of the cell. In degenerating nuclei, the chromatin 
residue is aggregated iuto fewer aud larger masses. 



MEMOIllS OF THE NATIONAL ACADEMY OF SCIENCES. 409 

Waiuloring cells are now scattered tliroughout the entire eprg. They occur in abiiiidiince both 
in proxiinily to tiie embryo itro[)er iuul on the sides of the body walls, and esjiecially in the region 
immediately behind the thoracic-abdominal fohl. 

l''i{j. I.jI is a. median longitinlinal section tlirongh an embryo liki^ that shown in Fig. 130. The 
outer or superlicial cells are generally columnar and have distinct boundaries. Their nuclei are 
si)herical, elongate, or wedge-ahajied. They divide in both planes, but most commonly in the 
)>lanc i)erpcndicnlar to the surface. When we compare this section with the similar one (Fig. 125) of 
the prece<ling stage the most striking difierence is the great increase in the length of the thoracic- 
abdominal fold and the ventral thickening of the nervous .system. Some of the cells of the latter 
next the yolk (Mes.) are tiattened and si)indleshaped. They have recently come from the yolk 
and. joined the nervous .system, and it is possible that these and similar cells represent primitive 
connective tissue envelopes. 

In a more lateral section (Fig. 129) the optic lobe is seen to consist of two portions, a super- 
ficial laj'er of large cells (O. E.) and a deeper layer (G. L.). The first is continuous with the 
general epiblast over the surface of the body. Its cells multiply in both [)lanes, and some of them 
pass below to join the deeper layer. The cells of the latter multiply by the usual mitosis and also 
receive accessions from the yolk. The plane of section passes through the equatorial plate of one 
of these dividingcells. Some of the cells next the yolk (Mes.) are flattened like those just described 
in the ventral nervous thickening, but this condition appears to be somewhat transitory. The 
outer layer of the optic lobe may be regarded as a retinogeu, since from it, or from a layer corre- 
sponilingto it, the visual ap|)aratus of the eye is developed, while from the deeper layer or (/aM<;/io(;cH 
the oi)tic ganglia of the eyestalk are formed. 

A comparison of the transverse sections (Figs. 128, 132-135) with corresponding sections of 
the i>revions stage (Figs. 115, 117, 121, 124) shows some interesting changes. The brain is larger 
and more compact, and .some of the cells next the 5 oik are flattened (Fig. 132, Mes.) and bear a 
resemblance to muscle or connective tissue cells. They originate from the cells marked Ct. S. in 
Fig. 110, and come from the yolk. Like the cells already mentioned in the optic lobes and ventral 
nervous system, they seem to represent a ruilimentary perineurium, but, as a well developed covering 
of the nervous system is not present until a considerably later stage, they are probably tran.sitory. 
Fig. 13-1 corresponds closely with Fig. 117. It shows the section of the (esophagus and of the 
ganglia of the second antenna;. In the younger stage the ganglion (seen to the left in Fig. 117, 
at the ba.se of the ap]iendage) is a small, loose mass of cells associated with the surface epiblast, 
while in the older embryo it is in contact with the wall of the oesophagus, is more compact, and its 
cells are .somewhat differentiated. The central nuclei are smaller and stain most intensely. The 
a'Soi)hagus (Sfd.) is suspended to the body walls by rudimentary muscles (Mn.), the cells of whicli 
are much elongated. They are derived from migrating mesoblastic cells like those seen in the 
earlier stage (Fig. 117, S. C), or like the one shown in this figure to the left of the a'sophagiis. 
Fig. i;{7, which is fiom a stage intermediate between the two just considered, gives addiiional 
evidence of this role of the wandering cells. Fig. 128 furnishes a very interesting comparison with 
Fig. 121. In the latter, cells abound in the yolk adjoining the rudiment of the ventral nervous 
.system, which is represented by the primitive epiblast on the middle line. In the older stage 
scattered mesoblast cells are greatly reduced in number and the ventral thickening is very 
marked. Cells of recent derivation from the yolk (Mes.) at the ba.se of the appendage can also be 
distinguished. 

In I'ig. 13 J, as in Fig. 124, the plane of section is just behind the thoracic-abdominal fold. 
Here we recognize a tier or i)late of tall, columnar cells (End.), the nuclei of which lie at the deeper 
ends of the cells or on the side away from the yolk. In the presence of these bodies the food yolk 
(I'^ig. 135, A. Y. S.) is ab.sorbed or converted into a granular residue. This layer represents the 
enUiUast or the epithelium of the mesenteron already described. Numerous wandering cells are 
encountered (Figs. 124, Mes. ; 135, Y. C), which take up a iieri])heral position, and from the first are 
closely asso(;iated with the epithelium of the hiiulgut. They unite the mesenteron to the hindgut, 
and it is imjwssible to say exactly where the one begins and the other ends. Between this ento. 
blastic j)latc and the surface e))iblast (Ect.) numerous <'ells are interpolated (l-'igs. 133, 1.35, Mes.), 
which are uiulonbtcd mesoblast. They arc directly continuous with the layer of mesoblast (Fig. 



410 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

128, Mu.) wliicb extends throughout the abdomen between the hindgut and body wall. Mesobhist 
cells derived from the yolk (Fig. 129. Mu.) are also seen underneath the epiblast ou either side 
of the body. The nuclei of these cells stain very deeply, and the cell protoplasm is prolonged 
into a short fiber or forms an irregular body. In the latter case the cells have the appearance of 
blood corpuscles. 

The heart originates in the mesoblast (Fig. 135, 7lfe.9.), between the entoblast and outer wall 
of the body, just behind the thoracic-abdominal flexure. 

At this time fibrous substance (punktsubstanz) is first seen in the brain. It appears as two 
small masses joined by a transverse commissure, in a plane just anterior to the roots of the first 
anteuniB. It is distinctly flhrous and apparently originates from the protoplasm of surrounding cells. 

Stage viii. — Segtmentation of the nervous system — at least eight pairs of appen- 
dages PRESENT. 

We have two longitudinal sections (Figs. 138, 139) to illustrate this stage. If we compare 
the latter figure with the corresponding one of the previous stage (Fig. 131) we see at a glance, 
that a long step forward has been taken in development. Between these, 1 have obtained cue 
intermediate phase, which is a trifle older than the embryo given in PI. XLiv, and can be best 
described by showing in what respects it differs from it. 

The rudiment from which the nervous system is formed (Stage vii) is a plate of cells extend- 
ing from the optic lobes to the apex of the abdomen. Anteriorly in the brain (Fig. 132) it is very 
thick, but gradually thins out as it is followed backward, until it consists of a single layer of epi- 
blast at the very ti]) of the abdomen. In the phase intermediate between Stages vii and viii the 
portion of nervous thickening between the oesophagus, which passes through it, and the thoracic- 
abdominal fold is partially segmented into cell masses, the primitive ganglia. 

The cells of this ectoblastic thickening may be roughly divided into a surface layer, the nuclei 
of which are large and contain difluse granules of chromatin, and a deep cell mass with smaller nuclei 
which stain more intensely. Similarly in the optic lobe we find a thick pad of uniform, deeply 
stained cells (gangliogen) next the yolk, and separated from this a well-marked surface layer (reti- 
uogeu) of larger ceils. The superficial, epiblastic cells on the inner or ventral side of the thoracic- 
abdominal fold are large and columnar. The nuclei are very much elongated and closely crowded 
together, and lie at all levels. This implies rapid cell division in this layer in a plane perpen- 
dicular to the surface, and as a result of this, the thickening of the ectoblastic plate in this region, 
such as we see in the next phase (Fig. 139). 

Near the apex of the abdomen there is a transverse zone of very large cells, and the smaller 
superficial cells adjoining it are arranged in parallel lines. Something resembling this was noticed 
in Stage VI (PI. XLii, Fig. 120, B. Z.). It corresponds to the budding zone (Knospungszone) which 
Reichenbach figures and describes in the crayfish. He detects it in a very early stage (Stage B, 
embryo with rudiments of the mandibles, corresponding nearly to Stage V of this paper), and finds 
that it consists of a transverse zone of cells containing large nuclei at the extremity of the abdo- 
men, below the notch of the telson. From it the segments following the mandibular segment are 
gradually budded off. 

TKe present stage is characterized by the segmentation of the nervous system and the great 
development of the optic lobes. The ventral nerve plate is blocked out by lateral constrictions 
into its component ganglia. There is also a median vertical ingrowth or constriction wliich tends to 
divide the plate into a double cord. It is, however, discontinuous at the middle of each block, so that 
the ventral nervous system consists of a double chain of ganglia, each p.iir of which are united by a 
transverse commissure or band of cells, and each ganglion is similarly joined to the one behind or 
in front of it. Distinct commissures pass from the brain aroniid the oesophagus and unite the 
former to the ventKil nerve chain. The first pair of post-oral ganglia contain two masses of fibrous 
substance united by transverse fibers as in the brain. The ganglia following these also contain 
punktsubstanz. It is developed as a small isolated mass on the dorsal side of each ganglion, 
toward the middle line. As development proceeds these masses increase in size and are grad- 
ually united by transverse commissures in each pair of ganglia (PI. xlvi, Figs. 150, 151, Fk.). 

A mass of fibrous or granular substance appears in ciich optic lobe in the gangliogen next the 
brain. Fibers pass from it to the punktsubstanz of ilie brain, which sends fibers down to the 



MEiMOlUS OF TUB NATIONAL ACADEMY OF SCIENCES. 411 

circam-OESophageal commissures to the first post-oral ganglia. The fibrous masses unite on either 
side of the ventral ciiaiii to form a double longitudinal commissure. Thus at an early stage the 
optic lobes, brain, and ventral nervous system are intimately connected by fibrous tissue. 

All the segments of the boily are now marked off as seen in Fig. 130. Tiie first jiost-oral 
segment is tiie maiidil)ular (g. iv), and following it are the segments of the maxillic the maxiili- 
peds and tiie first pereiopod. Tho second thoracic ganglion lies in the angle made by the 
thoracic-abdominal flexure. The third, fourth, and fifth thoracic, and the six abdominal segments 
constitute the thonicic-abdomiual fold. 

In the (superficial parts of the brain large elements are met with which multiply by mitosis, 
but have a distinct histological character. They consist of a large spherical nucleus containing a 
diffuse chromatin network, and a granular cell body without definite wall. They are the ganglion 
cells, wiiicli are abundant in all later stages. 

The optic lobe consists of two sliaii)ly distinguished parts already mentioned, the retinni and 
gangUnnic portions. The retinogen which forms tiie eye is a superficial disk of cells resting like a 
cap on the other part of the lobe, thickest on the outer side of the lobe and rapidly iliinning out 
toward the middle line to a single layer of cells. The nuclei are elongated and wedge siiaped, and 
cell division takes place commonly in a plane perpendicular to the surface, corresponding to the 
long axis of the vertical nucleus. The gangliogen consists of a deeper portion next the brain, 
containing a ball of fibrous tissue, and a part next the retinogen or eye rudiment. Below the thiirk- 
est portion of tlie eye the cells have large nuclei, which show a tendency to arrange themselves in 
rows radiating from the deeper half of the lobe. These large, clearer cells also extend down to 
the food yolk, and in lateral longitudinal .sections (Fig. 138) form the inner stratum of the lobe. 
The cells which lie between them and the eye, here one cell thick, are smaller and stain inlen.sely 
(v. Section ix). 

The heart (Fig. l.'i!), 77) is now a broad and greatly flatten* d chamber between the body wall 
and endoderm {End). It extends forward a considerable distance between the ejiiblast and yolk, 
and is continued backward into the superior abdominal artery {A. a. «.). It is tilled with serum 
and lilood corpuscles. 

The endoderm is a more conspicuous layer {End.), and the wandering cells are reduced in nnin- 
bers. They are still seen in all parts of the egg, approaching the body wall, the nervous system, 
the endoderm plate, and other parts of the embryo (Fig. 131), y. c). 

Stage IX. — Embryo with eye pigment forming. 

A sketch of the embryo at the time when eye pigment has already formed is shown in IM. 
XLVii, Fig. ir)S, The optic lobes are hnge pear-shaped masses meeting on the middle line iu 
front and arcliing outward and backward ou either side of the brain. The ocular pigment appears 
as a thin, dark-brown crescent near the outer surface of the lobe. Pigment is first formed at tho 
posterior end of the lobe nearest the base of the antenuules, and spreads upward over its larger 
convex eiul. The brain is constricted into two portions corresi)onding to the antennnlar and 
antennal segments. 

The segments of the abdomen are faintly marked ofif at the surface, and the telson plate which 
overlaps the month, is deeply forked at its extremity. (Compare with spatnlate telson of the first 
larva, PI, xxi, Fig. 9.) The plumose set;E which garnish the posterior edge of the telson are now 
represented by short stumps. 

The first pair of anteniKc are stout, simple appendages, tipped with setsp and folded backward 
along the sides of the body. The second pair of anteiinie Just inside of the latter, are biramons. 
They are also hairy at the tips, and the embryonic nieinbranes surround them like the fingers of 
a glove. 

The present stage is illustrated by Pis. XLVI and xlvii. Tlie drawings are made from different 
embryos, all of which are of the same age, excepting those represented by Figs. 152, 15s, 1.30, and 
l(il, which are a trifle more advanced. 

In the first series(lM. xi.vi. Figs. HG-l.Tl) the pigment cells are just forming in the eye. They 
are first developed iu the thickest part dl the retinogen next the food yolk. A single section, like 



412 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

Fig. 146, shows the complete history of development of the retinal layer from its one-celled con- 
dition toward the median line (already seen at an earlier stage, Fig. 136, Stage vii) to the point 
farthest from the middle line, where pigment is formed. The fibrous nerve tissue of the gan- 
liogen now consists of three masses, a ball nearest the brain, which is the first to appear, and two 
smaller masses between it and the retiuogen. Huge ganglion cells (go.) are of frequent occur- 
rence, especially at the surface of the eye stalk next the brain. (The details of the development 
of the eye are reserved for a special section.) 

The brain at this time (Figs. lid-l-iS) differs from that of the previous stage chiefly in point 
of size. It is composed of nerve cells and large ganglion cells {gc), which occur chiefly near the 
outer surface, and central fibrous tissue. It rests against the food yolk, and in the living embryo 
it is bathed with a current of blood (B. S.). The fibrous tissue of the brain has the form of a letter 
H with a wide and short transverse bar. In front of the transverse commissure (Fig. 147, Tc.) 
the fibrous substance is prolonged on either side into the optic lobes; behind, it extends down to 
the ventral nerve cord, on the inner side of the oesophageal ring (Fig. 148, ocm.). 

The ventral nervous system, like the brain, is bathed with blood, which fills a large sinus 
between it and the yolk. This communicates with extensive blood sinuses extending along the 
sides of the body (Figs. 148-154, B. S.). In some cases the food yolk, usually in an altered or finely 
divided state, is in close contact with the nerve chain (Fig. 157). Cells extremely flattened and 
spiiidlesliaped in section, are found in small numbers closely applied to the nervous system (Figs. 
152, 151, pr.), and forming a rudimentary perineurium. In most cases they are undoubtedly iso- 
lated cells, and do not constitute a membrane. They originate from the wandering cells and 
correspoinl to cells similar in shape and origin which appear between the yolk and nervous system 
at a much earlier period (Stage Vll, Fig. 131, jl/e.s.). The brain and ventral cord are not as yet 
differentiated from the superficial epiblast, but anteriorly, flattened epiblastic cells begin to appear 
between the nerve cells and cuticle. Ganglion cells (Fig. 150) also make their appearance in the ■ 
cord, commonly at either side, close to the surface. 

There is direct continuity of fibrous substance in the optic lobes, the brain, and the ventral cord 
as far back as the abdominal ganglia. In the latter this substance has not been develoi>ed. In each 
siugle ganglion there is a ball of this tissue wliicli is united to its fellow in the same segment by a 
transverse commissure (Fig. 151), and to the preceding and following ganglion by longitudinal com- 
missures. It is as a rule completely inclosed by the ganglion cells, but is separated from the yolk 
or blood sinus often by a unicellular layer (Fig. 150), and in the antenuular and antenual segments of 
the brain (Figs. 147, 148) the cells next tiie yolk are discontinuous. In the circumcesophageal cords 
the fibrous tissue also is without a cellular cortex on its inner or central side (Fig. 149,/s.). With 
slight changes these relations are maintained in the hatched larva (see PI., lv.. Figs. 220-2M2). 
The foregut is at this time a tube with definite walls and wide lumen (Figs. 148, 152, /(/.). At 
abour its middle it is bent abruptly backward on itsel£in an acute angle. The first portion, lead- 
ing from the mouth to the angle, is the oesophagus and is directed forward ; the hinder blind end of 
the tube lies in nearly a horizontal plane, and represents the masticatory stomach. The walls of 
the foregut consist of a single layer of columnar cells with large nuclei. They end abruptly next 
the yolk, but the cavity of the tube is screened from the latter by a thin membrane of flattened 
cells. A sheet of elongated or spindle-shaped cells surrounds the wall of the foregut and extends 
over the nervous system (Figs. 148, 149, Men.), while just below the oesophagus and behind the 
mouth a bundle of elongated cells grows over the nerve cords to the roots of the mandibles repre- 
senting the adductor muscles, which become so prominent in later stages. These relations are 
easily deciphered in the structure of an earlier embryo (Stage vii. Fig. 134), where we have already 
seen muscle and connective tissue elements, derived from the wandering cells, extending from 
the oesophagus to the epiblast of the body wall. 

Wandering cells also pass into the blood sinuses from all parts of the egg, and become 
converted into blood cells and connective tissue elements. In Fig. 148 we see two such cells on 
the edge of the blood stream, and in Fig. 152, (yv.) several of these bodies are in contact with 
the blood current on the side of the egg opposite the embryo. The relations of the epiblast, wan- 
dering cells and blood corpuscles in this part of the egg are seen in detail in Fig. 161, where a siugle 
large wandering cell is already half submerged in the blood. The various other drawings illus- 
trating this stage (Figs. 154, 155, 160, yc.) point to a similar fate for a portion of the wandering 



MEMOIRS OF THE NATIONAL AOADExMY OF SCIENCES. 413 

cells. This subject of the r61e of the wandering celliiiu Alpheus is one of the most difficult and 
at the same time the most interesting which has been met with m the study of its life history, 
and a full discnssion of it is reserved for another part of this jiajier (Section Vil). 

A new structure, the carapace (I'Mgs. I4.S-ir)l, IW), c/*.), is seen for the tirst time at this period. 
It takes the form of a lateral longitudinal outgrowth of ectoderm on either side of the body in the 
region of the thorax. These longitudinal folds represent the branohiostegites, which form tiie outer 
wall of the branchial cavity. In Fig. IGO the structure of the rudimentary carajiace and the way in 
which it originates is very clearlj' shown. The epiblast cells at the surface multiply and the cell 
juotoplasm is prolonged downward into long strands or spindles. Meantime the ectobiast is 
pushed outward along definite lines and the spindles of one side of this fold unite with those of 
the side opposite, thus forming a framework of transverse beams or pillars. Blood enters the 
fold, which thus becomes a respiratory organ. This structure is essentially maintained up to lar- 
val life (V. Fig. 195). 

The hindgut or intestine (Figs. 150, 157, Eg.) has a considerably larger lumen than in the i)re- 
ceding stage, but its histology is essentially the same. The walls are composed of a single tier of 
large columnar cells. The cell protoplasm is granular, and projects into the lumen of the tube, 
and the cell wall is usually distinct. There is an outer investment of mesoblast as in earlier 
stages, which is closely associated with tlie surrouuiling cells of the developing abdominal muscles 
(Figs. 150, ICO, mu.f.). The muscle tibre appears as an outgrowth of the cell protoplasm of the 
muscle cell. The nucleus elongates until it becomes rod-shaped. The fiber is homogeneous, 
nonstriated and stains feebly in borax carmine, but not at all in hsemotoxylon. The intestine com- 
municates with the midgut or the cavity which contains the great mass of food jolk, and with 
the exterior by the anus, which is on the under side of the tclson plate opposite the labrum. 

Fig. 157 shows the continuity of the epithelia of the hind and midguts, and illustrates in a very 
satisfactory manner the origin of the endoderm. Histologically the entoblastic cells resemble 
those of the adjoining epiblast, and it is impossible to draw a sharp line between them. The 
endo<lerm cells are vesiculated, have less definite boundaries, and extend pseudopodialike pro- 
ces.ses into the yolk. The endoderm begins near the point marked tuic. Fig. 157. Here the lumen 
of the tube eidarges, and the endoderm extends forward over the flexure of the nerve cord and 
upward over the sides of the body. Posteriorly it is separated from the body wall by the blood 
sinus which represents the heart and its arteries (H). The yolk next the endoderm is eroded and 
granulated. The formation of the endoderm thus begins near the abdominal flexure, in the egg- 
naujilius stage, at the point where the hindgut communicates with the cavity of the mesenteron, 
and advan(;es gradually forward on all sides. It is comjiosed of cells (Fig.157, y. <:) which migrate 
from the yolk and assume an extreme peripheral position with respect to it. They eventually 
acquire cell walls, unite and inclose the yolk which they continue to feed upon, ajiparently by first 
producing chemical changes in it and then absorbing its particles. In the early stages the 
mother cells of the endoderm and mesoderm can not be distinguished w ith certainty. However, 
since the endoderm originates as a distinct epithelial layer behind the ventral plate, and thence 
spreads forwards, slowly walling in the mesenteron, it is obvious that the bulk of the anteriorly 
wandering cells are mesoblast. 

The extensive blood sinuses which are now present have already been mentioned. In the 
angle between the optic lobes in front, there is a large blood space (Fig. 15-', b. s.), and blood 
passes from the heart upward and forward nearly around the egg in a thin irregular stream 
between the skin and food yolk. Mesoblast cells grow forward, from the abdominal region and 
line the outer sides of the endodermal wall, and exteiul u])ward to a thin .sheet between the yolk 
and the epiblast. Endodermal cells coming from the jolk attach themselves to this layer. The 
pulsatile chamber of the heart is not a very definite structure at this stage. It lies above the 
endoderm, nearly opposite the angle of the thoracic-abdominal fold. Its walls are delicate, and 
appear in sections as thin strands of mesoderm cells. The nuclei are elongated and the cell proto- 
plasm is produced into long processes. The pericardial space surrounding it is filled with blood. 

In Stage Vil (Figs. 144, 145, Dp.) we noticed an extraordinary migration of waiidtTiiig cells 
to the pole of the egg opposite the embryo. Tlie.se cells eventually reach the surface and rein- 
forcing the [Iiimitive ejjiblast, givt; rise to a conspicuous dorsal i)I.Tte, which is shown in l"ig. 153 
(Dp.). This is from an embryo intermediate between Stages viii and ix, in which eye-pigment 



414 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

is not yet formed. The plate is slightly thickeued at its center, where there is an iuconspicuous 
pit niarkiny the point of ingrowth. As the iuvagiuated cells pass into the yolk they degenerate, 
giving rise to spore like particles which spread in incredible numbers tlirongh a large part of the 
egg. Some of the wandering cells in this region doubtless degenerate before reaching the surface. 
A part of a similar section is shown in more detail in PI. v, Fig. 30. The i)articles vary consider- 
ably in size, stain uniformly and intensely and the yolk about them is granular or iinely divide<l. 
At a corresponding stage in the lobster (Homaru.s americanun), I have observed a large diffuse 
patch of cells which probably answers to the structurejust described. In this case the embryo rests 
ou the side of the oblong egg and the cell plate is at one end of it, at a point about 90"^ behind tiie 
embryo. This jiositiou seems to be quite constant, while in Alpheus the plate is nearly opposite 
the embryo, at the stage when it is most conspicuous. 

Stage X. — Embryo with eye-pigment strongly developed and the posterior lobes 

OF THE GASTRIC GLAND FORMING. 

All the thoracic limbs and the sixth [)air of abdominal appendages are present in a rudimentary 
condition. The abdomen has grown forward until the tip of the telsou now extends beyond the 
optic lobes. The embryonic telson is fringed with seven pairs of setse, and resembles the larval 
telson, except that the median notch is deeper. Seen from the exterior the eye-pigment has the 
form of an oval disk. 

The longitudinal section, PI. XLVili, Fig. 16S, shows most of the important changes which have 
occurred since the last stage. These chiefly concern the eye, the nervous system, and the midgut. 

The ectodermal pigment cells (retinular cells) of the retinogen have spread inward until they 
cover its whole inner convex surface (PI. xlviii, Fig. 107). Near the outer surface of the eye the 
crystalline cone mother cells («;) can be lecognized, and between the eye and the ganglia of the optic 
lobe there is a narrow space which communicates freely with the blood sinus (/>'. S.) on the outer side 
of the lobe. Wandering cells are frequently seen rear this blood sinus, and in the sp.ice between 
the eye and ganglia flattened cells also occur, which find their way in thither from the yolk. In 
the optic lobe another tibrous mass has ileveloped near the eye (Fig. l(>4-7). In horizontal section 
(PI. XLVii, Fig. 1.59) the relations of the tibrous tissue of the brain and optic lobes is clearly shown. 
In each lobe there is a chain of four tibrous masses united by a stalk of fibers to the anterior 
or optic swelling of the brain (of). 

The structure of the brain (Figs. 159, 169, 170) begins to apjiroach in coujplexity that of the 
larva, which was described in the first section of Part ii of this paper. The lateral fiber-balls, so 
cons|>icuous in the later stages have now appeared (Fig. 159 and PI. XLIX, Fig. 174, //'.). They are 
developed in close union with the large central tibrous mass, which su))plies the optic lobes, and 
probably belong primarily to the autennular segment. Beh)W this and nearer the middle line there 
is a less definite fibrous center (g/".) which supplies the autennal segment. With this, the oeso- 
phageal commissures are directly continuous (Figs. 171, 174 ovm.). 

The complete chain of ventral ganglia can be seen in Fig. 16s. This section is not jjerfectly 
median, but cuts a fiber-ball of each ganglion. The skin or hypodermis is now differentiated 
from the nerve elements and consists of a thin layer of flat cells. The fibrous masses of the gan- 
glionic chain are also imperfectly surrounded by jjeculiar cells, the nuclei of which aie spindle- 
shaped in section. These also occur in the brain, and in either case must be regarded as metamor- 
phosed ectoderm cells, or more probably as intrusive mesoblast. A transverse section of the nerve 
cord in the thoracic region is shown in Fig. 172, and corresponds very nearly in plane of section 
with Fig. 151 of the last stage. The fusion of the ganglia is now more complete, and the fibrous 
balls and commissure are relatively larger. (Compare with this. Fig. 176, a section of the thoracic 
ganglion of the larva.) In the abdominal ganglia the tibrous elements have essentially the same 
relations, but lie at a deeper level, being separated from the adjoining tissues by at most a single 
layer of nerve cells. In Fig. 168 we see that the yolk comes in close relations with the nerve 
cord behind the oesophagus to the endodermal fold (/) near the point of union of the iliesenteron 
and hindgut. Wandering cells approach the cord and become flattened against it, as already ob- 
served in much earlier stages. 



MISMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



415 



Tlit^ two <livi8ioii8 of tbe foregut, iesoi)hagus, ami masticatory stomach, have the relations 
alrea4ly (lescribed. The wall consists of a single layer of tall columnar cells. In Iht^ masticatory 
division tlie wall lias hegun to thicken next the yolk screen, its cells being cuneiform, and the 
nuclei elongated and crowded below the surface. From the anterior wall, muscle or couuective 
tissue cells extend forward under the braiu. 




niyi in 

Fic 1. — DiayriiiiiH iit" transverHO SfCtiona tbroagh the aliiiiontary irai-t of an enibrj'o of Alphcus tiaulci/i M-hiuli in 
nearly re;w!y Ut liatrli. to allow the origin of the ;j;a8lric ^land from the itostero hitei'ul lobes of tbe niiflt;iit. Si-ction 
I tuts thi' hiiiiljiiilaiiil lobta of the "liver," Section III tbe biml^ut wbeio it mrrues into the lueaeutelou. gij', gg', 
StrcoiHlaiy lobulertof iiig ' ; 110, hiiid<;nt ; mj', poatero-lateral lobea of loid^tit. 

The development of the meseuteron can be understood by reference to Figs. 102-1G5, IGtS, and 
185. The endoilermal e|)ithelium spreads by the division of its own cells and by accession of cells 
from the yt>lk, both forward over the nervous system and upward against the sides of the body. 
This is shown in the series of horizontal sections (Fig. l(i2-lC5). Fig. UJS which is from au 
embryo a little more advanced, shows that the endoderm is rising from the nervous cord near its 
point of llexiiie, into a transverse vertical fold. Simultaneously with the upward growth of this 
ventral foltl, two dorsal longitudinal folds grow downward, aiid-linally unite with the ventral fold 
antl with each other, thus coiistrictiug off from the alimentary tract two lateral pouches, the pri- 
iL-ary lobes of the " liver." The folils grow forward and the constriction i>roceeds gradually with 
the growth of the embryo. This process is illustrated by the diagrams (Fig. 1) which were drawn 
from an embryo near the point of hatching. The histology of the endoderm as shown in Fig. 173, 
is es.seiitially the same as in the previous stag^'. The cells are inismatic, and tlie nucleus .spherical, 
and, as in all stages, tilled with numerous nucleoli or chromatin balls. The cell walls are very 
delicate and the protoplasm often contains large vacuoles. 




9S> 

Fic;.'.>. — Seiiii<IiaKraniniatic representation of the alimentary i met and iin ;i|i|ien<la):ea in the 
lirat larva of Atiihrim taiilnii. The niidille lin^' of Ibe body i» also shown. F.S, foreRut . gg 1-3, 
secondary I obiili« of posliio lateral lobe of luidgnt; //S, hindgut; iiiy. uiidyul ; ing 1-3, an- 
terior, lateral, and post«ro-lateral divisions of luidgut; nio, mouth. 



41G MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

Wandering cells still occur in all parts of the yolk, tbough in far less abundance than in 
earlier stages. We find numbers of them moving toward the periphery, or next the body wall to 
take part in forming the endoderm. The epiblaist is conspicuous in Fig. 1G8 just in front of the 
optic lobes. This corresponds in position with the dorsal plate (Fig. 153 dj).), and is i)robably a 
remnant of it. The small clusters of cells beneath it and the degenerative products which occur 
near them, probably also represent the remains of the great swarm of degenerating chromatin 
particles which was formerly present in this region. A blood space (Fig. 1G8,) now extends over 
the dorsal side of the egg between the epiblast and the yolk, from the heart to the optic lobes and 
region of the head. 

Anteriorly we can distinguish in transverse section three vessels — a median impaired one, 
which answers to the ophthalmic artery, and a pair of lateral vessels, the antenuary arteries. 
The vascular walls are extremely delicate and contain flattened cells, the nuclei of which in longi- 
tudinal sections appear almost linear. Seen from the surface of the egg the blood vessels have- 
the appearance of two bands of tissue, passing backward from near the point of union of the 
optic lobes. Between and at either side of the optic lobes, and beneath and to each side of the 
brain, we find blood spaces packed with corpuscles (Figs. 100-109, B. iS.) It is not possible, in 
most cases, to distinguish at this phase true sinuses (veins) from arteries. The structure of the 
heart is shown in Figs. 164 and 1C8 (H.), and is essentially the same as in Stage ix« 

In Fig. 173 there is a small solid cluster of peculiar cells (R. 0.) on either side of the alimen- 
tary tract, between it and the heart. This I regard as the rudiment of the reproductive organ. 
The cells are clearly dift'erentiated from the surrounding cells. The nuclei are very large, spher- 
ical, and stain lightly and diffusely. They are enveloped in a capsule of mesoderm cells, like those 
forming the walls of the heart, and they originate from similar elements. In Stage ix (Fig. 157) 
these cell masses were first recognized. They are then distinct from the surrounding elements, 
and the nucleus contains a very delicate reticulum. Each cell cluster is so small that unless the 
sections are uniform and complete it is very easily overlooked. The muscles have developed in 
various i)arts of the body (Figs. 108, 171, 172, »«!<., mu. /., mu. e., (j. m. «.), but most striking at 
this stage are the great flexor and extensor muscles of the abdomen. 

The green gland (Fig. 170, A. G.) is another organ which we now meet with for the first time. 
It is an iiregular tube, closed at both ends, and lies at the base of the second antenna, extending 
up a short way between the body wall and brain. In the previous stage all the tissue at the root 
of this appendage is very loose and reticular, and no lumen can be seen. I have been unable to 
detect any opening of the gland to the exterior, nor should we expect to fiiul any, since, as we 
have already seen in Section i, there is none in the larva. It must be regarded as a mesodermic 
structure. 

Stage XI. — Embryo of alpheus heteroohelis nearly ready to hatch. 

The later stages (Stages vi-x) have had reference to a single species of Alpheus, namely, 
Alpheus mukiji, the larva of which is described in the first section. The embryo of Alpheus 
kcterochelis at about the time of hatching is considerably less advanced than the embryo of the 
first species at a similar period, and will serve in many respects as a convenient connecting link 
between the larva described in Section i and the last stage. The embryo of ^4//>/ie«s heterochelis is 
represented by a longitudinal vertical section and by a. series of transverse ones (FIs. l, li). The 
longitudinal sections of Stage X, of this stage, and of the larva (Figs. 108, ISO, 190), form a very 
interesting series for comparative study. 

The eye and the ganglia of the eye stalk (Figs. 177-179, 187) have become highly specialized, 
and closely resemble the adult organs. The brain is larger, but shows no new structures which 
have not already been noticed. The entire nervous system is more compact, and is completely 
separated from the skin. The foregut is larger than in the previous stage, and the walls 
of the masticatory stomach have become very much thickened. It is screened from the yolk 
by a membrane composed of large cells, which extend backward over the nerve cord. A double 
band of muscles (Figs. 108, 180, g. m. a.) passes upward from the anterior wall of the masticatory 
stomach and from the brain, to the body wall. These will be referred to the anterior gastric 
muscles. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 417 

The inesenteron {mg.) is very largely reduced in size and is filled with a granular coaguluni, 
and, anteriorly nest the head, with vesiculated and eroded reniiiants of yolk. The endoderni lines 
all but the anterior third of this cavity, extending farther forward on the dorsal wall. A few 
wandering cells are still present in the peripheral [)arts of the cavity next the advancing edge of the 
endoderni. Those elements, represented in Fig. 18:i, prove to he endoderm cells mechanically 
detachetl from the wall of the luesenteron. The i»riuiary lobes of the midgut ("liver") are larger 
but otherwise similar to those described in Stage x. The endoderni cells are greatly vesiculated, 
and the cell protoplasm has often a striated appearance. 

The heart (Figs. ISO, ISti, H.) has undergone \ery considerable changes since the period repre- 
sented by Pigs. 1G4, 168. It is no longer dorso ventral ly flattened, but in transverse section it is 
triangular in appearance. One side of the triangle is toward the intestine and one apex next the 
body wall. Irs suspension in the [lericardium is very delicate. The ectoderm cells send down 
spindle-shaped processes (Fig. 186), the Ectoderm p/eiler of Keicheubach, and to these, meso- 
dermal elements become attached. Tbe cavity of the heart is imperfectly divided by lateral 
partitions into three longitudinal compartments. In Fig. 186 the itartitions are imperfect and 
represented on each side by a single rudimentary muscle fiber. The walls and partitions of the 
heart are composed of delicate muscle fibers, which are distinctly striated. In the abdominal 
muscles, striations can also be made out. 

Stage XII. — The first larva. 

We now reach the stage with which this paper began, the first larva of Alpheus saulcyi. 
The histological structure of the zoiia in the species with a regular metamorphosis differs only in 
minor particulars from the larva already described. The organs are all very much smaller, an<l 
the cells are relatiNtjly larger and less compact. The meseuteron is about half tilled with the 
unaltered and unabsorbed food yolk. Wandering cells are almost entirely absent, and the eudo- 
dermal walls are nearly complete. The partition between the masticatory stomach and the midgut 
is absorbed and communication between them is established. 

The anterior and median lateral divisions of the midgut are present, but the posterior lateral 
lobes are represented only by spaces not as yet walled in by endoderm. There is a slight dorsal 
median fold of endodermal cells. In the larva of the same species three days' old the posterior 
lateral lobes are formed, but are very small. 

Stage XIII.— Alpheus ten days old. 

In the first twenty-four hours the larva moults twice, but the histological changes in this 
period are not of a very extensive character. The organs which experience the most rapid growth 
are the gills (I'l. liii. Fig. 195.). These have now acquired the folds or plates for increasing the 
respiratory surface, and are more eHicient as breathing organs. 

The fibrous tissue of the brain is relatively greater in bulk, and the tracts of fibers are more 
numerous and more complicated. The eye stalks are much shorter, and the ojitic ganglia and 
anterior parts of the brain are drawn closer together. 

In a larva four days old (PI. xxi, Fig. 3) the eyes are completely covered by the carapace. 
The ganglia of the eye stalks and brain are intimately fused together. The nervous system and 
all the tissues have undergone greater or less histological changes. These can be more conven- 
iently considered in a still older larva. 

The period of metamorphosis, strictly speaking, is passed in about twenty-four hours alter 
the time of hatching. The structure of an Aljtheus ten days old, which had spent its entire life 
in an aquarium will now be briefly considered. It is sexually immature and some of the organs, 
like the "liver" and green gland, are less complicated, but otherwise the structure is essentially 
that of the adult form. 

When we compare the brain of the first larva with that of the ten days old and the adult 
fully grown form, we find the same parts present in all. In the last two the fibrous tissue is rela- 
tively much greater in bulk, and ditlerentiation of the fibers and fibrous tracts has advanced much 
farther. The brain consists of the same fibrous masses surrounded with a thinner cortex of nerve 
and ganglion cells. 

S. Mis. 94 27 



418 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

The anterior or optic eulargement is coatinuous on each side with the ganglia of the eye stalks. 
Its two halves are united by transverse libers. The lateral enlargement is markedly kidney shaped, 
and from its hilus there issues a complex system of libers. A great part of these libers issue from 
the ganglion cells inclosing the lateral ball, pass out in a bundle to the middle of the brain, 
and thence up to the optic ganglia, appareutly without crossing. The fibrous substance of the 
lateral enlargement has a pyramidal structure — that is, its tissue is permeated with pyramidal blocks 
of a denser substance which stains faintly with carmine. The apices of these pyramids point 
toward the center of the ball. Below the lateral eulargement and nearer the middle line there is 
the antennular mass from which the auditory nerve issues. This is bilobed and has the same gen- 
eral relations as in the first larva (PI. lv, Fig. 216, //.). The antennal enlargement, which is 
closely connected with the latter, is now a much more conspicuous mass than in the earlier stage. 
From it issue the anteuual nerve and the oesophageal commissures. 

The alimentary tract has undergone very important changes, of which mention was made in 
Section i. What corresponds to the foregut of the larva comprises that portion of the tract from 
the mouth to the duct of the gastric glands. It is divisible into a straight and vertical portion, 
the (esophagus proper and a masticatory stomach. The latter consists of two parts, an anterior 
section continuous with the cesophagus, and probably corresponding with the gastric mill, 
and a pyloric portion or strainer. In transverse section the cardiac section appears circu- 
lar and the walls are rather thin and slightly folded. As this passes into the pyloric division the floor 
of the tract rises into a broad tongue-shaped process, which is surmounted by a particular strainer 
of hairs. This median fold is continuous throughout the pjioric division, where it narrows into a 
crest.' The lateral walls, which are greatly thickened and studded with hairs, approach each other 
so that only a small lumen is left, through which the food is strained as it passes over the net- 
work of hairs. These two sections of the stomach correspond to portions of the tract marked Ms., 
Fig. 196. They are of epiblastic origin, and in passing to the midgut the epithelium suddenly 
changes as it does in the larva. 

The ducts of the three glands unite on each side and thus form two common ducts. The 
epithelia of the gastric cwca of the ducts and midgut are directly continuous and pass gradually 
into each other. They consist of a delicate layer of connective tissue which forms a capsular in- 
vestment and the large columnar cells already described. In the " liver" many of these cells are 
in the process of active secretion, and as a result of this activity the lumen of the gland is filled 
with a coagulated liquid. The secreting cell at this period swells out to two or three times its 
former size and has the form of a distended bladder projecting into the cavity of the gland. The 
contents of the cell consist of a light granular fluid and when the cell breaks down this is dis- 
charged into the lumen of the gland. 

Just how much of the wall of the alimentarj' tract behind the glandular ducts is of endoder- 
mic origin it is impossible to say, since from the first there is no sharp morphological boundary 
betwfeen the hindgut and mesenterou. But it is certain that only a very small portion of it can 
arise in this way, and that the endoderm of the larva goes mainly, if not exclusively, to form the 
lining of the gastric cseca. 

The heart is very much compressed from above downward as in the adult. The walls of blood 
vessels consist of a single layer of cells which secrete a homogeneous limiting membrane. As 
in the early larva, the heart and pericardium are screened from the digestive tract and other organs 
by a horizontal membrane. The reproductive organs are still in the rudimentary condition 
already described. 

V. — NOTES ON THE SEGMENTATION OF CRUSTACEA.* 

Under this head I will add a few notes upon the segmentation of the egg of a number of 
Decapods, which have been studied chiefly for the sake of comparison with Alpheus. 

Alpheus saulcyi and A. heterochelis are both typical examples of centrolecithal segmentation 
with the formation of yolk pyramids. They possess a massive food yolk and hatch as mysislike 

* The concluding sections of this memoir were written after the lapse of a long interval, during which time it was 
not possible to refer to my earlier manuscript. This will account for any unnecessary reiteration of facts, or for any 
incousisteucies in statement which I have failed to eliminate. 



MEMOIRS OF TOE NATIONAL ACADEMY OF SCIENCES. 419 

larviB. On the other hainl, the Bahaiiiuii variety of Alpheus heteroclwlis ami Alplieiin minor (fioin 
Heaufort, North Carolina) ajjiee iti havinj; a n-latlvciy smaller yolk ami in hatching as z(ea-liko 
forms. Tlu-y diHcr, however, in their segmentation, the lirst species agreeing in this respect with 
A. sautcifi, while in A. minor yolk ^ly raniids are generally absent aird the segmentation is irregular. 
The yolk in A.ltftcrurhclin of Heaulort is ahout nine tiiiu'.s as volniuinons as that of the Hahaman 
heterochelis. The .segmentation, however, has remained unaltered. The i)eculiarities which we 
find in the early stages of .1. minor can not therefore he laid to the door of the yolk alone, but must 
be regarded as a comparatively recent modilication of the yolk pyramid type. Wliilt^ the type of 
segmentation may be very persistent and uniform, it is subject to piolbund change, not only in 
eloselj' allied species, but, as has been shown in a few instances, within the species itself. 

In the Decapod egg we have, as a result of uegmentation, a great central yolk-mass which is 
either undivided or imperfectly ilivided, ami which eom[>letely tills and obliterates the segmenta- 
tion cavity, and a surrounding layer of cells, the blastoderm. More fully stated the proce.ss is as 
follows : The segmentation nucleus divides first at a point near the center of the egg. The daugh- 
ter cells separate widely, and a second division follows. With subsequent divisions the cells 
ai)proaeh nearer the surface. The yolk may share in these early divisions but often does not, until 
eight or sixteen cells are formed (third or fourth segmentation stage). When there is no pro- 
gressive segmentation of the yolk in the early phases, the yolk segments appear either gradually 
and on one side of the egg, or make their appearance simultaneously in relation to all the nuclei 
present. Segmentation is always rythmical. During one phase (iieriod of "rest") the segnfents 
shrink away from the surface and flatten out in the usual way, while at the beginning of the period 
which follows (period of "activity") they swell and stand out prominently. The division of the 
yolk often appears total iu surface views, while in reality it is not. The constrictions marking 
off the segments may be nearly superficial, or they may extend deep into the yolk. Cell division 
is usually indirect. The only exception to this rule which I have observed is Alphciix minor (see 
p. 397). With each division the protoplasm approaches nearer the surface of the egg, and the 
segments become more pyramidal in shape. These are the "yolk pyramids" which were first 
described in the crayfish by Rathke in 1829. The bases of the pyramids form the surface of the 
egg and their apices fuse in the central yolk mass. The nucleus, surrounded by a rayed body of 
protoplasm, lies near the base. By repeated division the pyramids become smaller; the cleavage 
planes of adjoining segments become less distinct and the protoplasm draws nearer and nearer the 
surface. Before, however, any of the protoplasm is flush with the surface, certain of the cells 
divide horizontally, that is delaminate, and one of the products of each division migrates into the 
yolk below. The surface of the egg is now covered with a single layer of small polygonal cells, 
and the i)yramidal structure of the jieripheral yolk has nearly disappeared. The greater part 
of the protoplasm of the egg is thus at the extreme outer ends of the reduced yolk pyramids, while 
the lesser body of it is represented by the migrating yolk cells. 

The invagination stage soon follows, and the large numbers of cells which now become migra- 
tory (in Alpheus i)enetrating to all parts of the egg). Joining the primary yolk cells, represent 
mesoblast and entoblast. The process above described will be found to apply, I believe, to the 
majority, if not to all Decapods. Differences in detail may be expected in the time of appearance 
of yolk segmentation and the degree to which this is carried. This account differs from that usually 
given in recognizing delamination, following close upon the latter phases of segmentation, or the 
origin of cells, from the blastosphere before the invagination appears. This regularly occurring in 
such typical forms as Alpheus and Uoraarus argues strongly for its presence in allied species 
where it has possibly been overlooked. 

Stenopun Itispidus. — I have described and figured thesegmenUition of Stenopus in a paper on the 
life history of this form. In one egg which I sectioned before the beginning of yolk segmentation, a 
single cell, i)robably the male ])ronucleus, is seen at the surface, while another cell, the female pro- 
nucleus, lies near the center. A single polar body was also present, just beneath the shell, near 
the first nucleus. I saw no evidence of yolk segmentation until the third phase of division was 
reached. The yolk then be(;ame constricted at the surface into eight blastomeres. The superficial 
furrows are (juite (h-ep during active i)eriods, giving to the egg the appearance of total cleavage. 
This egg now resembles that of Peuieus as figured by Uaeckel, but iu the latter form yolk segments 



420 MExMOmS OF THE NATIONAL ACADEMY OF SCIENCES. 

appear at an earlier phase. The cleavage of the yolk is wholly, or almost wholly, confined to the 
surface furrows, dividing planes rarely extending into the yolk below. My material was not ade- 
quate for determining whether invagination was preceded by delamination or not, but seems to 
render it highly probable that a delamination does not occur. 

My observations on Pontonia domeKtica, Palwmonetes vulgaris, and Hippa talpoides are very 
fragmentary. In Pontonia 1 have one stage (Fig. 27) with three cells, one of which is dividing 
with no sign of yolk division, and another with sixteen nuclei and corresponding yolk 
pyramids. Here the conditions are precisely like those in Alpheus saulcyi at a similar stage, 
and probably the segmentation of the two is similiar. In Palamonetes Faxon ( 17 ), relying 
wholly upon surface views, states that segmentation of the egg begins in two planes almost 
simultaneously. These planes arc at right angles to each other and pass through the long and 
short axes of the egg. Whether this follows close upon the first division of the nucleus I have 
not determined. I have an egg with two nuclei near the center of the undivided yolk, and a stage 
with thirty-two yolk pyramids. This egg also agrees closely with that of Alpheus saulcyi at the 
same stage. The nuclei are not quite at the extreme surface of the yolk. In the next phase when 
sixty-four pyramids are present the protoplasm abuts on the surface (Fig. 24) of the egg. All the 
protoplasm is distributed to the yolk pyramids and no delamination has taken place. 

With reference to Hippa I can only add the note that yolk pyramids normally occur, and in 
the 64-cell stage (Figs. 1, 4) the lines of cleavage between adjacent segments are very distinct and 
extend nearly to the center of the egg. At this stage all the protoplasm is ajjparently concen- 
trated in these cells. Yolk pyramids similar in surface views to those of Hippa occur in CalUnectes 
hastatus, Platyonychus ocellatus, and Lihinia canalicidata. 

Crangon vulgaris. — Kingsley (31) describes the segmentation of Crangon as follows: 

With the first segnietitation the protoplasm begins to leave its central position and seek the surface of the egg; 
before the secouil division is completed it has reached the surface, leaving the yolk in the center. ♦ » * After the 
second protoplasmic segnieutatiou is eflected the first segmentation furrows ajipear, the one following close upon the 
other. The iirst to apjiear corresponds in its direction to the first nuclear division ; the second is at right angles to 
it. * * * In Crangon, so far as I have been able to see, amoeboid cells reach the surface and take i)art in the 
formation of the blastoderm before the process of gastrulation begins. In that form no yolk pyramids occur. 

Of cell division he says : 

In the process of cell division I h.ave never seen any traces of karyokinesis ; the division seems to be direct, and 
affects first the nucleus and next the protoplasm. • » * In fact I do not recall a single statement of karyokinesis 
being witnessed in decapod segmentation excepting in Astacus. 

On PI. I he gives a drawing (Fig. 3) of an egg with "about sixteen segmentation spheres." 
Fig. 4 of the same plate represents a section of the egg shown in Fig. 3 and has six nuclei, five of 
which are even with the surface, while one is near the center of the egg. The yolk sjiherules appear 
to be fused, owing possibly to the disturbing eft'ect of the reagents employed. This central cell, 
according to Kingsley, represents a portion of the egg protoplasm which is belated in its passage 
to the suiface, but it divides and gives rise to cells which eventually reach the surface at a certain 
point which marks the germinal area. Thus all the nuclei take part in the formation of the blasto- 
derm, and the migration of the belated cells is completed before the "gastrula" invagination 
occurs. I have made no observations on the very earliest phases of segmentation of Crangon, but I 
have several eggs sectioned at the sixteen-cell stage, which ought therefore to correspond with 
Fig. 4 of Kingsley's paper, but, on the contrary, they show a somewhat difl'ereut condition of 
things. There are just sixteen nuclei present, all of which are peripheral or nearly so, and each 
nucleus forms the center of a yolk pyramid, the cleavage planes of which are very marked and 
extend more than half way to the center of the egg. Fig. 15, PI. xxvii, of the segmented egg ot 
Alpheus, although belonging to a later phase, will fairly represent the condition of things which 
we find in Crangon. None of the nuclei are tangent to the surface, but between them and the sur- 
face there is still a considerable layer of yolk. Each is surrounded by a large mass of protoplasm, 
which stains lightly with hajmotoxylon, and has the characteristic rayed appccarance. One of tiiese 
nuclei is in the equatorial plate or metakinetic stage of division, and maybe represented very 
nearly by Fig. 28, which shows a dividing cell in the egg of Alpheus at the same jieriod. As already 
stated, the central yolk mass does not contain a single nucleus. The yolk is in the usual form of 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 421 

large spbernles ou angular blocks, wliicb are abundantly perforated with round lacunaB. Crangou 
agrees essentially at this stage with at least three other species, namely, with Alpheus saulcyi, 
Pontonia domestica, and Steitoi>us hispidits. 

It is probable that Figs. .3 and 4 ol Kingsley's paper do not correspond, the latter representing 
the older egg, that is, older than the sixtcen-cell stage. In the segmenting eggs of Homarus there 
is a striking individual variation, which finds expression chiefly in the external characters of seg- 
mentation, but 1 have never observed this in any related forniR, and can not say to what extent it 
occurs. Jiulging from analogy, I think it will be found that as a rule all the protoplasm in the egg 
of Crmif/oH TuUjaris reaches, or very nearly reaches, the surface, as in Homnrus and Alphciis snulcyi, 
and that toward the ch»se of the yolk-])yrainid stage dclamination 0(;curs and some of it wanders 
back into the depths of the yolk. If this is true, the "belated" cell near the center of I'ig. 4 of 
Kingsley's i)aper may represent some of the jirotoplasm which has taken this roundabout. journey. 

(While this memoir was in press a paper has appeared by W. F. K. Weklon, on "The Forma- 
tion of the (ierm layers in Orangon vulgaris." {Quart. Jour. Mir. iS'ci., Vol. xxxiir, ])t. .'i, March, 
1S92). Lie makes no mention of the biulding of cells from the blastoderm before invagination, 
nor of the presence of migrating cells at a later period not derived from the invaginate cells or 
ventral plate, hence it is probable that in Crangon primary yolk cells do not occur. In this case 
the suggestion just ottered does not let us out of the difhculty.] I have not succeeded in obtaining 
the segmenting eggs of Callianassa for comparison with the early stages of CaUianasna mediterranea, 
described by Mereschkowski (40). It seems to me, however, that the diagrams in Mercschkow- 
ski's paper are misleading, and that the process of segnu'utation in Calliana.ssa, instead of being 
peculiar as one might infer, is essentially typical. According to this observer's account the "blas- 
toderm" ari.ses without yolk segmentation. Nuclear division is at first central, and the resulting 
cells, sixteen in luimber, pass gradually to the surface and form a deep layer of |irotoplasm 
inclosing the yolk. This lajer, at tirst raised into hillocks corresponding to the nuclei, tinally seg- 
ments into sixteen parts around the latter. These segments are formed simultaneously over the 
egg, but the yolk is not involved. The cells multiply rapidly and form a layer of tall prismatic 
elements, which gradually flatten out as division proceed.s, into ordinary blastoderm cells. 

If there is any analogy between this egg and that of related forms the broad "protoplasmic" 
layer is really the protoplasm plus the i)eripheral yolk. It would be remarkable in any case if 
a segmenting egg could accjuire such a mass of proto])lasni, not to speak of the suddenness with 
which the accjuisition is nuide. That this layer, comprising more than one-half the contents ot the 
egg, is largely yolk is indicated by the fact that the nuclei which occur in it are representt>d as 
surrounded by a protoplasmic reticulum as normally occurs. If this is true, the j>cis»in/ic cells are 
yolli pyrainiih, and their line of separation from the central yolk is purely imagiuarj'. 

Ishikawa found, in his studies upon a Japanese prawn, Atyephyra compreiisa (27), that the egg 
underwent at first a total and regular segmentation. At the end of the fourth phase the yolk is 
centralized and the protoplasm surrounds it, and in the next stage, after thirty two blastomeres 
have been formed, the central end of each separates ofi' to form a yolk segment. The yolk .seg- 
ments, which till the center of the egg and correspond to the common yolk mass with whic^li the 
apices of the yolk pyramids blend in other Decapods, are of unequal size and contain nuclei which 
do not take part in the "blastoderm." These nuclei probably correspond to the delaminated cells 
of Homarus and Alphens. In the latter they appear at the close of segmentation. Ft is (juite 
probable that the time at which these cells are budded ofi' may vary considerably in different 
species. 

In Extpagurnn pridcauxii (39) Mayer found that the protoplasm .segmented tirst in the center 
of the egg, as in other forms, until eight nuclei were present. When this stage is reat^hed the yolk 
now .segments not simultaneously into eight blastomeres, as in the ca.se with the Isojiod Asrllus 
aquaticm, but according to its inherited primitive manner, first into two, then into four and eight 
spherules. Segmentation of the yolk is thus at first total, but after the fourth pha.se the s])heres 
unite in a central yolk core as in other forms. 

In Alphens saulcyi I did not find any eggs which showed a progressive segmentation of the 
yolk between tlwe stages represented in Figs. 9 and 10, and hence I infer, as already stated, that 
the segmeutAtion of the yolk is (here a simultaneous process for each of the sixteen segments 



422 MEMOIRS OP THE NATIONAL ACADEMY OF SCIENCES. 

involved. This remark also applies to Stenopns, where eight blastomeres or yolk pyramids appear 
at the beginniug of the third phase. In Homarus there is less uniformity in the appearance of the 
superficial segments, since the cells do not migrate to all parts of the surface at a uniform rate. 

Lereboullet (36) described the early stages of the segmenting egg of the crayfish Astactis 
fluviatilis in 1862. His account, though somewhat vague and unsatisfactory owing to the tech- 
lucal difficulties under which he labored, is confirmed in essential particulars by a later observer, 
Skimkewitch (56), who has given a short description, without figures, of the process in the Eussian 
crayfish AstacMS leptodaciylus. His account is briefly as follows: The cleavage nucleus with its 
protoplasm passes from the center to the surface of the egg and undergoes segmentation. The 
resulting nuclei, the exact number of which is not given, then diffuse over the surface of the egg 
and the yolk segments around them. The cleavage planes between adjacent pyramids, at first 
extend only half way to the center of the egg and never quite reach it. There remains at the close 
of the segmentation a small mass of undivided yolk (" dotierlcern^') lying in the center of the ovum. 

According to these observations then, Astacus offers us an example of centrolecithal segmen- 
tation in the most exact sense of the term. It seems to me quite probable that this migration of 
the protoplasm may be only apparent, and that the segmentation may proceed much as it does in 
the lobster. 

Brooks, in his memoir on Lucifer (8), gives an account of a segmentation which differs in 
some particulars from that of any macrouran which has been studied. The Lucifer egg undergoes a 
total and perfectly regular segmentation, and in the first stages may be compared with Eupagurus. 
In Lucifer, however, a segmentation cavity is formed, which can be clearly seen when sixteen 
spherules are present. At this time one pole of the egg becomes flattened, and one of the spherules 
in the area, which has become differentiated by the possession of food yolk, is gradually invagi- 
nated into the segmentation cavity. Meantime the invaginated cell divides; other changes ensue 
which lead to the infolding of more cells and the formation of a two-layered embryo, the "gastrula." . 
Brooks thinks that th<3 yolii bearing cell represents a yolk pyramid, and that after a longitudinal 
division each half divides transversely or delaminates, and that the other two inner cells contain the 
yolk, while the outer products remain at the surface and form a part of the "blastoderm" (or eudo- 
derniic invagination). This last point, however, was not settled. In Brooks's view the segmenta- 
tion in Lucifer is a secondary modification of the yolk pyramid type, and this has been brought about 
"by the gradual reduction of the amount of food material and its restriction, at last, to a single 
one of the cells of the segmenting egg." He says that, while Lucifer is undoubtedly a very primi- 
tive Malacostracan, it can hardly be regarded as a primitive Crustacean; and since we meet with 
abundant examples of centrolecithal segmentation both above and below Lucifer, we can not regard 
the Lucifer egg as ancestral or as the unmodified descendant of an ancestral type of egg. "We 
must, therefore, believe that the egg of Lucifer has been simplified by the loss of the greater part 
of its food yolk." 

It is to be regretted that Professor Brooks did not find material sufficiently abundant to war- 
rant the sacrifice of some of the segmenting eggs for sections; for until this is done we can not be 
certain of the origin and relations of the mesoblast and entoblast in this extremely interesting 
species. A careful study of the subject both in Lucifer and Sergestes would form a very valuable 
and much needed contribution.* 

It seems to me quite probable that we have in Lucifer a repetition of what occurs in Homarus 
and Alpheus, and that the yolk-bearing cell corresponds to the inwauderitig or delaminated cells, 
which occur in the lobster at the close of segmentation. In each case they arise by transverse 
dinsion from the superficial cells of the blastophere. In each case, also, they appear just before 
invagination, and migrate into the segmentation cavity. The differences are that in the lobster, 
for instance, the segmentation cavity is already filled with yolk ; the centripetal cells are numerous, 
and they do not necessarily come from that point on the surface which corresponds to the point 
of invagination or ingrowth. As to the comparative history of the two cells in the two cases little 

* Since tbis was writteii Professor Brooks has anuouiicecl in his report of the work of the marine laboratory of 
the Johns Hopkins University, that he has recently obtained the eggaot Lucifer in abundance at Jamaica, and is now 
engaged in studying its embryology. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



423 



can be said. Brooks tliought that in Lucifer they represented the food yolk, although this was 
not settled. In Alplieus these cells are later joined bygrer.t nnnihers of wandering cells at the 
invagination period, and out of this common stock, so far as we can detormiiie, both raesoblastic 
and eutoblastic organs are developed. In Horaarus, on the other hand, the invaginate cells 
unquestionably degenerate. 

The eggs of Scullarus and PaUmtruit have not been thoroughly studied, so far as I am aware. 
Dorhn (14), however, has figured the eggs of Scyllarus arctus in late stages of yolk segmentation, 
and in surface view they resemble, at this time, the ordinary Decapod type. We have as yet no 
knowledge of the .segmentation of the Storaatopods. 

The relations of the diflerent varieties of segmentation which are met with among the Deca- 
pods, may be expressed by the following table : 



(I). Lucifer typus. 



Segmentation of the . 
Decapod egg. 



I. Total: regnlar: seg- 
mentatiou cavity pres- 
eDt. 



II. Partial : centroleci- 
thal(yoIk pyramids): 
Begmentaticiii cavity 
filled with yulk. 



Segmentation of yolk at first to- 
tal, afterwards partial. 



^(3 



(•Regular. < 



(II). Segmentation of 
yolk. { 



Irregular 



(1) ralcmion. 

) Eupagnrus priilcauii. 
(3) Atyephi/ra compressa. 

(1) Penaus. 

(2) Crangon. 

(3) Stetiopun hispidiis. 

(4) AlpliciiK naulcyi. 

(5) Ponlotiin domcsiica. 
(fi) Hippa talpoidex. 

(7) ral(vmo»(lrn I'ulgaris. 
, (8) Ciillianaesa mcditerranea. 

(1) HomaruK americanux (yolk 

segmentation at first ir- 
regular, but later regular 
or nearly so). 

(2) Alphens minor. 



Of the Thoracostraca, the Schizopods undoubtedly depart widest from the common decapodal 
type of segmentation. Nusbaum (45) thus describes the process in Mysis Chamrlco : The pro- 
toplasm — that is, the segmentation nucleus, with its protoplasmic body — retreats to a point at the 
surface of the egg. The nucleus then suflers division, and the protoplasm becomes diiferentiated 
into an outer striated zone containing a single nucleus, and an inner granular zone with one or more 
nuclei. The single e.xternal necleus divides and gives rise to a small blastodermic di.sk, formed of 
a single layer of hexagonal cells. From the internal nuclei and protopla.sm a small number of nuclei 
are produced under the blastodermic disk. The free cells below the disk are the products (1) of 
the nuclei and formative protoplasm of the deeper layer, and (2) of the cells of the upper layer or 
blastodermic disk. While a solid accumulation of cells is thus being formed below the disk, the 
superficial cells gradually extend on all sides and inclose the egg. The thickened disk marks the 
ventral side of the embryo. It divides into a median, caudal, or abdominal plate, and two lateral 
plates, the rentral hands. Volk cells which were not present up to this stage, now arise by migra- 
tion from the abdominal plate. 

Tlie segmentation of the Schizopod is especially interesting, since it agrees so closely with that 
described in certain Isopods and Myriapods, and resembles also the segmentation of Arachnids. 

Bobretyky's observations on Oniscus {'>) need to be repeated, and especially in the early 
stages. Acconling to this observer the earliest phase of segmentation was characterized by the 
anomalous withdrawal of the egg protoplasm to the surface, where it accumulated in a distinct 
body, and underwent segmentation. A di-sk of large columnar cells was thus formed, marking the 
ventral surface of the embryo. The cells spread with the thickening of the disk, until they inclose 
the entire egg. The superficial cells form ectoblast, the rest entoblast and mesoblast. 

Morgan (41) has de8cril>ed a form of .segmentation in Pycnogonida which resembles that of the 
Decapod. Here the invagination (which leads to Uie formation of the stomoda'um) is preceded by 
the delamination of endoderm cells from the blastospbere, very much as in Alpheus, if we may 
regard the yolk cells a.s prioMtive endoderm. 



424 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

In Agekena, Locy (37) found the unsegmented egg to contain a central nucleus and protoplasm, 
united by a fine network to a peripheral protoplasmic layer, the blastema. The nucleus divides, 
and its products pass gradually into the blastema, which is used up in forming the blastoderm. 

Bruce (10) speaking first of Bobretyky's work, thus describes the formation of the blastoderm 
in Lepidoptera: 

In the earliest stages he found four aracebiform cells in the yolk, situated in pairs at opposite ends of the egg. 
Later the blastoderm isfornx^d byaranltiplication of these cells; according to Bobretyky it is not formed simultaneously 
over the entire surface of the egg. Iiut is laid down first at one or more points on the surface. This type of 8egment.a- 
tion can not strictly be called entolecithal, inasmuch as the cells are not, in the earliest stages of segment.ation, at 
the surface inclosing the yolk. All the primitive nnditferenti.ated cells do not, according to Bobretyky, reach the 
surface to form the blastoderm, but some remain ce.ntr,ally located as yolk cells after the formation of the blastoderm. 
The earliest stages of segmentation observed iu Thyridopteryx showed several amoebiform cells in the yolk in each 
cross section . 

In Thyridopteryx the blastoderm is first formed in a given area on the surface, afterward com- 
pletely inclosing the egg, but in this particular closely related insects seem to differ. 

Heider's recent observations on HydropMlus (24) show that numerous nuclei which originate 
from segmentation, do not reach the surface to enter into the " Keimhautblastem," but remain in 
the yolk as yolk cells. 

The segmenting egg of Julus terrestris is described by Heathcote (19) as a syncytium. Seg- 
mentation is at first central, and the resulting nuclei are united by strands of protoplasm. Upon 
reaching the surface they spread themselves over it to form a blastoderm. The blastodermic cells 
are united to each other by strings of protoplasm, and to the cells of the yolk. The entire egg is 
thus iiervaded by a network of protoplasm. The yolk cells are regarded as entoblast, and give 
rise to the "keel" or thickened blastodermic plate. This stage, characterized by a thickened 
blastodermic disk, keel, or cumulus, probably corresponds to a similar stage which is met with in 
Schizopods, Isopods, Myriapods, to the primitive cumulus in Arachnids and the ventral plate 
which suffers invagination in some insects. Possibly it corresponds also to the invagination plus 
the thickened ventral plate of Alpheus and Homarus. 

Possibly we have in Astacus and Homarus an approach to the mesoblastic type of segmenta 
tion, such as is found in Mysis. This would be reached in Astacus if the protoplasm (which accord 
ing Skimkewitch passes at once to the surface) should in the course of division build up a disk, 
instead of diffusing itself over the egg. A similar result would be achieved in Homarus if the 
belated cells should not reach the surface at all, and if those which are first to appear should not 
diffuse over the egg, but segment to form a thickened plate. 

Balfour says, in speaking of forms like Peniijus: 

It is probable that not all the nuclei which result from the division of the first segmentation nucleus become con- 
cerned in the formation of the snperficial blastoderm, but that some remain In the interior of the ovum to become the 
nuclei of the yolk spheres. — (Comp. Embryology, Vol. I, p. 113.) 

This, I think, is an error, and that what is true of a number of forms, as Alpheus, Crangon, 
Homarus, probably expresses the rule for the Decapods, that all the egg protoplasm enters into 
the peripheral cell layer. Exceptions to the rule may, however, occur. 

The use of the term centrolecithal to express the relations of the protoplasm and the yolk in 
the egg of Arthropods is not beyond criticism, but the strict application of a single term is clearly 
impossible. The ground of any objection is sufficiently covered by Balfour, in emphasizing the 
fact that it is the centrolecithal condition which is eventually attained. He says : 

As might be anticipated on the .analogy of the types already described, the concentration of the food yolk at the 
centre of the ovum does not always take place before segmentation, but is sometimes deferred till even the later stages 
of this ]>roces8. — (Comp. Embryology, Vol. I, p. 110.) 

In most cases the protoplasmic segmentation is at first central, or, as Kingsley points out, 
ectolecithal, and then, after passing through the intermediate stage, it is finally centrolecithal. 

The question as to whether the products of the segmentation nucleus before the yolk is 
involved, are to be regarded as independent celU was raised by Balfour, who, in reference to 
Bobretyky's work on the embryology of insects, says : 

He regards the nuclei surrounded by protoplasm, which are produced by the primitive segmentation nucleus, .as 
BO many distinct cells. These cells are supposed to move about freely in the yolk, which acts as a kind of intercel- 



JfEMOIKS OF TUE NATIONAL ACADEMY OF SCIENCES. 425 

Iiilar medium. This view does uot commend itnelf to me. It is opposed to my own observations on similar iinilci 
in the Spiders. It does not fit in with onr knowledjje of the nature of the ovum, and can not bo reconciled with tlio 
8e};mentation of hucIi types ax Spiders, or even Gupaj^urua, with which tlio segmentation in insects is uudoubt«dly 
closely related. — {Comp. Embryology, Vol.i.p. ll'.l. ) 

This discussion seems to have arisen from a confusion of tlie morj)liolo^ical and pliysiolo};ical 
significance of tlie cell. The segmentation of the nucleus and it8SuiT<)uii(liiigi)rotoi)lasm is |)lainl,v 
the only important phenomenon, and the segmentatior of the yolk is not merely a secondary process, 
but in many cases a wholly unnecessary one, as we see in the early phases of many Decapods. 
In these cases the individuality of the yolk i)yramid is temporarily sacrificed or suhordiiiatcd to 
that of the true cell, which is surrounded by unsegmented yolk. Later, when the yolk has lu'comc 
divided, the yolk segment or pyramid is gradually reduced until we get the superficial, embryonic 
cell, with more or less definite boundaries. All the elements of the egg, whether suiierhciid or 
aino'boid, are clearlj- to be regarded as cells in a fundamental, physiological sense, as shown by 
the part which they play in the development of the embryo. 

SECONDARY SEGMENTATION OF THE YOLK. 

There are traces of a secondary segmentation of the yolk in Alpheus during the second, third, 
and fourth stages; that is, from the period of invagination to the outlining of the primary append- 
ages. The yolk spheres arrange themselves in spherical clusters or balls, so characteristit; of the 
early development of nearly all the Arthropods. The yolk ball contains at least one yolk nucleus 
with ]>erinuclear protoplasm and corresponds to a yolk pyramid, being a cell in the same sense as 
the latter. Various jjhascs of this secondary segmentation may be seen by glancing over Pis. xxx- 
XXXV In one egg, which I sectioned just prior to invagination (Fig. 46), there appears a segmen- 
tation of the yolk around the central nuclei. 

Kobret/ky attributes a morphological value to the secondary segmentation of the yolk in 
Arthroi)ods, supposing it to be connected with the spreading and final establishment of the ento- 
blast. The secondary yolk pyramids or giant endoderm cells, which form the lining of the midgut 
of the embryo crayfish, he compared with the Dotterhallen of Oniscns and I'alaMiion. In PalaMnon 
the food yolk breaks up into round or polygonal pieces soon after the blastoderm is formeil, while 
in Oniscns certain cells pass into the yolk from the keel or germinal eminence and gorge them- 
selves with the yolk substance until they form large balls, which re|)resent the endoderm (Darm- 
driisenzellen). It is stated, however, by Nusbaum (4'1) that a part of the endoderm of Oniscns 
which gives rise to the gastric gland arises from i)rimitive inesoblast, and in insects the endoderm 
is formed independently of the yolk cells. The history of the yolk cells and of the wandering cells 
will be discussed in another section. 

VI — CELL DEGENERATION. 

The rapid and often extensive breaking up and final disappearance of embryonic cells in the 
course of Arthropod development is a very remarkable phenomenon, and strange to say, it has 
almost escaped attention up to the present time among the Decapod Crustacea. A study of this 
subject in Alpheus, Astacus, and Ilomarus has convinced me that the i)eculiar bodies described 
as secondary mesoderm cells in the crayfish (.")4) correspond to the degenerating, sporelike par- 
ticles which characterize similar stages in the development of both Alpheus and Ilomarus. 

In some early notes on the development of Alpheus I called these nuclear fragments "sjjores" 
(22), but the term is inappropriate if we are dealing with cells in the process of dissolution, as is 
undoubtedly the case. The anomalous "secondary cells," which have been a sort of outstan<1ing 
puzzle toembryologists, receive, in my opinion, a more reasonable explanation on the ground that 
they represent degenerating elements. This view is supported by a comparative study of embry- 
onic growth in other Arthropods. 

Alpheus. — Degenerating cells are present in Alpheus saulcyi in considerable nund)ers wlicn the 
nauplius apjieiidages are budding and increa.se for a short time beyon<l this iteriod. They continue 
in greater or less cpiantity until six to eight pairs of postoral apjx'ndages are formed, when they 
disappear from the embryo almost (completely. They vary in size from small refringent particles 
to spherical nnvsses as large as ordinary nuclei, or even larger. Many nuclei, instead of having 
the normal appearance, in which the chromatin has the form of a coil or a reticulum with stellate 



426 MEMOIRS OP THE NATIONAL ACADEMY OF SCIENCES. 

nodules in its meshes, begin to show retrogressive tendencies. They sometimes appear swollen out 
to an unusual size, and their chromatin is aggregated into a single large ball, which may become 
vesicular and strongly refractive. The cliromatin ball is sometiraes of large size, central in posi- 
tion, and stain6<l intensely, suggesting strongly the nucleus of a blood cell, or it may stain so 
faintly as to be hardly recognizable. Again, it may be eccentric and attended by one or more 
smaller balls, or the nuclear body may be filled with numerous coarse grains. These bodies then 
recall yeast cells in process of producing ascospores. As in the yeast cell, the wall of the 
nuclear body seems in many cases to break down and thus set free into the yolk the naked, spore- 
like masses of degenerating chromatin. 

In Figs. 21 and 32 (Pis. xxvii,xxix), taken from the egg-nauplius embryo, we see various stages 
of this process. Around the stomodajuni, and within or near the pockets of the antenuie and mandi- 
bles, there are large numbers of these pseudo-spores. Some are small chromatin balls (s), which 
combine actively with hcemotoxylon, while others stain feebly or are quite unaffected by the dye, 
and resemble straw-colored particles of vesiculated and altered food yolk. Below and to either 
side of the stomod;eum there is a granular residue (Fig. 118, A. Y. S.), composed of yolk and nuclear 
matter in various stages of chemical degeneration. 

The ordinary nucleus in the resting condition is generally characterized by the presence of 
balls, nodules, or granules of various sizes, which represent chromatin constituents of the nucleus. 
Under high powers these usually appear as stellate masses suspended in the nuclear reticulum. 
A number of representative nuclei are shown in Fig. IS. They are all drawn to scale and are 
taken from the egg nauplius series under review. It is so plain that it is hardly necessarj- to state 
it, that the nuclear fragments in these bodies, e,/, or h for instance, correspond to similar fragments 
which occur free in the yolk. The larger nodule in the nucleus / resembles figure b, except that 
the latter is surrounded by an outer light zone. This zone is often very large and not as sharply 
defined as in the drawing. Again, figure c resembles figure h, except that the outer light zone is 
larger in c and the chromatin or stainable residue has nearly disappeared. I regard the bodies b 
and c as masses of degenerating chromatin which have escaped from a disrupted nucleus or cell. 
In c the retrogressive changes are furthest advanced. Finally, when the chromatin or stainalile 
matter has been completely disorganized, there is left a vesiculated mass which stains very feebly 
or not at all, and resembles yolk (Figs. 102, 107, A. Y. S.). Nearly every drawing of the egg- 
nauplius stage shows one or more bodies resembling b in Fig. 18 (see Fig. 21,s, s^, and Fig. 32, s'). 
In many cases the outer light zone is cloudy, as already stated, and the element resembles a spherule 
of yolk with a ball of chromatin imprisoned in it. These bodies bear a certain resemblance to 
blood cells, but this resemblance is probably transitory, and after a careful studj' of a great many 
stages I can find no direct evidence that they are ever reorganized into new tissue. The blood 
cell of the adult is shown in Fig. 19 and that of an embryo in Fig. 35. In each case it consists of 
a deeply staining granular nucleus and a clear cell body. The nucleus corresponds to the 
apparently naked yolk nucleus (Fig. 35, Mes.; Fig. 18, etc.) and the cell body to the perinuclear 
jyrotoplasm, which is present, though often of small quantity, in the wandering cells. As we have 
already shown, it is probable that the blood cell (Fig. 35, B. C.) is derived directly from the wan- 
dering cell (Mes.), and that the characteristic appearance of the cell protoplasm is a rapid acquisi- 
tion. 

Degenerating nuclei may be seen by glancing over the plates (Pis. xxxvri-xxxixand xli-xliv), 
but it is unnecessary to refer to these in detail. 

The dorsal plate or dorsal organ (?) furnishes a most striking instance of the degeneration of 
cells (PI. XXIX, Fig. 36; PI. xlvi. Fig. 153). Its cells seem to originate from the ectoblast, with 
a<!cessions possibly from the wandering cells. After the slight ingrowth, which takes place in the 
middle of the plate, many of the cells pass into the depths of the egg and break up into meteoric 
clouds of small deeply staining particles. 

To sum up the previous remarks which relate to the appearance of these bodies in Alpheus, 
degenerating cells are first seen in Stage iv, and in the following egg-nauplius stage they are 
abnndaTit. In Stage Vli (PI. XLIV, Fig. 131) they are still present, and in Stage viil there is a 
fresh irruption of degenerating products into the yolk, arising from the centripetal cells of the 
ilorsal plate. At a slightly later period they have almost wholly disappeared. Even as late as 
in the tenth stage a few chromatin granules can be seen iu the region of the dorsal plate. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 427 

CELL DEGENERATION AND AMITOSI8 IN ALPHEUS MINOK. 

Ill the segiuentation of Alpheus minor there are numerous cases which illuHtrate the fragmen- 
tatiou iiuil apparent degeneration of nnck'i. A nuclear body sometimes seems to be breaking down 
and discharging a large number of sporelike balls or grains of chromatin (Fijr. 2(i, PI. XXVIII, S. C). 
This probably represents an clement in i»roco.ss of dissolution, if this be true, the clear area is 
similar to the plasmalike mass shown in Fig. 13, in which the nuclear bodies have disappeared from 
view. Clear areas are sometimes seen containing only minute particles of nearly dissolved chro- 
matin. The large swollen bodies, like those shown in Fig. 23, each with a single, often minute, 
ball of chromatin, certainly remind us of somewhat analogous structures which can be seen at a 
later stage in the crayfish. 

The egg sectioned iu Fig. 12, PI. xxvi, contains eight large nuclear nests or shells. The 
nuclear masses are seen to be very irregular in size, and in some instances the nuclei are unques- 
tionably breaking down. Iu other cases the egg contains a smaller number of large, very irregular 
masses of nuclear material, consisting of a fine network, with chromatin granules in suspension. 
These nuclear masses sometimes appear to be constricting into two parts. The swarm of small 
nuclei, like that shown in Fig. 13, 1 interpret, as already stated, as arising by a kind of budding of 
the large nuclear mass and the subsequent constricting ofl" of the buds. 

It is very interesting to find that in this case, possibly the only case of amitotic cell division 
in the segmentation of the ovum yet recorded, the indirect division of the nuclei is followed to 
some extent by a degeneration of these bodies. This lends some weight to the view that indirect 
division is connected with the senescence of nuclei.* 

The nuclei of the large endoderm cells lining the mesenteron in the crayfish appear to divide 
directly, and in this case the process is again followed by dissolution. In may, however, prove 
that we have here a case of multiple karyokinesis, similar to that which I have recently observed 
iu the superficial cells of the lobster embryo, where nests containing from four to sixteen closely 
packed nuclei are very characteristic of certain early stages. 

CELL DEGENERATION IN A8TACU8 AND HOMARUS. 

Homaru/i americanu.1. — I find certain bodies' in the lobster essentially similar to those which 
characterize the Alpheus embryo. If a longitudinal section of the egg uauplius of Uomarus bo 
compared with Fig. 125, which represents a similar section of a similar stage of Alpheus sauleyi, we 
find not a few chromatin balls, but a meteoric swarm of granulated bodies and naked chromatin 
grains coextensive with the embryo, and reaching a considerable distance into the yolk amid the 
scattered mesodermic cells, but perhaps most abundant, as in Alpheus, in the neighborhood of the 
stomodaHim. A long nebulous train of yolk spherules and granules extends forward a consider 
able distance in front of the mouth, and is especially marked in front of the optic disks. The 
labrum and the folds of the appendages which contain yolk abound in these peculiar granulated 
bodies. In less number they occur in connection with the endoderm cells, which have at this 
stage extended through a greater portion of the egg and form a series of irregular sacs tilled with 
yolk. Tlie.se yolk masses, with their surroundiBg sheet or advancing column of cells, correspond 
to the endoderm sac of the crayfish. In the latter the jieculiar cell bodies also occur. 

If one now examines very thin" sections under high powers, we find that the granules and the 
granulated bodies correspond in general to the structures we have found in Alpheus. The chroma- 
tin grains appear sometimes as naked masses in the yolk ; sometimes they possess a distinct proto- 
plasmic body. The degenerating chromatin stains either very intensely or faintly and is often 
vesiculated; that is, it appears as a hollow shell. Under favorable conditions it is easy to demon- 
strate the fact that thc^se bodies surround particles of yolk, and occasionally they have a crescentic 
shaiie, when it can be clearly seen that they are enwrapjiing a yolk spherule. This vitelloi)hilus 



* While this memoir was in press a paper was received on Amilosit in the Embryonal KnreJopes of the Scorpion, by 
H. P. JohiiHim, (Riillotiii of the MuNenm of Coiiipsiral.ivo Zoology, Vol. xxii, No. H). Only two inHtanooR of iliroct cell 
division in tlio onibryo of Arthropods aro rcoonlcd : that fonml l>y Cnrnoy in tho vontral phito of /I i/drnph il im piceiin 
and tbo caso \vhi<'li Wliocler has di^scribod for tho blaHtodprin of HIatIa germnnica. Mr. .Johnson linds that do-'cn- 
eratiou does not always follow upon inilirect cell division, as iu the case of aiuitosis in the testicnlar cells of certain 
Isopods. 



428 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

cbaracteristic is certainly not so apparent in Alpheus, yet I believe that in tbis form it is present 
in some stages, though in a less marked degree. 

A staeiis (?) — I have studied several critical stages in the development of the craytish, critical at 
least so far as the appearance of degenerative products is concerned, with an eye to comparison 
with Alpheus and Hoinarus* The youngest set of embryos corresponds nearly to Eeichenbach's 
stage E, but differs from it iu some details. Rudiments of five pairs of appendages are present, 
the two maxilhB being seen between the mandibles and the thoracic-abdominal process. None 
of the appendages, however, are folded. The mouth is seen on a line between the first and second 
pair of an ten n;*. 

The bodies which Reichenbach calls "secondary mesoderm" occur in abundance in or near the 
wall of the endodcrm sac next the embryo. They also abound in the yolk under the ectoderm, 
and ai'e most numerous in the area extending from the optic invaginations to the mouth or slightly 
behind it. In thi§ respect they recall the distribution of similar bodies in Alpheus and Homarus. 

I wish to call attention to the fact that at this stage none of my sections show a cavity in the 
endoderm sac, as is represented by Reichenbach (compare Taf. viii, 54), and the endodermal yolk 
segments or pyramids do not always possess completed walls. To what extent this appearance is 
normal, and to what extent due to the action of reagents, I can not at present say. These eggs were 
treated with hot water and corrosive sublimate. The endodermal nucleus is surrounded by a thin 
layer of protoplasm, which works its way amid the yolk so as to practically surround a pyramidal 
mass. This strongly recalls the serpentine manner in which the endoderm cells creep through the 
yolk in Homarus. Whether these cells iu Astacus are simply migrating in a column or sheet, 
spreading gradually towards the periphery of the egg, as in the lobster, cannot be decided from the 
material at my command, but it is a point of considerable interest in its morphological bearings. 
The endodermal cells probably multiply indirectly, but I saw no nuclear figures in my sections, 
and they appear also to divide directly, independently of the yolk pyramids as Reichenbach 
has described, giving rise to the chromatin balls and granulated elements (compare Fig. 20) but, 
as pointed out above, this appearance may be very deceitful. This process is most marked in the 
endodermic area noticed above, underlying the anterior half of the embryo. Here we see great 
numbers of the bodies of varying size, both within and without the domain of the endoderm cells. 
They closely resemble the vitellophagous elements which I have described for the lobster, and 
possibly they attack the yolk in a similar way. Where they are thickest the yolk is comminuted 
and shows traces of profound chemical change. In the midst of the altered yolk one can discover 
very faint outlines of vesicular bodies which exhibit but slight reaction to the stain. These I 
regard as degenerated cells. • 

The next stage of Astacus which I have studied corresponds nearly to Reichenbach's stage G. 
Eight pairs of appendages are present, and there are rudiments of a ninth pair. The first and 
second maxillre appear as distinct buds, while the third pair of maxillipeds is represented by a 
proliferating cell area ouly. The extremity of the abdomen is not bifid. 

In the central part of the endodermal sac there is a coagulable fluid which comes in close rela- 
tion with the posterior end of the embryo. The ^udodermal cells laterally have quite or nearly 
reached the ectoderm, while dorsally they fall a little short of the surface. The yolk within the 
confines of the endoderm has an irregular, pyramidal, or rail^al cleavage. Centrally the yolk 
blends with the serum-like fluid, in which occasional granules or balls of chromatin may be found. 
Small spherical elements (like those represented in Fig. IS, a, h, c, or 7i, 7i,' Fig. 20), containing a 
single chromatin ball or several balls, occur not only in the yolk underneath the ectoderm and iu 
the vicinity of the endodermal nuclei, Mit also in the central yolk of the endoderm sae, at various 
levels below the endodermal nuclei. This is a point of some interest in connection with the fate 
of these bodies. They wander not only peripherally but centrally. Rarely we meet one which is 
three or four times the average size, having a small chromatin spherule in its center. In later 
stages they are present in far less numbers. 

* For the opportunity of studyiug tho crayfish ilevolopmeiit at this time I am indebted to the kiadness of my 
friend, Dr. William Patten, who sent me a, number of important Hiages collected at Milwaukee. 



MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 429 

Reicbeubach thus suinmames his observations on the "sekuudsire Mesodermzellen :" 

Die fragliubou Elemeuto siuU aU ZoUeu zu duuteu, dureu Kerne uicht imiiiur die Bescliaffeuheit gewuhulicber 
Zi-Ilkeriio li;»l)nii, diesulbu aber friibi-r odor sp.'iter orhuigeii ^Fig. tiO, in, in', Plate xxvil). .Sie uehiuen ibron IlrMiirung 
iuiierbalb lUijiMiigeii Eutoderui/.illen, wclcbo dio ventralo Waud des Urd:iriM»;ickcbt!!i» ziiBaniniensctzon dtircb oiiio 
nilber zu urt'oiuclicndo Art eudogeiier Zcllbiiluug, bei welcbtT dio in der Melirzulil in den Elenienten des Eiitodeniis 
vorbaudciicii Ivirno eine wicbtigo Kollo zn spielen scbeiuen. In den deui Stadium I) vorangebeudon Eiitwicliluug- 
sporiodoii liat Jode Eiitodermzelle ujoist uur eineii Kern ; dies tritU aucb uocb zuiu Tbi^l fiir Stadium D zu. Bald ver- 
uiebreu sicb abor die Eutodermkerue ganz orbeblich und eudlicb begiiineu dio sokuudiiiou MosodermzoUen aufzutreten. 
Wcnu oiuo griissero Zabl dor sekuudiireu Mcsodorujzelleu in deu Entodermelomenteu liegeu, so scboiut das Kerunia- 
torial verbrauobt zu sein. Es wauderu uuu aller Wabrscbeiulicbkeit uacb dieso Zollcn, deren Korno auscbeiovud 
uock in dor Metamorpbose sicb botiuden, aus dom Entoderm aus uud bcgeben sicb unter die Embryouabmlage. Die 
V.etroft'oiidou Contouren des Eutodornia lasson oft nocb Spurou dioser Wanderung orkennen. Ob sie wirklicli aktiv 
auHwainlern odor aucb ausgestosseu nerdeu, ist nicbt festzustelleu gewoson. Sie begebeu sicb nun untcr dio librigeu 
Mosoderuizollen und siud bald uicbt mebr vou ibuen zu untorscbeiden. Aus diesem Gruud fiibrto icb liir sie deu 
Nanien "sekundiiro Mosodormzellen " eiu, wiibrend die altereu Urmosoderuizellen als priuiiire bezoicbnet werden. 
Da die letztoreu dio Tendenz zeigon, zu kompaktereu Massen zu verwachseu, so darf man wobl vermuteu, dass die 
sekuudiireu Mesodermzellen die Blutzelleu liefern werden (54, p. 36). 

It is interestiug to uotice that in Alpbeus, Astacus, and Homarus degenerating cells appear 
in greatest force at about the egg-naiiplitis stage, and from that time on their numbers begin to 
wane. In Astacus, Eeicheubach first noticed the " sekuudiire Mesodermzellen" in stage D (that 
is, when the optic disks, the thoracic-abdominal plate, and the mandibles are outlined), which nearly 
corresponds to Stage W of Alplieus. In stage D the bodies in question are most abundant under 
the optic disks (Koptlappen) and in the region of the upper lip, but become more generally dis- 
tributed in the egg-nauplius. 

According to Keichenbach, " gastrulatiou" takes place after the optic disks are formed, but 
unfortunately his paper is incomplete at a very important period, namely, from the late yolk-pyra- 
mid stage of segmentation, when the protoplasm is at the surface, to the time when an embryonic 
disk or plate (Entodermhiigel or Entodermscheibe) has been formed. It is impossible, therefore, 
to follow the history of the so-called " white yolk elements." Ue says of the latter : 

Sie besteben aus protoplasmatiscber, feinkornigor Substauz uud enthalten vacuolenartige Eiuscbliisse, die ibuou 
eiu scbanmiges Ausseben gobon ; icb babe sie als woisse Dotterolcmente bezoicbnet. Sie liegen ontwoder dicbt unter 
dom Blasto<lorni D<ler im Centrum des kugligou Eies und verscbwinden -sobr bald (Op. cit., p. 7). 

According to my view these bodies correspond to the vesiculated elements {in, Fig. 20), and 
both represent cells in process of dissolution. If Figs. 18 and 20 are compared (the latter being 
a copy of lleichenbach's Fig. 67) we will find a striking correspoudence between these peculiar cell 
products in both Astacus and Alpbeus, a correspoudence which is even more marked wheu the 
comparison is made with the lobster. 

Keichenbach emphasizes the statement that naked balls of nuclear material never occur free 
in the yolk outside the endodermal sac. In this yolk they always have a "cell body" as K, Fig. 
20. It is an easy matter, however, to distinguish naked masses of chromatin, minute spherules, 
or smaller granules in the yolk of both the lobster and Alplieus. 

Jly studies of the lobster are not yet completed, but from the observations which have already 
been made I draw the following conclusions: In Alpheus, the lobster, and the crayfish Similar 
bodies make their api)earance at nearly similar times and play a similar role. Tiiey are derived 
from all three layers of the germ, and in AlpheuH minor degenerative products make their appear- 
ance in the .segmentation stages. They tend to break up and ingest the yolk and to produce in it 
a chemical change, possibly in order that it may be more easily assimilated by the other embry- 
onic cells. Having performed this task they degenerate ; they are converted into a substance 
resembling yolk aud function as nutrition. That any play a formative role, giving rise to blood 
cells for instance, as lleichenbach supposes, there is no direct evidence. The vitellophagous func- 
tion seems to be in abeyance in Al[>heus, but in all cases the yolk is comminuted and chemically 
ciianged in the neighborhood of these bodies. Nusbaum (45), following Morin, believes tliat the 
'•white yolk elements" arise from the segmentation nucleus and migrate to the surface of the egg; 
that they give rise to the "secondary mesoderm." which are taken up along with the yolk by the 
anueboid, endodermal cells. This is reversing the account, and, in so far as the origin of the ".sec- 
ondary mesoderm" is concerned, it is not supported, so far as I am aware, by a sia^tle obsi*jvation. 



430 MEMOIRS OF THE NATIONAL ACADEMY CF SCIENCES. 

Ishikiiwa (27) fluds iu Atyephyra after the close of the iuvagiuatiou stage, certain proto- 
plasmic eleiueuts uuder the ectoblast, which he thinks may correspoud with the " white yolk cle- 
lueuts" just referred to, aud he also ideutifles-" secondary mesoderm cells," but does not trace 
their origin or function. ' They are " small granules," easily stained by logwood solutiou, and some 
are of considerable size and have a clear cell outline. "These are mostly aggregated in the 
cephalic regiou between the involutions of the ectoderm cells, but are also found in all places." In 
time of appearance aud in their position, he says they seem to correspond to the " secondary meso- 
dei-m cells" of Astacus. This short uotice with his figures leaves little doubt that these bodies are 
similar to those just described iu Alpheus and Homarus. Fig. 62 of his paper represents a longitu- 
dinal median section of the egg nauplius, and may be compared with the same stage of Alpheus 
(Figs. 104, 105), with respect to the general character and appearance of the degenerating cells. 

I have noticed similar nuclear fragments in the egg-nauplius of a crab (Fig. 113, PI. xl), aud 
Lebedinski (34) has described "secondary mesoderm" in the embryo of the Mediterranean sea 
crab, Eriphia spinifrons. According to this observer they are found in all stages from the " gastrula" 
on, to the egg-nauplius; they are derived from ectoderm, and i«-obably give rise to blood cells. 
In the stage with one pair of maxillipeds these elements are in active proliferation : 

Mau findet, die Zellen desselben bieten verschiedene Momente uud Zastande des Zerfalleas <lar; dieses Zerfallen 
der Zellon stoht iu geuauen Zusammenhiinge mit der Entstehung der Blutliorper. 

He further says : 
Ueber die Bildung des Blutes kann ich nlchts bestimintee mittheilen. Im Stadium des ersteu Paars kieferfussoheu 
siud die ersten Blutkiirperclien vorhaudun, welche zuni ersteu Mai im Beroiche des Herzens vorkommen, wo sich auch 
am friiliesten das sekuudiiro Mesoderm riickzubilden beginnt. 

From these quotations it appears that the " secondary mesoderm " shows signs of degenera- 
tion, and its conversion into blood cells is an unverified inference. It seems more probable that 
the structures iu question correspond with similar bodies already noticed iu Alpheus, Homarus, 
and other Decapods, aud that in all cases they have to do primarily with the dissolution aud uot 
with the construction of cells. 

Wheeler (07) iu his careful paper on the development of the Cockroach and Potato beetle 
(Blatta germanica and Doryphora decemlineata) describes an interesting case of the decomposition 
of nuclei, which bears a close analogy to what takes place in Alpheus and probaldy also in 
Astacus. In Doryphora two masses of endoderm are found, one uuder the stomod;eum the other 
under the caudal plate. At both these places numerous cells which originate in the endoderm 
pass into the adjacent yolk and disappear. The process of dissolution is described as follows : 

Tile karyochylema becomes vacuolated, probably with substances absorbed from without, to judge of the larger 
size of some of these nuclei, while the chromatin ceases to present the threadlike coil .aud becomes compacted into 
irregular masses between the vacuoles. Finally the vacuoles fuse and the masses of cliromatiu, formally numerous, 
agglomerate to form one or two large irregular masses which usually apply themselves to the wall of the clearly vesic- 
ular nucleus * " * In the last stages seen the masses of chromatin lie between the yolk bodies, all other portions 
of the nucleus having disappeared. They still take the deep red stain, but finally become comminuted .and disappear 
in the intervitelline protoplasm. 

The vesiculated elements recall similar bodies which appear iu Keichenbach's plates. Thus 
the element t, Fig. 88 of Wheeler's paper, where the chromatin is applied to the walls of the 
nucleus, strikingly resembles nucleus i, Fig. 20 (see this paper), where the chromatin is similarly 
disposed around the wall of a vacuole. 

Bruce (10) figures certain yolk cells undergoing what he considered to be endogenous cell 
division iu an advanced embryo of a spider, aud compared it with the endogenous cell division 
which Ileicheubach describes as taking place iu the endoderm cells of Astacus. 

The disintegration which has been attributed to the leucocytes of the mammalian blood 
affords an interestiug comparison with the phenomena which have been described for the Arthropod 
embryo. Howell's careful observations (25) support the view that the multiuucleated leucocytes 
are disintegrating cells. " The leucoblasts enter the lymph stream, and eventually reach the 
blood as unicellular leucocytes." Here they undergo changes, acquire amoeboid movements, while 
the nuclei elongate, become constricted, and finally fragmented. " The nuilti nuclear stage * * » 
is probably followed by a complete dissolution of the cell." Howell adopts the highly reasonable 



MEMOIRS OP TUE NATIONAL ACADEMY OF SCIENCES. 431 

view tbat tbu iiuclciir fragiuent^s persist for a while iu the circulatiou as the blood plates, and 
considers it probable that the latter take some part iu foriniug the paraglobuliu of the blood. If 
the blood plate is then a degenerate body, it may be compared to the s[)ore-like masses of chro- 
matin, which are discharged from the disrnpted cells iu the lobster or crayfish embryo. 

VII.— TUE OlllGIN AND UlSTORY OF WANDKUING OKLLS IN ALPHKtJS. 

The wandering cells iu 2\.lpheiis have a triple origin, from the blastosphere, from the invagina- 
tion, and fron» the thoracic-abdominal plate. Those which arise from the blastula at the close of 
segmentation are, perhaps, the representatives of a primitive endoderm. Following the invagina- 
tion, a thick pad of cells is formed, the ventral or thoracic abdominal plate. From this plate a 
general migration of cells occurs on all sides int« the yolk (Pis. xxxii-xxxv). While there is a 
great tendency to migrate to parts underlying the embryonic area, the cells nevertheless wander 
to all parts of the egg, even to those most remote from the embryo. The first of these wandering 
bodies which originate from the blastosphere have been called "primary yolk cells." The latter 
classes may be called "wandering cells." Since these classes cau not be distinguished after a 
certain period, I refer to all cells which move about in the yolk and have no direct connection with 
the thoracic-abdomiual plate, and the parts of the embryo iu front of it as wandering cells. I have 
been somewhat at a loss to find a suitable term for these bodies, since there are obvious objections 
to the use of "yolk cells'' or "yolk nucleus." Where these terms have been employed in the ju'esent 
paper, they must be understood to refer to the wandering cells which have been defined above. 
The term "embryonic nuclei" is used for couvenience merely to discriminate the remaining nuclei 
of the egg from those of the wandering cells. 

The object immediately iu view is to determine the fate of these wandering cells, to ascertain 
what formative role they play while the mesoderm, and more particularly the endoderm, are beiug 
differentiated into definite cell layers. In the following account, cells which have i)arted all con- 
uectiou with the thoracic-abdominal jtlate and have entered the yolk are enumerated as wandering 
cells. In an earlier part of this paper I gave au account of the origin and suj)posed fate of the 
wandering cells, the general conclusion beiug that iu the early stages (Stages iii-v) they pass 
froni the yolk to the embryo and to the extra-embryonic parts* of the egg, and contribute to both 
mesoblastic and entoblastic structures. 

A number of friends to whom I showed my sections objected to this interpretation on the 
ground that these wandering cells could be regarded with ecpial probability as originating, in some 
measure at least, in the o|iposite way, that is, as budding from superficial cells not concerned with 
the thoracic-abdominal plate, aud migrating into the yolk. A careful study of successive stages 
would not sui)port this idea, but the objection could not be satisfactorily auswered, aud neither 
view could be readily proved. I therefore undertook a renewed and more precise study of the 
wandering ceils in Alpheus, aud I think that their fate has been definitely settled. 

The number of wandering cells which occur iu the yolk, and the number of " embryonic cells" 
(that is, all the other cells of the egg) have beeu enumerated in five different stages, including 
seven different embryos, from the period of delamiuation at the close of primary yolk segmentation 
to the early egg nauj)liufe condition (Stages ii-v.) This covers the most important period so far as 
the wandering cells are concerned. The rate of increase of both wandering cells aud embryonic 
cells has also been determined for the successive stages, and the data are given in Table i. 

' There is a, certain convenience in thus referring to the embryo proper aud to the less difierentiateil regions, while 
it is understood that all the cells constitnto the embryo. 



432 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Table I. — Showing the number of nuclei in yolk, and the number of other " embryoniv n itdei," and the 
relative increase and decrease in these bodies from the close of yolk-segmentation to the egg-iuitipHus 
period. 



stage. 



II. Delamiuation (Figs. 38-45, 46, PI. 

XXX) , , 

TT !„.„„:, ♦;„„U«)F'g8-49-!J5,Pl.xxxi 
II. Invagination^^ j^ ^1^ ^g^^; p, ^^^ 

III. Optic disks (Pis. xxxii.xxxiii) 

IV. Fir8tauteuua;,mantlibles(Pl8. xxxiv, 

XXXV) 

(a) Fig8.34,Pl.xxix; 



Early egg-nau- 
plius 



107, PI 



101-105, 

XXXIX.. 

(J) Figs.34,Pl.xxix-,) 
]01-10.=i. 107, Pl.S 



101-105, 

XXXIX . . . 



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59 



* Primary yolk cells. 

t Number obtained by metliod Ueacribed bolow. 

The distributiou of the wauderiug cells and of the embryonic uuclef is also illustrated by a 
series of curves, constructed in the following manner : Each vertical row of the smaller squares 
corresponds to a section of the ovum (Sections Nos. 1, 2, 3, etc.), while each square iu this row 
represents a single nucleus. The number of nuclei in a section is shown by the number on the 
line where the curve makes a bend or intersects the middle of the lower side of a square hiuclei 
Nos. 1, 2, 3, etc.). Thus where the descending line of the curve in Fig. 5 stops in section No. 2, 
making an angle in the fifth vertical square, counting from the upj^er base line, this implies that 
in the second section of the egg, corresponding to this vertical area, there were five nuclei which 
did not appear in the following or preceding section. 

The number of nuclei were determined in the following way : Camera-lucida drawings were 
made of every section of a given series on thin paper and each nucleus was marked. Then, by 
superimposing upon each drawing the drawing of the section immediately following, every nucleus 
new to that section could be determined in the early stages with absolute certainty. The number 
of primary yolk cells and wandering cells were thus counted in all stages. In the older embryos 
(see numbers marked with dagger in Table i. Stage iii-v) where this method became impracti- 
cable with reference to the total number of embryonic nuclei, their number was estimated iu a 
different manner. The nuclei appearing in each section were counted aud the total number of 
nuclear sections was thus obtained for the whole series. Then the percentage which the actual 
number of nuclei in the egg bore to the total number which appear iu sections could be determined 
approximately by the method described above applied to a number of lateral sections, that is, by 
actual count of nuclei iu a favorable part of the series. The percentage which the actual number 
of wandering cells bears to the total number appearing in section could be exactly determined aud 
compared with the former estimated percentage. The percentage which involved the wandering 
cells was in the average of all stages a trifle the smaller, showing that the yolk cells wei'e, on the 
average, a little larger than the other embryonic nuclei. In Stage ii before invagination the super- 
ficial nuclei are the larger, while after invagination the diflerence is at first very slight indeed. 
In Stages III and iv the wandering cells are markedly the largest iu the egg, while in Stage V they 
either equal or fall slightly below the size of the other embryonic uuclei. 

This method presupposes a perfect series of sections of uniform thickness. These conditions 
were approximately fulfilled. The egg (i""™, or ^, inch iu diameter) was cut, on the average, into 
57 sections, each section being yir™™ in thickness. The size of the egg, neither too small nor too 
large, rendered this siiecies (called throughout this paper the Bahaman variety ot Alpheus heter- 
ochflis) most favorable for study so far as technical difficulties were involved. 



MEMOIRS OF THE NATIONAL ACADEMY CF SCIENCES. 



433 



Stage ll.—Olose of yolk negmentatioti— Formation of yolk cells, followed by invagination.— A 
siirftice view of tliis egg is given in Fig. 47, Tl. xxx. The curve (Fig. 5 of text) shows that the 
blastotlermic colls are distributed very unifonnly. In other words 
the embryonic area is not as yet marked ott". The distribution of 
the primary yolk nuclei, of which there are exactly thirty-four, is 
shown in the constructed ligure (Fig. 3), which represents the egg 
as it would appear if the yolk were transparent and the nuclei 
opaque. The distribution of these nuclei through the egg is given 
more completely by the curve (Fig. i). The only qnestious which 
need detain us in this stage are, how do the primary yolk cells 
arise and from what part of the surface do they come J Karyo- 
kinetic figures, which abound among the surface nuclei, ought to 
furnish an immediate answer to the first question. In this egg no 
less than sixteen" nuclei are met in various i>hases of division, fif- 
teen of these belonging to the superficies and one to the central vu-.. 
portion of the yolk. Clusters of two and rarely of three nuclei also "'•'*'"'• '^""'""'"'••' '"^""' "'"''' »'•««'>"». 

shuwtut; III! tlu) primary yolk **ells. For 

occur at the surfiice, sbowiug that cell division is active. In every .u-taii^, s^e Table i. sta-o n (Drian.ii.a. 

case the cleavage is radial or perpeudicular to tlie surface, and in no ****"* 

instance have I seen an unambiguous case of delamiuation (v. PL xxx), It^s possible, however, 




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For further detjuls. eonipKre Table 1, Stiigi! II (Delamination). jl^Antcrior; i"=PoH(4-rior. 


i 1 " I 




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Fig. 5. — Cnrv*; Hhowint; the (U.stribution of nuck'i at tin* Hiirfare (thai ih. niirlci of thu embryuuic cuUa. exclusive of priiuiuy yolk cells) 
of the ogE rcprc8t*nt*'<l hv Fi;;^. W aud 4. For dotaila, aco Tabh- l. Sla;;*' ii (r>i?hiiiiiiiaiion}. 

S. Mis. 94- — 28 



434 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 




that the primary yolk cells are formed iu this way rather thau by emigratiou, and that my failure 

to detect the actual process is due to the fact that I did not sec- 
tion exactly the right stage, the egg shown in Figs. 38-45 being 
a tritle too old. Iu Hoinarus the primary yolk cells arise by 
delaiuination, as I have already shown iu a preliminary paper in 
the develoi)meiit of this form (23, Fig. 5). 

Sections of this stage show conclusively that the primary 
yolk nuclei do not come from any one point on the surface, but 
that the majority of them may come from a restricted area of 
the egg. In Fig. 3 about two-thirds of the nuclei present are con- 
fined to the lower (ventral 1) surface of the egg. They are in 
various degrees of progress from the surface toward the central 
parts, which the majority have already reached. 

The formation of primary yolk cells is followed by the in 
vagination and iugrowth of certain cells at the surface. The his- 
tology of the embryo at this phase is given in PI. xxxi, and Fig. 
(5 (of text) is constructed from the entire series of sections to show 
all the primary yolk nuclei present. The plaue of the paper (sup- 
posing the drawing to represent a sphere) nearly passes through 
the point of invagination (in.). 
Iu order to test the accuracy of the method, two eggs of this stage were studied [a, ii and b, 
tl ot Table i), and the results show a remarkable agreement. Thus there are exactly thirty-seven 
primary yolk nuclei in each egg, and the total difference in the number of embryonic nuclei in the 
two eggs is only nine. Curves were constructed to show the number and distribution of yolk nuclei 
and embryonic nuclei in both eggs, and the two are introduced here because of the striking simi- 
larity. Figs. 7 and 8 are constructed from the egg seen in Fig. (ii, «, of Table i). Figs. 10 and 
9 represent corresponding curves constructed from the second egg (ii, h). The two sets of curves 
tell exactly the same story iu each case, and it is not necessary to dwell upon it. 



Fig. 6. — Diagram of egg iu invagination 
.stage, constructed from serial sections, to 
show all the primary yolk nuclei present. 
For details of this egg, see Tahle I (II, rt). 
Invagination. /7i=^point'of invagination, 
nearly iu the plane of the paper. 















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Fm. 7 — Curve constructed from serial sections, showing the distribution of the iirimary yolk nuclei iu the egg represented by Fig. 6. 
(See Table i, Invagination stage, ii, a. ) 

The bulk of the primary yolk nuclei are placed near the center. Of tlie thirty-seven nuclei in 
rt, II, twenty-two are in the ventral (?) hemisphere of the egg, and tifteeu in the dorsal. In egg 6, 
II, twenty-oue nuclei are situated in the ventral half and sixteen in the dorsal. Thus these yolk 
nuclei iucliue toward the ventral side of the egg, and hence, as already inferred, are probably 
derived in great measure from that part which corresponds to the embryouic area. 

The curves showing the relations of the embryonic nuclei (Figs. 8 and 10) read from eud to 
end of the embryo (posterior to anterior), the sections being transverse to the longitudinal axis. 
The greatest depression naturally occurs in the region of the thoracic-abdominal or ventral plate 
{Ah. P.), near the center of which is the point of invagination. In fit)nt of this there is a more 
extensive, but less depressed portion, corresponding to the embi^youic area [E. A.). The number 
of cells entering into the ventral plate at this time are shown in Table ii. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



435 



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Abp. EA. 

I'lii. Ill— I urvf sbowiug distribution of all nuclei, excluaivc of primary yolk nuclei, in the same egg as rtprescntod by Fig. 9. (See u, 
e>, Table I, and compare with Fig. 8.) ,i,AuttTior; P.rostorior; 46;;, Ventral plalc 1 £ J., Embryonic area. 



436 



MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 

Table II, 



Stage. 


Nuclei at 

surface or 

Ab P. 


Nuclei in 
Ab. P., be- 
low sur- 
lace. 


Total num- 
ber (if nuclei 
in Ab. P. 


Primary 
yolk nuclei. 


EeniainiDt; 

embryonic 

nuclei. 


Total num- 
ber of imclei 
of egg. 


a, n 

b, II 


56 

5a 


60 
48 


116 
' 100 


37 
37 


305 

330 


458 
467 



Of tbe forty-eight to sixty cells which appear hehiw in surface at this time in the ingrowing 
cell mass, a large number (twenty in b, ii) are [)artiiig coiii[tany witii their lellows and beginning to 
migrate into the yolk. So that at this stage the primary yolk cells receive their first recruits from 
the ventral plate. 

Stage III. — Optic disks and thoracic-abdominal or ventral plate. — Wamlering cells now become 
a very marked characteristic of the Alpheus egg (Pis. xxxii, xxxiii). We see by Table i that the 
total number of yolk nuclei has come up to 199, an increase of 81 per cent against an increase of 
only 4li per cent on the part of the othf^r embryonic cells. In other words, the wandering cells have 
increased nearly twice as rapidly as the other nuclei of the egg. It is, perhaps, hardly necessary 
to point out that this rapid gain is due to at least four possible causes : (1) to the multiplication of 
primary yolk cells, probably the least important; (2) to the irruption into the yolk of invagiuate 
cells, or cells derived from these, the most important source; and (3) to the multiplication of the 
latter in the yolk itself; and (4) to migration from the ventral plate, which is formed by a thick- 
ening about the point of invagination. 

The curve showing the distribution of wandering cells at this stage (which is not figured) is 
nearly bilaterally symmetrical. The greatest depression is in the region of the thoracic-abdominal 
plate, while on either side of this there is a marked drop in the curve, answering to nuclei which 
underlie the optic disks and tbe parts behind them. (Compare Fig. 11 of text.) 

A considerable number of cells have migrated to points near the surface both behind the 
ventral plate, to either side of it, and immediately in front of it (see Figs. 56, 58, 59, 60). A very 
few have wandered out to points just beneath the optic disks. Quite a number have started in the 
direction of the dorsal surface of the egg, but none have reached it. 

Stage IV. — Rudlmmts of First Antenncc and Mandibles. — Tliis is the most interesting stage 
in some respects (see Pis. xxxiv, xxxv), since it is critical so far as the fate of the wandering cells 
is concerned. 











































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Abp. OD. 

Fig. 11, — Curve showiii:; tlic distribution of Avaiuli-rinj; lells in Stneo TV. mdimi^nt.'* nf lir-^t nntcnnrn and niandibU'S present. 
PI. xxxiv. and Jor numerical dctail.s. sec Table i, .Stage iv.) Abp. region ui" v.-utral plate; O />. Kcgion of oi.Iir discs. 



{Compare 



MEMOIRS. OF THE NATIONAL ACADEMY OF SCIENCES. 437 

Table i ssliows tlie reiuaikahlf. (act that the percentage of increase of wandering cells, which 
in Stage iii was twice as great as that of other embryonic nuclei, has now dropped until it is actually 
less than the hitter. This means that the wandering ceils are mnltiidyingless rajiidly or that their 
numbers are being depleted. Tiie relative increase of yolk nuclei from Stage li to in, and from 
Stage m to iv, namely, 81 percent and 17 per cent (showing a marked falling off), is not specially 
significant, since these nunduTs depend largely upon the age of the embryo or time which elapses 
between successive stages. But this element does not enter into the relation which exists between 
the relative increase of wandering and embryonic cells in the same egg, expressed by SI per cent 
and 41 per cent, respectively, in Stage iii an<l by 17 per cent and 2(1 per cent in Stage iv. 

The curve constructed from Stage iv (Fig. 11) shows the wandering cells much more widely 
diffused through the egg than at any earlier period. The thoracic-abdominal plate is no longer 
sharply marked off from adjacent parts, and a considerable number of nuclei underlie the optic 
disks. 

In this egg there are thirty-seven nuclei in various i)liases of karyokinesis (Figs. 70, 75); two 
belong to the yolk, three to the deeper cells of the thoracic-abdominal plate, and the rest to the 
surface cells of the embryo. In the optic-disk region a very few cells appear to be delaminating; 
the rest are cases of radial division. Cell disintegration has not yet become a disturbing factor in 
the enumeration of cells. There are but two nuclei in the egg, one in the yolk, the other in the 
deeper part of the ventral plate, which show any traces of dissolution. 

The above facts lead to the conclusion that the wandering cells are being rapidly depleted 
at this time, that they leave the yolk in considerable numbers and attach themselves to tiie 
growing embryo and to the extra-embryonic surface of the egg. They thus warrant our interpre- 
tation of a cell like ye, Fig. 70, or J/f',Fig. 71,as a migrant from the yolk. While the wandering cells 
are being rapidly depleted, it does not of course follow that they never receive any recruits from 
any part of the egg without the limits of the ventral plate, and it requires no very elaborate calcu- 
lation to show that wandering cells are making early coiitributiqns to the mesoblast, but the study 
of individual sections aiul the facts brought out in Table i, prove beyond a doubt that the only 
cells which enter the yolk, up to this time, arise from one of the three sources already named, the 
blastoderm, the invagination, and the ventral plate. 

Staiie V. — Eog-Xaiipliitx. — The early egg-nauplius stage is represented by two individuals, 
one (V. a. Table i) cut in transverse and tiie other (v. h) in longitudinal vertical i>lanes. Kesi)ect- 
ing the wandering cells we now notice: (1) that their numbers have markedly decreased; (2) that 
they are far more widely and evenly distributed; and (3) that many are close upon or in contact 
with the embryo or with the general surface of the egg. 

In egg V, b (Table i) the number of yolk cells is oidy one hundred and twenty eight, consid- 
erably le.ss than are present in Stage ill, a decrease of 87 per cent, while in the other egg the 
decrease is 21 per cent. On the other han<l, the rate of increase of embryonic nuclei is greater 
than at any previous stage, .")'.) i)er cent in one egg and 6!) per cent in the other. That this is not 
explained by a large interval of time existing between Stages iv and V is shown by the fact that 
during the period (Stage iv aiuI Stage v, h, Table i) the total number of nuclei of the egg has 
scarcely more than doubled, while the iiercenlagc of increase of embryonic nuclei has more than 
trebled. Between Stages ii, a, and iii, on the other hand, the number of nuclei has nearly doubled, 
while the i)er(^entage of increase of embryonic nuclei has risen from .'?2i to oidy 42. 

How is this very rapid increase in embryonic lUK^lei and coiirdinate decrease in wandering 
cells explained in the egg-nauplius stage? The conclusion reached in Stage IV ajjplies here also, 
with a certain restriction. The problem is now not a simple one, sin(;e perturbations caused by 
the disintegration of nuclei ajipear to some extent in this stage. The diminution in ilie number of 
wandering cells is now due to two causes, to cell disintegration and to the gradual subtraction of 
cells from the yolk by cmigraticm. Disintegration of cells occurs both in the yolk and in i)arts of 
the embryo. It is i)erhai)S most marked near the line of contact of the yolk with the embryo. Yet 
the embryonic cells are meantime making a rapid net gain. 

We are thus warranted in our conclusion that the wandering cells, whiclj spread far and wide 
through the egg, play a formative role in development, to a large extent at least. This conclusion 
is rendered certain by the changes which ensue between Stages ii and iv, already noticed. The 



438 



MEMOIRS OF TEE NATION^AL ACADEMY OF SCIENCES. 



percentage of increase of wandering cells between Stages ii and iii is double that of tbe embry- 
onic cells. Between Stages iii and iv tbe increase per cent of wandering cells is less than that of 
tbe embryonic cells, and np to this time cell disintegration is rnled out as a disturbing factor. 



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Fio. 12.— Curve showing diatribution of wunderiEK cells in Stage V (Early egg.nauplius) . (Compure Fig. 11, and lor details, see Table ' 
I, Stage, II b.) E A, Embryonic area: Mo, Mouth. 

The second fact which was pointed out as characteristic of this stage, the distribution of the 
yolk nuclei commensurate with that of the yolk itself, also points to the conclusion already reached. 
This is well shown by two curves (Figs. 12, 13). In curve 13, which is constructed from a series 



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Fl(i. 13.— Curve showing the distribution of wandering cells in Stage v, a. (v. Table I.) A, Anterior; P, rosterior. 

of transverse sections, we see that wandering cells are most abundant in the thoracic-abdominal- 
fold region and in that which answers to the future heart. We also notice the forward extension 
of migratory cells beyond the anterior edge of the optic lobes. In cut 12 the lateral extension 
of the nuclei on either side the embryo is well shown. The mouth is involved in section No. 28, 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 439 

and the embryonic area is iiutliuled liotweon sections 1-t and 11. The marked peripheral distri- 
bution of tlie niigratoiy cells is very significant. There seems to be a peneral movemeut of these 
bodies to all parts of the superlicies. 

What is the ultimate fate of those cells which wander out to the surface of the egg? Fig. 'M, 
VI. XXIX, represents part ol a sec^tion of theextraenibiyonic snrfac-e at this stage. Here is undoubted 
ectoblast (Ep.), aiul cells (V. V.), which have undoubtedly come from the yolk, are pressing against 
the surface. In a single egg one may meet with twenty or more such cells, as well as with cells 
in various degrees of ]iroxiinity to the surface. Do these cells (Fig. .'>4, Y. C) eventually (contrib- 
ute to the mesoblast or ectoblast of the embryo? This question can uot be answered by direct 
observation, since it is clearly impossible to follow the fate of the individual cells. From all the 
evidence which I have gathered I conclude that the wandering cells give rise to mesoblast — muscles 
of body wall, connective tissue, and blood corpuscles, and, later, to the definitive entoblast lining 
of the midgut. The part which the primary yolk cells play can not be decided, nor can it be deter- 
mined whether degeneration is more characteristic of these elements than of the invagiuate wander- 
ing cells. 

In a lobster's egg at the delamination stage, equivalent to Stage il. Table I, I fiud 21.'5 nuclei 
present. Eleven of these belong to the yolk. Upwards of twenty, two of which are yolk cells, are 
in process of division. Of the eighteen superficial or peripheral cells which are in karyokinesis, 
two are dividing horizontally or delaminating. In the lobster the primary yolk cells degenerate, 
in part if not wholly, at a very early stage, as already stated. 

In the egg-nauplius phase it was noticed that wandering cells settle down upon the ectoblastic 
bands out of which the nervous system is subsequently developed (Fig. 127. Y. C). In this case 
also it is impossible to ascertain with certainty the fate of such cells. They might form ectoblast 
or mesoblast, but it is more probable that they contribute to the latter Layer only. 

It is evident that the history of the wandering cells is largely the history of the mesoblast 
and entoblast. The mesoblast,* where it has been studied in Decapods, as in Astacus, is found 
(54) to originate iu certain swollen cells in or near the anterior margin of the "blastopore" or 
pit. From this primary mesoderm cells are budded off, which extend forward in a more or less 
continuous sheet over the ectoderm. It is possible that in Alj)heus the wandering cells may serve 
as a means of a precocious development of the mesoblast and entoblast. In connection with this 
idea, it is interesting to recall the fact that in high temperatures of the tropics the develoiunental 
.stages are passed very rapidly. At Woods Holl, Mass., the late eggnauplius of the lobster, 
Homani.s americanux, is from fourteen to sixteen days old, while a similar stage is reached by 
Alpheus saulcyi at Nassau, N. P., in about seven days. 

VIII.— THE DEVELOPMENT OF THE NERVOUS SYSTEM. 

The nervous system can be referred back in the end)ryo to an early stage (Figs. .58, 62, G8), 
when V-shaped ectoblastic thickenings unite theoi>tic disks to the thoracic abdominal plate. The 
intervening space is gradually encroached upon until the optic disks are completely bridged by a 
dense shet't of ectoderm. There is an apparent concjresceuce of the limbs of the V, and in the egg- 
nauplius (IMs. XLI, XLII) these thickenings form a pair of more or less closely united cords, whiiili 
are separated on the middle line by a median longitudinal furrow. The .shallow furrow is forme<l 
by the swellings of ectoderm which correspond to the future ganglia, and extends from the supraoe- 
sophageal ganglia to the segment of the first maxilhe. 

The nervous system of the egg-nau[)lius is not dirterentiated from the general integument, and 
the ectoderm is still a single layer on the niiddle line in the maxillary region (Fig. 121), while at 
the base of the first pair of antenna- (Fig. IIG) it has the appearance of an elliptical i)late in trans- 
verse section. 



* Welilou, xvliOHe ii;i|ier ou tin- gtTiiiiiiiil layers in Cr.iiigoii li.is l)eeti referred to, says truly tliat tlie (liU'ereiice 
between inv,ai;inate(l cpUh in not sufficient to enal>le one to say that ecrtaiu cells are eudoderm and that others are 
mesoderm, but he desiijnates as eudoderm all cells which are derived from the inv.igination, and restricts the origin 
of the mesoderm to the lower layer cells of the ventral plate. Jndging from the evidence which has thns far been 
presented, the cells which be bas marked endoderm, lying against the embryo and near the folds of the appendages, 
are in my opinion to bo interpreted as mesoblast. The thoracic-abdominal thickening is composed of a pair of concave 
"neuro-musciilar" or ventral plates, which correspond loathe single plate described in Alpheus. 



440 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

The antennular ganglion is in close union with the optic ganglion and unites also with the 
antennal ganglion which lies along the sides of the stomod;Buui, extending slightly behind it. 

The histological difierentiation of the nervous elements is not very considerable at this stage. 
In the ectoblastic thickenings, out of which the nervous system is formed, we can distinguish three 
kinds of cells: (1) the superficial cells, (2) the central cells, and (3) the accessory cells which come 
from the yolk. These are best seen in a section of the antennular ganglion (Fig. 116). The outer 
cells (1), which form the integument, possess very large granular nuclei. Some of these, on either 
side of the middle line, can be distinguished beyond doubt as the nuclei of those large ganglion 
cells so characteristic of later stages (see Figs. UG, 147, 169, 170, 191, g. c). They possess a more 
or less definite cell body of a round or oval contour. In preparations this is fine grained and, like 
the nucleus, stains but feebly. The weak stain of the nucleus is due to its very line and loose 
chromatin reticulum. Karyokinetic figures attest to the multiplication of these cells (Fig. 191), and 
it is highly probable that they give rise to similar cells which occur in both larva and adult. But 
what is remarkable in the earlier stages is their enormous size and their peripheral position. 
Keichenbach calls attention to similar cells iu the embryo crayfish, which also arise from the outer 
layer of ectoderm cells and for a long time help to form the outer wall of the body. It is hardly 
probable, however, that these cells are relatively more highly differentiated in respect to their 
ultimate function than any of the surrounding cells which take part in the nervous system. The 
central cells (2) are the ordinary ganglion cells of the cortex which inclose the fibrous masses. 
They have smaller and less regular nuclei, which stain very heavily. Cell boundaries are entirely 
effaced, and the cell protoplasm is reduced to a minimum. The accessory cells (3) rest on the 
dorsal surface of the thickening, and represent indifferent or wandering cells derived from the 
yolk (Fig. 116, cts., PI. XLI, mes.). 1 am not prepared to say that any of the ultimate nervous 
cells are derived from tiiis source, but I am certain that cells migrate from the yolk and attach 
themselves to the ectoblastic thickening out of which the nervous system is formed, and that they 
multiply by indirect division. It is probable that the connective tissue sheaths of the nervous 
system may be due, to some extent at least, to such cells. The ectoblastic thickening is increased 
by the radial division of superficial cells and by the horizontal division of the deeper cells. 

In the larval and adult stages the large balls of fibrous substance, particularly those of the 
brain, are surrounded by a delicate cell layer or internal envelope. The nuclei are small and 
spindle-shaped and form an exceedingly thin sheet. It is ])ossible that this represents intrusive 
mesoblast, derived from the yolk. Reichenbach states very positively that in Astacus connective 
tissue cells are squeezed into the fiber balls and eventually surround them. I have no positive 
evidence to show that the cells in question are not of ectodermic origin, but the behavior of the 
wandering yolk cells renders it probable that they should rather be referred to the mesoblast of 
the embryo. 

The Punct-substanz of Leydig or fibrous substance is not present at this time, unless it is 
represented by a very delicate reticulum in the midst of the nerve cells of the ganglia of the first 
antennse on their dorsal surface next to the yolk. Degenerating cells (Fig. 114 s') occur in abun- 
dance close upon the optic ganglia and the ventral ectodermal thickening. 

It may be interesting to notice that the structure of the antennular ganglion (Fig. 116) is 
similar to that of the optic lobe. In either case there is a peripheral tier of cells possessing large 
granular nuclei, an inner layer with smaller nuclei, and an imperfect layer of investing cells. 

Passing to Stage vri (PI. XLiv) we find the nervous system still very rudimentary. The super- 
ficial cells, particulai'ly iu the region of the optic lobes and the antenuiB, have large nuclei, which 
can be seen iu the act of division, dividing both longitudinally, thus increasing the superficial 
area of the plate, and also tangentially, in this way adding to its thickness. The very intimate 
union of the optic ganglion (Fig. 132 G. L.) with the antennular ganglion (S. 0- 0.) is still very 
noticeable, and the delicate investment of these parts on the side of the yolk [mes.) is more 
marked. 

Punct substanz has definitely appeared in the supra-oesophageal ganglion where there is a 
marked transverse commissure, and can even be distinguished in the oesophageal commissures. 
It forms a very delicate protoplasmic reticulum, and there can be no doubt -that the fibrous sub- 
stance of this part of the nervous system arises as an outgrowth from the protoplasm of ectoderm 
cells. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 441 

The paiivtl structure of the ectodermal plate is well shown in the antennular ganglion on a 
ievel with the transverse eoniinissures, or even in front of this, where i)aired masses, with small, 
vleeply dyed niicU'l, are separated by a median slieet of nnicli larger and clearer cells. This may 
l)()ssibly corresiiond to the mittelstrang, referred to again. 

Shortly after this (Fig. 130) tlie ganglia are blo(!ked off by a series of snperficial constrictions. 
At least seventi-en sneh ganglionic segments can be connted, beginning with the oi)tic and snpra- 
a'sophageal ganglia and passing to the last abdominal segments. The ganglionic blocks are 
formed rapidly from llie front backward. The ganglia of the first antennae are now the most con- 
spicuous i)art of tiie nervous system, unless we accept the large optic ganglia. There is a broad, 
transver.se, fibrous commissure in the antennular segment, which is still more i)rominent at a little 
later iXM'iod (IM. XLVI), when eye pigment is forming. From this cominissurc longitudinal rods 
extend forwards and unite tlie brain witii tlie optic ganglia, wiiih' simihii' I'ods grow l)aekwai(l and 
form the fibrous axis of the circum-tesophageal commissures. 

The plane of section in Fig. 148 passesjust in front of tlie (esophagus and tiirough the roots 
of the first pair of antenine (A 1), whicli should appear in the drawing as continuous with tlie 
integument. The ganglionic cells, which are directed toward the appendages, represent the anten- 
nular nerves, and are more apparent in the following section. The antennular ganglion is both 
preoral and preantennal, lying in front of the first pair of antenna', which it supplies witli nerves. 

The brain and ventral nerve cord are now plainly separated from the hypodermis, and are 
bathed throughout their extent with blood plasma, in which numerous blood corpuscles are .seen 
floating at every point, (riant ganglion cells have become most conspicuous in the optic region 
and at the periphery of the brain next the hypodermis. 

The brain is partially divided in front next the optic ganglion by a delicate membrane, which 
forms a median superficial partition between its two halves. This is continuous, with a delicate 
envelope, whi(!h in some cases can be detected about the brain, and is like that which covers tlie 
optic ganglion and nervous .system generally. A similar non-cellular membrane at this time 
divides the retina from the optic ganglion, and is continuous with the (suticular .sheath of the 
latter. The- intercepting retinal membrane is directly continuous with the delicate basement 
membrane of the hypodermis. The cuticular sheaths of the nervous system are present in the 
embryo (Figs. l~u, 1G8 />»•.), the larva (Figs. 175, 17G), and the adult. It may not seem easy to 
harmonize tliis account with the view already taken that the watulering cells attach themselves 
to the nervous rudiments and form a delicate investment to them (Figs. 129, 131 mes.). Such 
is plainly the fate of some of the wandering cells, but the number of cells is proliably too small 
to form a continuous structure, and it is possible that the delicate membrane secreted by the 
ectoblast may serve as an accession to that formed by mesoblast. 

With respect to insects, Wheeler (G7) concludes that in Doryphora the "outer neurilemma'' 
is ectodermic rather than mesodermic in origin, since — 

Shortly atYor tlu> seiiaralioii ot'tlic nerve cord from the integumentary ectoderm, it slieds from its surface a deli- 
cate chiteuous cuticle simultaneously with the shedding of the tirst integumentary cuticle. This cuticle, which is 
separated from the siirfiri- nf ti'.' "iili^r neurilemma, and even from the surfaces of the main neural trunks, is after- 
wards .absorbed. 

At the time when the nervous system has com]>letely separated from the integument there is a 
slight ingrowth of ectoderm cells along the midventral line, most pronounced between the ganglia, 
antl the appearance of a corresponding constriction on the side next the yolk. In transverse sec- 
tion the nerve cord is somewhat hourglass-shaped. This may be due to a mechanical necessity, 
arising from a more rapid development of the nerve cells in the lateral masses than in the other 
parts. 

Ectoblast (rcUs dcrivt'il trom the integument appear to be infolded between ganglia (see Fig. 
157 — a thin sheet of cells, with spiinlhvshaped nuclei bending in between the last thoracic and 
first abdominal ganglion, in the lower right liand i)ortion of the figure), but these infohlings may 
be somewhat deceitful, since they are straightened, to some extent at least, with the growth of 
the alxlomen (Fig. I'iS, alt;/. I). On the ventral surface of the thoracic region (Fig. IfiS) si)indle- 
shaped nuclei are seen wedged between the nerve cords on the middle line. It is not, however, 
certain that these cells are ectoblastic, since the sternal blood sinus is already formed, to which 



442 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

blood cells have penetrated, and here eventually the sternal artery is developed. While the evi- 
dence is not conclusive, we have only to decide between the former conclusion — that the intrusive 
tissue is derived from the wandering cells, and is to be referred to mesoblast, or the view that it 
represents differentiated ectoblast. 

A general account of the structure of the nervous system of the larva is given in the first 
section. Further than this the details of development have not been followed. 

In comparing this account with that given by Keichenbach for the crayfish, Astacus fluviatilifi, 
there are numerous particulars in which there is no agreement, while in some important matters 
Te are in accord. 

I find in Alpheus the oral invagination occurring on a line drawn between the bases of the 
antennular buds, and I have a great many preparations of the eggs of the lobster. Homarus anieri- 
canuH, which show the earliest traces of the stomodteum. Before th?. first antenniB are folded, 
when they are distinguished as dense patches of cells, some eggs show the primitive mouth as a 
minute circular pit, lying nearly on a line drawn between the centers of these proliferating cell 
areas, but, so far as my observation goes, never distinctly in front of them. 

The-relative positions of the mouth and first pair of antennae shift very rapidly during the 
early period of their growth, which precedes the fully developed egguaui)lius condition. The 
pit elongates and becomes a transverse furrow, and by the time the first pair of auteniiie are 
clearly marked off" as rounded buds, and before the second pair are raised into folds, the mouth is 
still on a line with the first of these appendages. When the second anteuuie are elevated into 
folds the mouth is behind the buds of the first pair, or on a line between their posterior edges. 

Keichenbach (taf. ii, Fig. 7a, Lb.) describes and figures a cell thickening between the "Kop- 
flappen" of the crayfish embryo (Stage B), which he considers the beginning of the labrum. His " 
sections show that below this point a mass of ectodermic cells occurs, which is interpreted as the 
"Vordarmkeim." The mouth is not represented as appearing until the following egg-nauplius 
stage (Stage F. Corai)are Fig. 66 and p. 100, § 7, " Der Vorderdarm"), when it occupies a j)osition 
exactly comparable with that observed in the lobster. I therefore can not agree with Kingsley in 
saying that Keichenbach "has all the appendages at first distinctly postoral." While the posi- 
tion of the Crustacean appendages may have been primitively postoral, it may be questioned if 
in the higher Crustacea the first antennre ever arise behind the mouth invagination. 

Kingsley describes the position of the mouth in Crangon as distinctly postoral, but an inspec- 
tion of figure 11 of his paper, leaves some doubt as to whether he is not mistaken in this particular. 
A single rudimentary appendage, marked as the first antenna, is represented as occupying nearly 
the entire space between the optic disk and thoracic abdominal fold. This does not agree with 
my own preparations,* and since in Alpheus, Homarus, and Astacus the mouth does not appear 
until a dense stratum of cells carpets the intermediate space between the optic disks and lateral 
cords, there is some difticulty in interpreting the cluster of cells marked »», in Kingsley's paper, as 
the invagination of the mouth. t 

In Alpheus, Homarus, Astacus, and probably in Decapods generally, the ganglion of the first 
antenna cannot be said to be postoral, but its development begins nearly on a line with the 
invagination of the pi-imitive mouth. The ganglion of the second antenna is developed behind 
the primitive mouth, but gradually shifts forward with its appendage until it comes to lie, in the 
larva, considerably in front of the mouth. In this movement, the ganglion however outstrips the 
appendage. The ganglia of these two appendages unite to form the brain or supra oesophageal 
ganglion. The ganglion of the first pair of antennfe is constricted into two portions marked by 
an oblique, transverse line at the surface. The anterior of these parts Keichenbach calls the 

* I have preparations of the eggs of Crant/on vulgaris, in various stages of development, from ttie segmentation 
onward. In one egg, which is somewhat more advanced than that of figure 10 (SI), or than the Alpheus in Fig. M 
of this paper, the optic disks and ventral pl>ate are dense patches of cells. On either side of the ventral plate and in 
close relation to it there is a marked area of cell proliferation which represents the mandible. In the sp.ace between 
this and the antenna the nuclei are more scattered, but the kaiyokinetic figures show the activity of cell division. 
In a late nanplius stage the stomodiBum is on the middle line between the first and second antennae, and the anten- 
nular ganglion is segmented into two parts on each side, as shown for Alpheus in Fig. 110. 

tThis criticism is supported by Woldon's observ.ations on Crangon, who, with reference to this subject, says: 
"The first antennie .are evidently prteoral from the very earliest period at which the mouth is visible." Op. cit. 



MEMOIRS OF THE NATIONAL ACADEMY OF BGIENGES. 443 

"vordere Hirnanscliwellung" and the posterior the "Seitenanschwellnng," using the terms of 
Krieger and Dietl. These latter particulars accord with Kei(!lienl>acli's description of the craylisii. 
I have not, however, found that in Alpheua, behind the level of the first pair of antenniu, the lat- 
eral parts (Seiteustriiiige) divided up into three sections, lleichenbacli further states that in each 
segment a middle-strand invagination is found, while the ganglia of tlie fifth (first maxillary) seg- 
ment has a prominent median string. 

In Alpheus I find an undoubted median ingrowth of surface ectoj)last between the two nerve 
cords. This in all probability corresponds to the niittelstrang, and, as already stated, it is most 
marked at a stage just before or at the time of the first appearance of the eye pigment, when the 
ganglia are separating from the integument. It is seen between the successive segments of the 
ventral nerve cord, where a single cell or string of several cells appears to be wedged between the 
two cords which are entirely separated (compare Figs. 151, KJO). The iiuclei of these cells are 
elongate and perpendicular with the surface. ■ Tliey are derived by delamination from the sui)er- 
ficial ectoblast, as the karyokinetic figures of divl<ling cells clearly show. These ingrowths are 
most noticeable between the segments, and whether they form any part of the nervous system or 
not, 1 have been unable to determine. In insects the mittelstrang appears to take no part in the 
nervous system of the adult, but in the thoracic region it is converted into the chitenous furcic. 

According to Reichenbach the lower (esophageal ganglion in the crayfish is formed by the 
fusion of the ganglia of the fourth (mandibular) to the ninth (third maxillipedal) segments. This 
is probably true of Alpheus, as may be inferred from Fig. 196. 

With reference to the commissures, lieichenbach states his belief that the transverse commis- 
sures originate in the uui)aired fiber masses present in each ganglion, while the paired masses 
give rise to longitudinal commissures. In Alpheus there appear in successive segments behind 
the mouth a pair of punctsubstanz balls, one ball in each single gaiiglion. These extend foiward 
and backward, uniting the ganglia into chains and forming the longitudinal commissures. A little 
later the transverse commissures are formed by bridging the cords between the points occupied by 
the fiber-substance balls in the several ganglia. All these stages can be observed in the embryo 
shown in Fig. 139, but all do not appear in the drawing. 

The origin of the peripheral nervous system is beset with many dilliculties. It is often impossi- 
ble to distinguish developing nerves from rudimentary connective tissue and muscle, owing to the 
similarity of the nuclei of each. This is less true of muscles, which in some parts of the embryo, as 
in the carajtace, are clearly distinguishable. In view of this, Ueiciieubach found it difficult to say 
whether the nerves were budded off from the central nervous system, from other ectoderm, or from 
wandering mesoderm cells. He thinks, however, that since many structures like the optic gan- 
glion, the crystalline cone cells of the retina, etc., are early recognizable, the nervous system is 
generally in intimate connection with the other organs. So the appendages, the nervous system, 
and the nerves, which at first can not be distinguished from each other, are intimately connected 
from the start; so the eye and the ear ijre never separated from the (central nervous system. The 
separation of the central nervous system from the skin takes ]dace slowly, and the ectodermal 
thickenings in the early stages must conceal the rudiments of nerves and skin elements. It is 
difficult, he remarks, to understand the late connection of the midgut with the central nervous 
system and the scattered mesoderm cells which form the muscles, but he says, in conclusion : 

Bei der Unterschung der wmiderb.iren Entwickliingserscheiimntjen in der orj;iiniscIien WeU. abor diiinst sicli 
bei tieferer BetracUtuiig iramer wieder der (iodaiiko aiif, das8 man a<dion vom Pisten Stadiniii an eineiu iintrMiiibaren 
Gauzen gegeniibersteht. (iS4, p. 80.) 

This view of the intimate colonial relations of all the cells of the (Mubryo can not be disputed, 
since it follows from the common descent of all the somatic cells from the ovum. But the relation 
which the embryonic cells bear to each other as the uiulilferentiated ectoblast to inesoblast must 
be of a very diHiereut nature from that which exists between muscle fiber and nerve in tiie difier- 
entiated state. It seems more probable that the anion of the central nervous system with other 
organs by means of nerves is strictly a secondary one, and that the latter arise by budding, as in 
vertebrates, from the central ganglia. The only observations whi(;li I have made on the develop- 
ment of nerves (see section i) refer to those of the first and second antennsB (PI. LV, Figs. 
213-21G, n. ati., n. a. g.; PI. LVli, Fig. 243, n. au.). The antennular nerve, which sujjplies 



444 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

the ear, appears to arise as au outgrowth from the autennular fiber mass of the brain (Fig. 243, 
af.). It consists of a fibrous portion leading directly from the fiber mass of the brain and of 
soniewliat flattened, or spindle-shaped nuclei, which penetrate the cortex of nervous cells and are 
undoubtedly proliferated from them. Possibly the internal sheath is continued over the growing 
nerve. 

IX. —THE EYES. 

The eyes in Decapods consist of a pair of lateral compound eyes, which in the larva are 
mounted upon long stalks, a condition usually retained in the adult, and of a median ocellus. In 
the Alpheus family the compound eyes are nearly sessile and are completely hooded by the cara- 
pace. In the larva, however, the eyes are both naked and possess long, movable peduncles (see tlie 
inetaiuorphosis, PI. xxi). In Alpheus saidcyi the oi)tic stalks are reduced to a mere rudiment, and, 
though provided with muscles, they can possess but very slight power of movement. They meet 
on the middle line in front of the brain, over the roots of the first pair of antennse. The compound 
eyes face forwards and outwards at an angle of 45° with the mesial plane of the body. A median 
papilla projects from below the lateral eyes, bearing the pigmented ocellus (Figs. 20!», 210, of 
larva). Two small hairy tubercles, outgrowths of the integument, occur on the inner side of the 
optic stalk. 

Spence Bate (3) says that since the Alphei are frequently found in ooze and muddy bottoms, he 
is inclined to think that they burrow more extensively than the common shrimp, and that the 
carapace has become modified to protect the eyes on this account. This may be true, but the 
Squilhe, on the other hand, in which the burrowing habit is more characteristic, have undergone 
no such modification. 

THE MEDIAX EYE. 

The median " nauplius" eye persists in the adult Alpheus, and is probably functional to some 
extent as a visual organ. This is represented in Fig. 18, PI. xxii, where it is seen as a small 
conical papilla, lying between the basal joints of the antennnles, and at the roots of the compound 
eyes, very close upon the brain. This is the first instance I have noticed of the persistence of the 
nau])lius eye in the adult. 

The general position of the median eye of the first larva of Alpheus saulcyi is seen in Figs. 
209 and 210, and the minute structure in Fig. 197. The pigment takes the form of an inverted 
Greek capital upsilon (j). There is no lens. A coaguable fluid is present, which is probably 
blood plasma. Besides muscle-fibers and pigment-secreting cells, and the integumentary epithe- 
lium, these ectodermic nerve end (?) cells, which abound toward the center of the papilla, are 
continous backward into the cortical cells of the anterior fiber mass of the brain. 

The first trace of the frontal eye which I have noticed occurs in the tenth stage (Fig. 168), 
when a small number of cells developing black pigment (probably ectodermic) can be seen near 
the surface, on the middle line, next the anterior extremity of the brain,* 

GENERAL ANATOMY OP THE EYESTALK. 

The visual apparatus of the compound eye of a Crustacean consists ef three principal parts, 
the retina, the optic ganglion, and the optic nerve, uniting retiua with ganglion, in addition to a 
peduncle of nerve fibers, which jiuts the optic ganglion in communication with the brain. 'These 
parts are contained in the eyestalk or opthalmite. The eyestalks are covered with a cuticle 
secreted by the ectoderm like that over the rest of the body. This cuticle, which in some prawns 
like Steuopus is hard and armed with spines, is converted at the distal, hemispherical surface of 
the stalk into a transparent cornea. The ectoderm or hypodermis secretes a well defined basement 
membrane. This is continuous with the basement membrane of the retina, pointing clearly to the 
fact which development proves, that the retina is a differentiated portion of the hypodermis. 
Below the basal membrane we meet with blood vessels or sinuses, muscles which control the 
movements of the eyestalk, glands, connective tissue, ganglion cells, and fibrous substance. 



* While tliis iiipmoir was in press a short paper appeared in the (}uarlerhi Journal of Microscopical Science (January, 
189'2), " 0« tlie XaupHus Eye persislimj in some Dicapotls." hj Jtlarf^aret Robinson. Tbe median eye was oliserved in 
some eight different species of the Carididie, including the genera Palajuion, Hippolyte, Virbius, Crangon, and Pan- 
da! us. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 445 

Alpbeus iu the only genus in which I have I'ound gliinds in the eyestalk. These are most notice- 
able at the periijhoral parts of the stalk between the basement memhiane and the ganglia. Tliey 
are in reality i)arts of the green gland, which sends outgrowths from the bases of the second 
antennie into the antennules, the eyestalks, tlie labrum, and the whole front of the head, so a.s to 
completely envelope the brain. The histology of the glandular coeca is the san)e in all parts. 
They consist of a cubical epithelium, composed of very large cells, supported by a basement mem- 
brane. 

Near the coeca of the antenual gland comes a layer of very loose connective tissue. This is 
specially abuudaut below the basement membraue of the retina. It forms a continuous sheath 
for the optic ganglion, and is reflected over the ojitic peduncle and brain. 

By far the greater mass of tissues of the eyestalk belongs to the oi)tic gauglion. This is 
composed of ganglion cells (Pig. 187), nerve fibers, and the peculiar fibrous tissue variously 
called " Punct-substanz" or " Ball-substanz," aud "substance ponctuee." Viallanes, wlio has 
made very careful and detailed studies of the optic ganglia of Arthropods, uses the following 
terminology (Gl). He divides the optic ganglion into two parts, an external and au internal 
portion. The surface of the external region is covered by the limiting membrane of the eye. 
The external is united to the internal parts by a bundle of crossing fibers, the external chi- 
asma (Fig. 178, Oh. Ex.). This, according to Viallanes, conesponds to the center of the corneal 
surface, and cousequently to that of the limiting membraue of the eye. The internal portion 
between the external chiasm.a and the optic peduucle is composed of three principal masses of 
punct-substanz: (1) la masse meduUaire externe, (2) la masse medullaire interne, (3) la masse 
meduUaire terminale. The external medullary mass is united to the masse medullaire interne by 
an internal cliiasma, while a fibrous peduucle joins the internal medullary mass to the masse 
medullaire tenniuale. The nerve fibers which pass between retina aud ganglion, he calls the post, 
retinal fibers, aud designates as " optic nerve" the peduucle by which the optic ganglion is united to 
the brain. The distal mass of punct-substanz is styled lame ganglionnaiie,* which he divides into 
a nuclear layer (couche a noyaux), a molecular layer (couche moleculaire), aud a cellular layer 
(couche a cellules gaugliouuaires). 

The punct-substauz of the optic ganglion is thus divided into four principal masses (Figs. 17S, 
209). Without adhering closely to the rather cumbrous terminology of Viallanes, the parts of the 
nervous system contained in the eyestalk between the brain and retina may be designated as 
follows: Optic 'peduncle (optic uerve of Viallanes aud others) ; proximal segment (masse medullaire 
terminale); internal middle segment (masse medullaire interne); external middle segment (masse 
medullaire externe) ; distal segment (lame gangliounaire) ; optic nerce (couche des fibers post- 
r6tinieuues). 

GENERAL STROCTCRE OF TUK COMPOUN1> EYK. 

The transparent cornea is the secreted product of a specialized layer of the hypodermis, which 
was designated by Patten as the "corneal hyi)odermis" and later as the "corneagen "(.">(», 51). 
Beneath this lie several strata of dioptic and sensory cells, separated from the ganglion by a base- 
ment membrane, which is continuous with that of the general hyjjodermis of the eyestalk. The 
ommateum, or eye proper (including those parts which intervene between the coruea and basal 
membrane), is formed by the repetition of a highly specialized unit, the eyelet or ommatidium. The 
size, number, and arrangement of the ommatidia is characteristic of species or genera, but is subject 
to considerable variation in diftercnt individuals, and the shape and arrangement of tiie ommatidia 
may be very irregular iu dilfen-ut parts of the same eye. The ommatidia are ditlereutiated clusters 
of ectoderm cells. There is a single ommatidium for each lens or corneal facet. The number of 
cells composing tlie ommatidium is very uniform iu Decapods, .Stoniatoi)o(ls, and Schizopods, so far 
at least, as the most essential cells are concerned. They are aslollows: Cells of corneal hypo- 
dermis, 2; crystalline-cone cells, 1; outer pigmented reliuular cells, 2 ; inner pigmented retinular 
cells, 7 (functional); Accessory jiigmented cells — irregularly distributeil, both above and below 
the basement membrane. i>rol)ably of ectodermic origin. 



• Tlio lame };an>;liomiiiiro is callcil " Ketiiia Raii^tliim '" by ClaiiH, who regards it aa the true ivtiiia : "das untutcre 
Gaugliuu oiiticum " by Cairiore, aud " porioiiticum '' by HicksuD. 



446 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 

STKILTUEE OV TIIK' OMMATIDIUM. 

Both a lack of time autl of fresli material have pieveuted me from makiug as thorough a study 
of the structure of the ommatidium of Alpheus as I had wished. The followiug account is based 
eutirely upon sections : 

The corneal facet is strongly biconvex (Fig. 200), the convexity of the lower side being the 
greatest. Its shape is usually hexagonal, but may be tetragonal, or sometimes nearly circular 
(as iu A. heterooheiis). There are two corneal cells to each lens. A single ommatidium is shown 
in Fig. 200. As in all Decapods, the cone cells which underlie the corneageu are four in number. 
The four segments of the crystalline cone (Fig. 208), which are secreted on the inner sides of the 
latter cells, are always separated by delicate boundary lines. The cone is capped by a mass of 
protoplasm iu which the nuclei of the cone cells lie, although it is not always easy to distinguish 
them. This cap api)ears to be raised into a slight elevation which touches the center of the lens. 

Pigment cells invest the cone more or less completely according to the conditions under which 
the eye is examined. These are the retinular cells. In the larva, and probably in the adult also, 
there are two distal retinular cells {2)g- c PI. Liv), as Parker (48) designates them, and at least 
seven proximal retinular cells (>-tl.). Parker discovered in Homarus and several allied forms 
a rudimentary eighth cell belonging to the proximal series. This is present I believe, in Alpheus, 
although my sections do not show it with the same clearness that it can be demonstrated in Palje- 
monetes. The seven proximal retinular cells secrete on their inner sides the rhabdom or rhab- 
domeres. A transverse section of the rhabdom gives the i)eculiar seven-pronged figure shown in 
the drawing (Fig. 205). The cells appear as fused in section, but possibly they would separate 
with readiness if macerated. Unfortunately I had no fresh material to experiment with. The 
proximal retinular cells appear to penetrate the basement membrane, and they are continuous 
below it with nerve fibrils. As to their distal ends, I have seen no evidence that they extend out 
to meet the cornea. The retinular cells abound iu dark pigment. 

The accessory pigment cells secrete a peculiar pigment which is glistening 'white in reflected 
light and is amber color iu transmitted light. This maybe similar to the pigment of certain cells 
which occur beneath the cuticle of the larva of Decapods in vai'ious parts of the body. It is not 
dfecolorized when subject to the prolonged action of weak solutions of nitric acid, while the black 
pigment is completely removed. What I once regarded as chitiuous bodies (20-21) were fused 
masses of this pigment which had been treated with nitrife acid. These cells penetrate the base- 
ment membraue, beneath which there is a considerable mass of both yellow and black pigment. 
The trains of cells which accompany nerve fibrils into the fibrous portions of the optic ganglia also 
contain granules of black pigment. The uumber of accessory pigment cells belonging to each 
ommatidium is indeterminate. They have the power of free movement or migration outward from 
the basemeut membrane and the power of retraction like the retinular cells. In Fig. 200 they are 
seen widely ditt'used, while tljere is a zone of black pigment cells (the pigment withdrawn by acid) 
enveloping nearly the entire cone and the distal end of the rhabdom. In an eye taken from a prawn 
which had just moulted, the yellow pigment was restricted to a narrow zone uext the basement 
membrane. Outside of this belt the retinular cells were colorless nearly up to the proximal ends 
of the cones, while the cones themselves were drai)ed iu black. 

AKKANGEMENT OF THE OMMATIDIA. 

In Alplieus saulcyi the ommatidia are arranged in a hexagonal system, subject to variations 
in difl'erent parts of the eye.* In the central parts of the cornea the facets are symmetrical hexa- 
gons. On the lower side of the eye the rows are more irregular and individual facets tend to 
become square and rounded. Toward the outer side of the eye the facets are very nearly square, 
next to these they become irregular and rounded, and on the extreme outer edge the facets are 
sometimes hexagoiuil. There is probably considerable individual variation. 1 have examined the 
cornea iu four other species of Alpheus, namely in Alpheus heterocheUs, A. minor, A. normani, and 
a West Indian species closely allied to A. heterocheUs. These cases attbrd some very interesting 



* For a stuily of the cornea, ailiilts of the largest size were selected and the cuticle was cleaned by boiling in a, 
concentrated solution of potassic hydrate. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 447 

facts iu connection with the arrangement of ooimatidia. In Alpbeus normaiii the facets are jren- 
eraliy symmetrical hexaj^ons, two of the sides beinj,' (|uite short. These tend to run into sqnaies 
or rounded areas at parts of the periphery. Alplicus minor has the facets in tiie lower part of the 
eye either of the hexagonal or some polygonal form, while in the upper and outer parts the facets 
are perfect squares. These blend on all sides into symmetrical hexagons. The first transition 
from the hexagon to the s(iuare is seen on the outer edges of this area where the individual facets 
become more and more rhomboidal, as the two opposite sides of the liexagon are more and more 
reduced. Finally these sides disai)pear and the facets become rectangular. The square facets of 
any given row now lie opposite to those of the adjoining rows. Four facets belonging to any two 
rows meet at a common point. In passing, however, from the area of scjuare facets to the periph- 
eral parts, the facets, though square, are out of line. Starting from a jioint where the facets of a 
given row are both tetragonal and opposite those of adjoining rows, and following the line over 
the hemispherical surface toward the perii)hery, the facets of this row soon tend to become alter- 
nate with those of the row next to it. A facet of the .second row lies slightly in front of the cor- 
responding facet of the first row. The facet of the third row lies a little iu advance of this and so 
on until the hexagonal shape is gradually assumed. 

In the Bahaman variety of Alpheun heterochelix the facets in the larval eye are markedly hex- 
agonal. In the adult there is the same curious transition from the hexagon to the square as we 
have noticed in Alpheus minor, only it is here, much more striking. In the peripheral parts of the 
eye, especially in the lower and inner jiortions, the facets are generally hexagonal. In the upper 
half of the eye between the center and periphery there is a small area of square facets. In Alplieus 
heterochel is the facts are characterized by much greater looseness of arrangement, there being 
large interlenticular si)aces. The facets are squares with rounded corners. In some parts of the 
eye, as on the inner lower side, the facets of the adjoining rows lie o|)posite each other. In other 
parts they regularly alternate and show a tendency to become hexagonal. At the periphery the 
facets are widely separated and circular.* 

The markings on the corneal lenses generally consist of a small central spot which is slightly 
elongated and strongly refracts the light. It ai)pears in section to represent a .slight depression. 
In the lobster, as first shown by Parker, there is a faint diagonal band which intersects a central 
hazy spot and divides the scpiare into equal triangles. These diagonal bands are all parallel in 
adjoining rows. In Alphem sanlvyi the elongated spots, if continued across the lens, would form 
a series of similar diagonal lines, but none such as these could be detected. In Alplieus heterochelis 
the markings are very constant and peculiar. In the center of the lens there is a large irregular 
impression from which numerous rays extend on all sides. The latter do not always reach the 
periphery. They appear like grooves in the substance of the lens. In the older embryo (Fig. 1!)4) 
the apex of the cone cells seems to touch the under side of the lens in certain ])arts of the eye. It 
is therefore possible that these cells remain in contact with the cornea and the interference thus 
caused gives rise to the spot. A similar explanation is offered by Parker to account for the con- 
ditions found in the lobster. The significance of the radiating lines seen in Alphcus heterochelis I 
have not determined. 

Iu Homarus the facets are square and grouped with remarkable regularity up to the very 
edge of the cornea, excepting at a point on the upper side, wbere a peninsula of tough cuticle juts 
in from the surface of the stalk and interrupts the elliptical jet black area of the surface of the 
eye. About this process, particularly iu front of it, the facets are hexagonal or irregular and very 
much smaller. 

Parker (4S) states that in the lobster " the ommatidia rearrange themselves between the times 
when the young auimal is 1 inch and 8 inches long. During this period the ommatidia increase 
about ten times in length and about five times iu breadth.'' I find that this rearrangement begins 
at a much earlier period, iu fact in the older larval stages. My examination comprised the follow- 
ing stages : (1) Length 8-9'""' (first larval stage) ; (2) length 11""" (fourth larva) ; (3) length 15.3'"'" 
(sixth larval stage) ; (4) length 49'"'" (lobster 1 year old). ~ 



*A similar transition of the sqnaro into the hexagonal facet in the same eye occuru iu AstucuH. See Howub' 
Biological Atlas, Fig. 111. 



448 MEMOIRS OF THE NATIONAL ACADEMY OE SCIENCES. 

lu the first larva of both Homarus and Alpheus saulcyi I find that the facets are not ouly hex- 
agonal but tend also to be slightly rounded. In the larva 11""" long the lenses tend to become 
square toward the center of the cornea, while at the periphery they are smaller and generally hex- 
agonal. Occasionally, however (just in what part I did not ascertain), the peripheral facets tend 
strongly to the tetragonal arrangement. In the next case (larva 15.3""" long) the facets in the 
outer parts of the eye are small and symmetrical hexagons. Toward the center they become 
larger, nearly square, and there is considerable interlenticular space. 

In the yearling lobster the readjustment of the corneal lenses from the hexagonal to the tetrag- 
onal system has been eftected over the greater portion of the eye, but the transition is still ilhis- 
trated iu a very beautiful manner. The cuticular ingrowth or peninsula, already referred to, seen at 
the upper surface, is hook-shaped, bending backward. In the open angle iu front the retina is least 
dittereutiated. The corneal facets in this region are small and mostly hexagonal. Following the 
lines of facets as they curve outward and backward from this point over the convex surface of the 
eye, we see illustrated iu a very striking way the passage of the hexagon into the s(juare by the 
gradual reduction of the opposite sides. The sides which are sacrificed are the third and sixth, 
counting from the side which lies between two adjoining lenses of the same row. Over a consid- 
erable area the facets are not quite square and thus tend to alternate with those of adjoining rows. 
The gradual transitiou to the square is attended by a gradual increase iu size. In the narrow 
angle behind the peninsula, the area of the hexagonal facets is smaller. In all other parts of the 
periphery the facets are square up to the very edge, as iu the adult. The corneal lens iu an 8-inch 
lobster has about twice the area of that of the lobster one year old (length nearly 2 inches). 

After reviewing these details the diflicult question arises: What is the significance of this 
remarkable change, and how is it effected ? 

Parker (48), who has made a careful study of the arrangement of the ommatulia in difterent 
Crustaceans, recognizes two plans on which these organs are grouped, the hexagonal and the tetrag- 
onal. He says that " in the Brachyura, as well as in three families of the Macrura, the Hippidie, 
Pagurid;Tj, and Thalassinid;e, the arrangement of the ommatidia is invariably hexagonal. Iu the 
remaining macrurous Decapods the ommatidia are grouped on the tetragonal plan." There are, 
however, exceptions to the latter statement, some of which are mentioned. He regards the change 
from the hexagonal to the tetragonal system as apparently due to the increase in size aud the con- 
sequent crowding of the ommatidia, and reaches the conclusion from the various facts presented, 
that the hexagonal arrangement is phylogeuetically the oldest. Upon this view we should expect 
to find the eyes of the most highly differentiated of the Crustacea arranged ou the tetragonal sys- 
tem, whereas iu poiuts of fact the crabs, who are uotorious for their great activity and keen powers 
of vision, permanently adopt the hexagonal arrangement. The lower Macrura adopt both methods, 
and in certain species of Alpheus, as Alpheux minor, which are active in habit and show no trace of 
degeneracy, the change is begun but not coni])leted iu the same retina. In order of time the hex- 
agonal prism precedes the square prism and the conditions which determine the permanency of 
each of these systems in the adult life of the individual are undoubtedly inherited, but they do not 
appear to have a phylogenetic significance, at least I do not see the way clear to an explanation 
upon this ground. 

Taking, for example, the lobster and the crab, in each case the larval eye represents, we must 
believe, the more generalized type, the adult eye the more specialized type. The larval eye of both 
Macrouran and Brachyourau has the hexagoual facet. We may safely conclude that this Js a 
lU'imitive arrangement. The adult crab, which has a more highly organized nervous system aud 
keener senses, retains this primitive ari-angemeut, while the lobster, whose senses are without 
doubt duller, departs from the type, and in the adult the facets of tlie cornea take on a permanent 
tetragonal shape. The conditions which we would naturally look for are thus reversed iu these 
two forms. 

We must assume that the change iu the case of the lobster is a useful variation, that it is in 
some way subservient to keen vision, otherwise it could never, upon the theory of natural selection, 
have secured such a permanent characteristic footing. On the other hand we must believe that 
the hexagoual facet puts the eye of the crab into better harmony with its environment than the 
square facet would do, for if the eye had not been in harmony with external conditions it must 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 449 

have varied aiul iittaitied t« a new 8triictiire duriug the course of the evolution of tiie Brachjoiira 
from Macrourau ancestors. 

Many crabs like the saatl crab, Ocypoda arenaria, spend a good portion of time out of 
the water and their eyes are admirably adapted for vision in the air, as in tiic case of this species, 
wiiicli will detect any moving object, such as a man or a dog, a long tlistance oil'. We might thus 
hope to find a way of escape from the ditticulty in the diversity of habits in the two forms, the 
lobster being exclusively an aquatic animal. But the ])rimitive Crustacea must have all been 
aquatic, and the hermit crabs, some of which spend all or nearly all of their time in the water, 
agree with the Bracliyoura in having a corneal membrane comiiosed of hexagonal facets, not to 
speak of other Macrourau forms which are invariably aquatic, like Al|)lieus, in which the hexagonal 
system is retained or there is a transitional conditi<m between the hexagon and the square in the 
eye of the adult. 

We do not yet know the physical or physiological signiticance of these two kinds of facets, 
and possibly in this fact lies the root of the difficulty pointed out above. 

The hexagonal arrangement is the natural one. lor tubes with elastic walls <o assume when 
there is sufficient mutual pressure, and it is also the most economical arrangement, so far as wall 
Space is concerned, for regular prisms of equal capacity. Next to this in point of economy of wall 
space comes the square prism, and next to this the triangular prism, where, as before, all available 
space is occupied. This last arrangement, however, is not regularly assumed. 

If a given number of hexagonal prisms occupying a given space tend to increase in size, then 
they would tend also to assume another form less economical of wall space, such as the square 
prism. If the wall area of the hexagonal jirism remains the same and the number of prisms 
increases in a given space, then each prism must be less economical of wall area and assume 
another form like that of the square prism. 

If we nmy apply the same principles to the growing ommatidia, it is possible that crowding 
may have something to do with the change. 

In the h)bster the change from the hexagonal to the tetragonal system is attended by a growth 
of the ommatidium in all directions and by the addition of new ommatidia. If an outline drawing 
of the eye of the first larva of the lobster be compareil with a similar one of the fifth larva, it will 
be seen that the convexity of the outer surface, that is, the area of the eye, has very greatly 
increased, whereas the diameter of the eye stalk has remained very nearly the same. During 
this period the change from the hexagon to the square has been begun. During this time the 
ommatidia have increased in length with the increasing convexity of the cornea, and they have also 
increased in sectional area and in actual number. It is a very noticeable fact also that in the 
lobster the eye stalk is compressed dorso-ventrally, so that the horizontal radius of curvature 
of the retinal surface is considerably greater than the vertical radius of curvature. Furthermore, 
the sides of the hexagonal facets which suffer reduction lie in a vertical plane, indicating a strain 
or pressun^ iu a dorso-veutral direction. 

in Alphtus miulvj/i the relative increase in the convexity of the corneal cuticula is very slight 
in passing from the first larva (length, about i""") to later stages, and the eye of an adult (i;i""" 
long) is only about one-fourth larger than that of the larva at the time of hatching. Moreover, in 
Alj)heus the convex surface of the eye is nearly a jjerfect hemisphere, the curvatures being the 
same in every plane. 

If we examine the eyes of a crab in a similar way we find that the area of the surface of the 
retina increases less rapidly in passing from the zoiia to the megalops stage than in the case of 
the lobster in going from the first to the fourth larval forms. The comparison, however, is of little 
value since the lobster has an abbreviated develojiment. The eye stalk of the adult crab jiresents 
a large retinal surface, but it pioserves a nearly cylindrical (orm, although the radii of (curvature of 
the retinal surface are very une<]ual. In the hermit crab (in a single speeie^s examined) the hexag- 
onal arrangement is i)reserved, not, however, without indications of a ten«lency to become tetrag- 
onal, the hexagons becoming asymmetrical in certain parts of the eye. There is, however, the 
same compression of the eye stalk iu a dorso- ventral plane as we see in the lobster. 

It has seemed to me worth while to jioint out these facts as ottering .some suggestions to the 
problems under discussion, although I make no attempt at a mechanical explanation. 
S. Mis. 94 29- 



450 MEMOIRS OF THE I^ATIONAL ACADEMY OF SCIENCES. 

The primitive arraugeineiit of the oinmatidia was probably in the form of simple tubes or 
(■..ylinders, with spaces between them and with rounded or indefinite facets. Mutual pressure 
among these tubular eyelets, arising from any cause, produces the hexagonal arrangement, the 
most economical method so far *> wall space is concerned. Interferences snch as have been sug- 
•iested, as growth of individual oinmatidia or increase in the number of ommatidia in the same 
area, thus admitting a method of arrangement less economical of wall space, or the great increase 
in length of the ommatiilia and a relatively less increase iu width, attended by a progressive change 
of the hexagons into squares (the apparent slipping of the rows of facets on one another), may 
enter as factors into this change, but they do not suffice to explain all the conditions. It will be 
understood, of course, that there are no changes in the individual facets, these remaining in the 
same shape until they are cast off in the moult. The changes which the individual ommatidia 
undergo are very gradual, and since the number of cells for each ommatidium is constant and deter- 
mined at a very early period, excepting the accessory pigment cells, they must be attributed to 
the change in the size and relative positions of the cells themselves rather than to intussusception. 
It is possible that the change from the hexagon to the square is not produced in the same way in 
all cases and that the conditions of growth which bring about this result are far more compli- 
cated than would appear from the suggestions which have been made. A careful study of the 
arrangement of cells in the ommatidia of the eye of the young lobster during the period of transi- 
tion would possibly throw some light upou this interesting subject. 

THE DEVELOPMENT OF THE COMPOUND EYE. 

Five years ago (20) I stated my conviction that the compound eye of Alpheus, and probably 
also of Paliemontes and of the large Isopod, Ligea oceanica, originated from a thickening of the 
superficial ectoblast. The development of the eye iu Alpheus was more fully described in a pre- 
liminary notice (31). I will now recapitulate the main results, at the same time correcting such 
errors as I have detected. 

In studying the development of the eye the following are some of the subjects which present 
themselves for investigation: The origin and structure of the optic disks; the separation of the 
optic disks into a ganglionic and retinal portion by an intercepting basement membrane; the dif- 
ferentiation of the retina into ommatidia or eyelets; the dififerentiatiou of the optic ganglion and 
the development of the optic nerve, by means of which the sensorj^ end organs of the retina come 
iu direct relation with the ganglion. 

(1) Origin of the Optic Dish. — The optic disks (Fig. 58, PI. sxxir) consist of large ectodermic 
areas or patches on either side of the middle line. They are centers of rapid cell division, united 
by means of the lateral cords, which are bands of proliferating cells, with the thoracic-abdominal 
plate. 

So far as I am aware we have no account of the origin of the optic disk in any Decapod except- 
ing Alpheus, Astacus (54:), Crangon (.30), and Homarus (47\ Parker, in his careful studies on the 
eye of the lobster, was unable to obtain the earliest traces of the developing optic disk, and the 
accounts of Eeichenbach and Kingsley differ very materially. I will therefore describe somewhat 
in detail the process by which the optic disk is produced iu .llpheus. 

The optic disks at the time when they consist of a single stratum of cells are shown iu Figs. 
58, G8, and 69. A series of four transverse sections through the ceutr'al portion of the left optic 
disk is represented iu Figs. 64:-67. The posterior face of each section is presented, the series pass- 
ing from the front backward. 

Since it is from the optic disk that the eye and its ganglion are developed, the important inquiry 
which arises at this stage is, how is the change effected by which the disk passes from this single- 
layered to a many-layered condition like that seen in the egg nauplius (Figs. 107, 114)? If the 
eye represents a series of hypodermal pits, it would be reasonable to look for some trace of these 
infoldiugs in the embryo. If, on the other hand, the compound eye of the higher Crustacea rei)re- 
seiits a closed vesicle produced by a single invagination of the hypodermis, of the type seen in the 
protfltracheate Peripatus, we should expect to find some trace of an involution at this stage. So tlie 
answer to this question may have an important bearing upon the phylogeny of the compound eye. 

Cell boundaries are easily discernible at the surface, but it is evident that the nuclei do not 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 451 

all lie at the same Ii-vel. Passing now to Stage IV (Fig. 72), we notice several important changes 
iu the external api)earauce of the optic disks. They have approached nearer the iniildle line; 
they have increased in area; their nuclei are more crowded ; near the center of the disk and on 
the side of it toward the middle line (Fig. 7L', C. M.) the nuclei are distinctly larger. In inter- 
preting these changes we must resort to sections and a careful study of dividing nuclei. A com- 
plete series of consecutive transverse sections through the- left optic disk at this critical stage is 
given iu PI. xxxv. The last of the series cuts the rudiment of the first antenna. Karyokinetic 
figures come to our aid in pointing out the way in which the growtii of the disk is eflectcd. Tiie 
nuclei divide either radially, the plane of division, clearly marked by the equatorial plate, being 
perpendicular to the surface, or horizontally, the plate being in this case parallel with the 
surface. In a single I'isk at this stage there were eight cells undergoing radial division. Of 
these, six were near the periphery, where the cells formed a single stratum, while two were near 
the center, where the disk was slightly thickened (Fig. 8(t, G. M.). It is evident from this and 
similar cases that the increase iu area of the disk is accomplished by radial cell division. The 
same is true of all jjroliferating areas in the lateral cords, where the appendages are soon budded. 

In the area marked ('. M. (Fig. 80) the optic disk is no longer a single layer. This thickening 
is due either to horizontal cell division, that is, delaniination, or to emigration. The appearances 
of emigration are often very deceitful, bu t I think we may safely conclude that the initial thick- 
ening of the optic disk in the proliferating area, marked C. ^I. (Figs. 80, 90), is due to emigration, 
that a solid ingrowth akin to invagination takes place at this point. Thus the cell marked ec in 
Fig. 80 is distinctly below the surlVice. The boundaries of the cell can be clearly seen. The cell 
ec in Fig. 90 (dotted line should be extended), on the other hand, is clearly iu contact with the 
surface by a slender protoplasmic jjrocess, while the nucleus lies at a much lower level. I inter- 
pret the latter as a cell at the point of breaking all connection with the surface and migrating to a 
lower position. In the lirst instance this has already been accorapWshed. 

Iu the stages under discussion there are one or two cases out of a large number of sections 
involving the optic disks of several individuals, which probably indicate delaniination in the 
peripheral parts. At a later jieriod (Figs. 102-107) the nuclear figures are conclusive. In one 
instance (Fig. 102, ec.) two cells are seen delaminating side by side. The thickening of the optic 
disk is thus due in part to delaniination, apd this process is i>robably supplemented by emigration, 
at least in the central area. The central area represents in all probability the " optic invagination" 
of the crayfish, and is concerned solely with the production of the optic ganglion. In Aliiheus 
there is a proliferating area simply, but no superficial depression or invagination in the strict 
sense. 

It is noticeable that in Stage iii (PI. xxxiii) wandering cells, or cells which travel through the 
yolk, have not appeared in the neighborhood of the optic disks. In Stage TV (Fig. 70, Y. C.) they are 
' not far away, and in later stages (Fig. 91) these cells are close upon the disks. Some of them which 
enter this region, coming near to or uniting with the disks, undoubtedly degenerate (coniiiare 1'. C, 
Fig. 94, .s-.s'. Figs. 95, 90, 99, 100). Some of the cells of the disks next the yolk elongate, and appear 
to form a somewhat transitory covering. As already suggested, these bodies are probaVily derived 
from the wandering cells. 

The various stages by which the disk, already described, is converted into a conspicuous, 
lobular mass of cells in closest relation with the antennular ganglion such as we have in the egg- 
nauplius (Fig. Ill, 0. L), can be seen by reference to the plates (Pis. xxxvi-XL). 

(2) The Development of the Retina and Optic Ganglion. — The next event of importance is the 
differentiation of the optic disk into ganglionic and retinal portions. This is already begun iu 
Stage VII. A deeper layer from which the ganglion is developed ( Figs. 129, 132, G. L.) is gradually 
separated from a sniierticial tier of cells with very large nuclei {OE). This layer is the retinogen. 
The differentiation begins in the lateral lower halves of the optic disks and extends upwards and 
toward the middle line. As the <lisk s[irca(ls outwards, and at the same time increa.ses iu thick- 
ness, it tends to overgrow the hyi)oilermis and becomes raised into a lobe or fold. The optic lobe 
(Figs. 136, 138) thus repre.sents a thickening of the hypodermis. It is covered next the yolk by a 
delicate basement membrane (-Bm.), which is continuous with that of the surrounding hypodermis. 



452 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

Wauderiug cells are seen in contact with tbis inetnbraue (Fig. 13(5), Vmt they prohahly do not 
share in its secretion, although they occur in the closest relations with it. 

At a little later period (Fig. 138) the retinal portion is several cells thick on the outer edges 
of the lobe, while it is a single stratum iu the sagittal section, shown in Fig. 138. The plane of 
section is near the center of the lobe. The deeper nuclei of the ganglion are large and clear, the~ 
outer are smaller and stain more intensely. This section can be clearly understood if compared 
with the transverse section, Fig. 146. We see that the optic ganglion is here divided into an 
external or distal part and an internal or proximal portion liy a thin sheet of very large and clear 
ganglion cells. Parker (47) describes and figures an exactly similar structure iu the lobster, and 
1 fully agree with him in regarding this band of nuclei as representing similar bauds, which 
Keichenbach (Taf xii. Figs. 173, 174,^4. \V. I. ]V.) describes in the crayfish. In Keichenbach's 
plates these nuclei apjiear as a nariow fold, forming the lining of what is describetl as a secondary 
optic invagination. 

Three iiuiict-substanz mas-ses have already appeared in the inner iialfof the optic ganglion 
the external middle segment, which lies next to the band of large nuclei, and the internal middle 
and proximal segments. The proximal medullary mass is much the largest and is the first to be 
differentiated, although the others follow close u])on it. The dividing nuclear band lasts but a 
short time, and in Stage 10 (Fig. 107) has disappeared. In front of it is developed the lame gang- 
lionaire or distal segment of the optic ganglion. This has an outer convex surface which is con- 
centric with the basal membrane and with the outer surface of the retina, and it is carpeted by a 
special layer of ectoderm cells. These apiiear in section as a single row of elongated nuclei. 

In an early communication (20) I stated my belief that the puuct-substanz arose from a 
metamorphosis of ganglion cells. This view was suggested by certain appearances presented 
by the large clear nuclei, more particularly by those of the dividing band in the optic glangliou 
(see Fig. ISO). Kingsley (3l'),came to the same conclusion in regard to certain large clear nuclei 
iu or near the distal segment of the optic ganglion of Crangon. In reviewing this subject more 
carefully I am convinced that this interpretation is erroneous. These large clear cells are iu 
reality undei'going indirect cell division, as proved by the karyokinetic figures which are occa- 
sionally seen. Both tbe chromatin network and the chromosomes are exceedingly delicate, and 
when the section is in the plane of the equatorial plate an appearance is presented which under 
certain conditions of staining and preparation might easily be interpreted in favor of retrogressive 
metamorphosis. I conclude that the punct-substauz of the nervous centers is in all cases derived 
from the protoplasm of cells, not from cell nuclei. 

In Stage ix when eye j)igment first appears, the structure of the retina is very simple. By 
the transverse section (Fig. 146), we see that the retina consists of a thickened ectoderm plate, 
thickest in its deeper portions; thinning out toward the middle line at the surface. It has the 
shape of the half section of a concavo convex lens. 

In Pahemonetes the structure of the eye is i)recisely similar at this stage. Fig. 189 gives a 
section of the eye of this prawn, on a line with the oesophagus behind the optic ganglion, where 
it is seen to rest against the yolk. The black pigment, though appearing to arise in connection 
with certain inesoderinic cells (wandering cells from the yolk), it in reality belongs to deep ectoderm, 
and marks the retinular cells. The cell protoplasm bearing the pigment bodies grows outward 
(Fig. 146), and also pierces and extends some distance below the basement membrane (Figs. 191, 
]92). The latter is a delicate cuticular structure secreted by the ectoderm cells which lie along 
the line of division of retina and ganglion, and continuous with the baseu)ent membrane of the 
hypodermis. In some sections it appears to be duplex, a condition described for the eye of 
the lobster by Parker (47), iu which the inner layer enfolds the optic ganglion. The wide ojien 
fissure which now exists l)etweeii retina and ganglion (seen in transverse .section at au, Fig. 136) 
is partially tilled with yolk. There is not the slightest doubt that cells enter this fissure from 
the yolk (Mes. Fig.s. 146, 167, 189, 194, etc.), but what the fate of these wandering bodies i.s, I find 
it very difficult to decide. I think, however, that it can be stated definitely that none of the.se 
cells enter the retinogen. They mast supply .some of the pigment found in this region, or they 
may become converted into connective tissue. In Stage x (Fig. 167) the yellow accessory pig- 
ment cells are clearly diflerentiated, or at least the pigmeut which these bodies give rise to, is seen 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 453 

in abiuiilance around the retinular elements. This is without doubt ectodennic iu origin. Some 
yellow pigment also occurs below the basement membrane. This may be ectodennic or meso- 
dermic, but tlu' great bulk, if not all the accessory pigment cells, which in the adult eye extend 
their processes through the basement membrane, are ectodermic in their origin. 

At the edge of the retinal i)late the cells become very much elongated (Figs. 146, 1.S8), and 
tinaily can no longer be distinguished from the superficial ectoderm. The thicliening of the retinal 
plate is due solely to emigration. This might be inferreil by the iiiterwedging of the nuclei (Figs. 
188, 180), and it is jiroved in cases of cell division by the position of the equatorial plate, which is 
always perpendicular to the surface.* 

A later stag<! in the develoi)meiit of the eye is illustrated by I'Mgs. 190 and 191, which are 
anterior (superficial) and jtosterior (deep) transverse sections. In Fig. 190 we see the retina differ- 
entiated into cell clusters. Each cluster represents part of an ommatidium — the corneal hypo- 
dermis, the cone cells, and possibly the distal retinular cells. The lower stratum of small nuclei 
belongs to the proximal retinube and to the accessorj' pigment cells. In deeper section, Fig. 191, 
we distinguish the proximal retinuhe — black, rod-shaped bodies piercing the basal membrane. 
The nuclei lie at the distal extremity of the pigment. Between the pigmented parts of the retinular 
cells other nuclei occur, which possibly represent an eighth rudimentary retinular cell (rtl^). At the 
surface of the eye there is a stratum of cells with elongated nuclei. These are the nuclei of the cor- 
neal cells and probably also of the distal retinula". Between this and the inner stratum of retinular 
nuclei, the nuclei of the cone cells are seen, and a granular substance which is probably the first 
trace of the peculiar secretion of these cells. In an older stage represented by the drawing (Fig. 
192) we see all these parts iu a higher degree of development, and the eye has grown out into a 
very prominent lobe. Fig. 167 is intermediate between this and Fig. 191. The central parts of 
this eye are the most highly developed, and as we pass to the periphery especially away from the 
middle line, the ommatidia are less and less developed, until they reach the condition of a single 
layer of unditfereutiated ectoderm. Thus, in a single section (like Fig. 192), we have a sort of com- 
posite picture of the various stages through which the developing retina has passed. 

A considerably older stage is reached in Fig. 191. The cells of the corneal hypodermis are 
quite large and have already secreted a cuticular lens. The nuclei of the cone-mother cells are 
also conspicuous. 

Later still, when the embryo is nearly ready to hatch, the eye has undergone very slight 
change. Fig. 187 represents an oblique longitudinal section through the eye stalk of Alpheus 
heteroclielis. The black jiiguient of the retinular cells has been removed by the action of the nitric 
acid. Irregular sheets and masses of yellow pigment occur both above and below the basement 
membrane. The conspicuous stratum of nuclei, iu which the bases of the cone cells are embedded, 
belong to the proximal retinular cells. The nuclei (unrepresented) lie close to the surface between 
the corneal cells. The cone cells einl distally in a conical caj) of i)rotoplasm, the apex of which 
touches, in some cases at least, the corneal facet. The proximal ends of the conte cells taper gradu- 
ally and can not be traced below the pigment zone. 

In the first larva of Alpheus saulcyi the structure of the eye is similar. This is illustrated in 
Figs. 201-201 and Fig. 209. In transverse section (Fig. 201) the corneal cells are crescent-shaped. 
The distal retinuhe lie in the same plane with the latter and hav^e the peculiar arrangement shown 
in the drawing. They are grouped in pairs, so that each set of corneal cells is surrounded by 
six nuclei — two pairs of nuclei and two single nuclei. The two odd nuclei jtertaiu to the omma- 
tidium in question. The delicate membranes which appear to surround the corneal cells belong, 
in all probability, to the distal retinular cells. 

The structure of th<^ <;ompound eye has become a favorite subject of research during the i»ast 
five years, and the important study of the development of the faceted eye, about which very little 
was known when Balfour's "Comparative Embryology" appeared, has not been neglected; still 
much work needs yet to be done in this direction. The literature of this subject has been recently 
examined by Parker (48), and 1 will therefore add to this account only a few comparative notes. 

•Parker states that tho corneal hypodermis arises in the lobster by simple delaminatioo. {Op. cit.) I have 
never seen delamiuutiu^ cells iu any part of the retina of Alpheus or Pahemonetos. 



454 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

The proliferating areas iu the optic disks of Alpbeus aud Hoinarus are uudoubte<ll.v homologous, 
and jirobably correspond also to the optic invaginations described in Astacus by Reichenbach and 
in Crangou by Kingsley. I therefore agree with Parker (47) in interpreting the ingrowth or invo- 
lution of cctoderui, whichever may occur in the developing disk, as concerned with the optic gan- 
glion solely and not v.ith the retina, Reichenbach describes the visual organs as originating from 
three factors: (1) an epidermal layer; (2) the optic invagination; (3) the optic or segmental 
ganglion. From the epidermal layer and outer wall of the optic invagination the retina arises, 
while the inner wall of the secondary invagination unites with the optic ganglion. An inspection 
of Reichen bach's Fig. 224 (54) shows, as Parker has pointed out, that in all probability Eeichen- 
bacli has misinterpreted his sections, and that the entire retina is derived from the hypodermal 
layer. The layer of cells with elongated nuclei, which he has designated as rhabdom, clearly per- 
tains to the optic ganglion, and probably represents the nuclear covering of the distal convex 
surface of the lame ganglionaire (Fig. 192 of this work). 

Kingsley, in his third paper on Crangon, changes his interi^retation of the invagination of the 
optic disk of Crangon, regarding this involution as concerned only with the optic ganglion. I am 
inclined to believe that a renewed study of this subject would show that the optic disk originates 
iu Crangon precisely as it does iu Alpheus. A sei'ies of sections through the thickening disk of 
Crangon has little to show which is not brought out by a similar series of Alpheus (Figs. 76-83), 
and no pit or hollow invagination is seen. 

The independent origin of the optic ganglia lends some support to the view that they have a 
segmental value and are not merely outgrowths from the brain, that the eyestalk is a modified 
appendage containing its proper ganglia. 

Watase's interesting views (63) concerning the origin of the ommatidium from a hyijodermal 
pit do not receive the support we should expect from embryology. How much value is to be given 
to the embryological data in this case it is hard to say, but, seeing the persistence of the involu- 
tions in the eye of Limulus, we would expect to find a trace of similar infoldings in the developing 
eye of the lower Crustacea, provided their eyes are constructed upon the same type. Until greater 
evidence is furnished I am inclined to regard the "compound eye" not as an aggregate of simple 
eyes, as the name implies, each one of which is due to a hypodermal infolding, but rather, as Par- 
ker has suggested, to differentiated clusters of ectoderm cells originating from a single epithelial 
layer. 

THK KYE UNDER THE INFLUENCE OF LIGHT AND DAUKNES8. 

In June, 1890, while enjoying the facilities for biological research afforded by the labora- 
tory of the U. S. Fish Commission at Woods HoU, Mass., it occurred to me that some valuable 
experiments could be made by testing the effects of direct sunlight and total darkness upon the 
gi'owth and behavior of the pigment cells of the compound eye of Crustacea. After finishing my 
experiments upon one form I learned of the experimental work of Exner* upon the eyes of the 
glowworm, Lampyris splendidula, of Hydrophilus, Dysticus, and Colymbetes, iu which he records 
the same phenomenon in insects which I have observed in a Crustacean. Later a paper has also 
appeared, by Mademoiselle M. Stephauowska, ou the histological arrangement of pigment iu the 
eye of Arthropods. I have seen only an abstract of this work, from which I gather that it deals 
either largely or entirely with the eyes of insects. My experiments were made upon the common 
prawn, Pakvmonetes vulgaris. 

A dark chamber was constructed and rendered as absolutelj^ light-proof as possible. Inside 
of this a small glass aquarium was so arranged that a stieam of sea water could be kept run- 
ning through it for any length of time. Thi'ee egg-bearing females were then placed in the 
aquarium and the chamber was sealed. The egg embryos were early nauplius stages. Females 
with eggs in a similar stage were also kept under observation in an aquarium exposed to the light. 
The general cast of color of the prawn taken in the light is some shade of light brown or brownish 
green. After spending eighteen days in the dark, the prawns were taken out aud exposed to the 
moderately bright light of the laboratory. The eyes were jet black and appeared to have greatly 



* Since these notes were writteu I bave received the completed work of Exner, Die Physiologie der Facettirten 
Augin roll Krebseii uiid Instcleii, iu which the field of esperinieut ia greatly enlarged. 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 455 

ssvelled in size, iind the liody was bleached nearly white. The peculiar appearance of the eyes irax 
cauficd 1)1/ the I'orirard extension of the distal retinidar cells, of which there is a single pair in each 
ommatidium. 

The e^ius of some of tiie inawiis were batching, and the pij^ment of the zoea was carefully 
compared with that of the tirst larva of Paheuiouetes batched in the li^ht. IJolli the black pigment 
of the letiniilar cells and the yellowisb green pigment of tbe accessory pigment cells of the eye 
and tbe large brown cbromatopbores in different i)arts of tbe body were of tbe same cbai-acter, 
whether tbe embryo bad develoi)ed in darkness or light. 

Another prawn was kept in tbe dark thirty-eight days, and on exposure to the light it pre- 
sented the same ai)pearance. As in the other cases, as soon as light reached the eye tbe distal 
retiuube began to retreat to a deeper level. At tirst the black i)igment which characterizes these 
cells extends out to the cornea. After an exposure of two minutes to direct sunlight a slight 
transparent baud is seen below tbe cornea. This light zone increases as the i)igment continues its 
retreat until, in tbe course of three-quarters of an hour, tbe distal retinubu ensbeatb only the 
lower ends of tbe cones. 

In another experiment a prawn was left only about twenty-four hours in darkness. Tbe same 
effects were produced in tbe eye, which assumed its former condition after being iu tbe diffused 
light of tbe room twenty-tive minutes. Tbe distal retinular cells thus respond very ))romptly to 
tbe action of tbe light, and in tbe course of a few hours (tbe exact time needed was not determined), 
if excluded from tbe light, completely enshroud tbe proximal ends of tbe cone cells. 

In the eye of Pahemonetes, taken in ordinary daylight, there are three distinctly marked strata 
of pigment between tbe basement membrane and the cornea, a proximal narrow stratum of yellow- 
ish brown i)igment belonging to tbe accessory pigment cells; a wider and mucb lighter area 
peppered with dark granules, pertaining to tbe proximal retinular cells, tbe nuclei of wbicb form 
a conspicuous belt or layer on a level with tbe distal extremity of tbe rhabdoms. Lying close 
upon the tier of retinular nuclei is a thin stratum of intensely black pigment, composed of the distal 
retinular cells. As stated above, there are two of these cells to each ommatidiun), and they each 
send out a slender thread-like process, which extends in some cases as far forward as tbe corneal 
cuticula, where it is ])ossibly attached. I have not detected any similar prolongations in the direc- 
tion of tbe basement membrane. Below the level of the cone, which terminates abruptly in a 
convex proximal surface, the cone cells are prolonged into a long slender stalk consisting of proto- 
plasm or of a refractive substance of a different nature from the cone. The cone cells are not 
apparently prolonged below the level of the retinular nuclei. Tbe distal retinular cells thus sur- 
round the proximal ends of the cone cells. 

In tbe eye exposed for thirty-eight days iu the dark tbe distal retinular cells form a stratum 
about midway between tbe corneal cuticula and tbe layer of nuclei of tbe proximal retinular cells. 
The nuclei occupy a central position in this layer. Pigmented pseudopodia extend forward to tbe 
cornea, and occasionally a cell shows a slight inward prolongation. Had the eyes been preserved 
without bringing them into the light, even for a moment, tbe distal retinular cells would undoubt- 
edly have occupied a still more peripheral position. 

In tbe eye kei)t in the darkness for tbe same length of time and afterwards exposed to the 
light for live hours the distal retinular cells have retreated until they lie around the proximal 
ends of the cones. The nuclei of these cells lie immediately upon the nuclei of the proximal retin- 
ular cells, and it is interesting to notice tbe pigmented body of each cell folded on itself. In 
section tbe pigment takes tbe form of plaited black ribbons. When tbe eye is again stimulated 
by light tbe ribbon unfolds as the cell travels forward. 

These cells are called by Exner tbe iris pigment, since they regulate the brightness of the 
retinal image iu much the same way as the vertebrate iris does. 

X. — SUMMARY. 

In the review, including Sections v-ix of Part Second of this memoir, the i)rincipal embryo- 
logical facts have been summarized, and it will now suflBce to recapitulate only some of tbe more 
interesting results. 



4:1)6 MEMOIRS OF TEIE NATIONAL ACADEMT OF SCIENCES. 



Metamorphosis.— [1) The inajority of the Alpbei hat(;h as zoea-like larvre, while two species are 
known, A. hetfirnchelis and A. sanlcyi, in which the metanioiphosis is abbreviated. This shortening 
of the inetainorpiiosis appears to be directly related to the habits and environment of the Sjiecies. 
.4. lu'terocheiis Jias one metamorphosis al- Beaufort, Nortli Carolina, a more abbreviated develop- 
ment at Key West, Florida, and, it we are right in considering the Bahamau torni as a member of 
this species, at Nassau, New Providence, the metamorphosis is complete or unabbreviated. The 
Nassau form ot Alpheits saulci/i either has the metamorphosis greatly abridged or it hatches with 
all the external characters and the instincts of the adult. When we inquire into the modes 
of life of these species we find the remarkable fact that the Nassau Alpheus saulcyi is a ))arasite or 
commensal, living in the pores of certain sjionges, and the metamor[)hosis is completely absent or 
profoundly modified. The Floridian Alpheus heterovhdi-s is a parasite in si)onges, and iias its 
metamorphosis greatly abridged. Tlie Beaufort heterochelis, which must be regarded as descended 
from the Floridian stock, has its metamori)hosis less abridged than in the latter case and it is 
nonparasitic. However, we still find it occasionally producing small eggs, indicating a tendency 
to revert to the old metamorphosis, long since abandoned. Even if we decide that the Nassau 
hetcrochelis has bad a rlifferent genealogy from that of the Beaufort variety, we still have strong 
evidence to show that the metamorphosis of the species may change in accordance with a change 
in habits and environment. 

Varintion and Habits. — (i!) Alpheus heterochelis of Beaufort presents an interesting variation 
in the structure of the small chela, which appears to be a sexual one. 

(3) In many Macroura as well as Bracbyoura, and especially in the Alpheus, one of the claws 
IS enormously enlarged, often nearly equal in size to the rest of the body of the animal. This great 
chela may be either on the right or left side of the body, but it almost invariably follows that all 
the young of a brood have the large claw on the same side, indicating that this characteristic is 
inherited from the parents, and that where both of the latter have the right or left claw enlarged 
they give rise to right and left handed broods, respectively. 

(4) Alpheiis saulcyi presents very j>rofound variations, and some of these varieties would 
undoubtedly be regarded as distinct si)ecies by systematic zoologists if the intermediate forms 
were unknown. These forms are described and discussed in Sectious v and Yii of Part First. 

Species living side by side show no tendency to commingle, and hence we conclude that the 
striking varieties which we are here met with are not the re.sult of hybridism, but are confiued 
to a single species. Two well marked varieties occur, which I have distinguished as Alpheus 
saulcyi, var. brevicarpus, and A. saulcyi, var. longicarpus. Between these forms every intermediate 
stage is found. 

The color variations in this species are also exceptionally marked. In all respects the males 
appear to be more variable than the females. The structural peculiarities of the mother appear 
to a large extent in the oUspring, aud if the swamping eflects of intercrossing should be elimi- 
nated it is likely that this species would soon become separated into at least two distinct forms. 

It seems most probable that the change in habits or environment which this species has under 
gone, lias acted as a direct stimulus to variation. 



Structure of the Larva of Alpheus saulcyi. — (o) The structure of the first larva of this Alpheus 
reaches a very high degree of complexity, wliich is but little exceeded by that of the mature adult 
foriii. 

The green gland does not yet appear to have an external opening. The five pairs of gills 
present at this time are also iiidinientary, and the rei)roductive organs are only represented by a 
small cluster of large cells on either side of the middle line, between the digestive tract and the 
anterior end of the heart. For the histological details, reference must be made to Section I or 
Part Second. 

The Ovary and Ovuriun Eyy. — (<i) The ovary consists of an external stroma of muscular and 
connective tissue and a lining epithelium. The ova arise from the lining epithelium, and each egg 



MEMOIRS OF THE NATIONAL AOADKMV OF SCIENCES. 457 

is differeiitiiited lioiii a distinct epitlielial cell, the nucleus of the cell lieconiiii;>: tlu" nucleus or 
geiininal vesicle of tlie egn. Some of the epitlielial cells euwiap the (leveIo[)in;; ovum and form 
the follicle or pocket in which it is lodged. The chorion or inner egg membrane is the direct 
secretion product of the fullicular (U'lls. 

(7) In Ilomarus and I'alinurus the character of the germinal epithelium is somewhat <lifferent 
from that of Alpheus. The outline of individual cells is obscured and the germinal epithelium 
extends inward from the wall, i)i the form of radial sheets or folds, between which are rei-ntrant 
blood vessels. There aie a number of germogenal areas corres])on(ling to the folds in which the 
ova originate. During growth the eggs gradually pass from the center toward the perii»hery. 
In the germogen the cell outlines are obscured.* 

(8) The yolk arises within the cell protop|asm, and in Homarus degenerating nuclei occur in 
the ovarian stroma, and it is probable that a certain number of nuclei degenerate and enter into 
the food yolk of the egg. In the lobster also some of the follicle cells develop into gland like struc- 
tures which chara<-terize the mature ovary. They appear to have a dire<'t relation to the growing 
eggs, but their true significance has not yet been ascertained. In about two weeks after the eggs 
have been extruded these structures have almost wholly disappeared. 

(9) I have observed a single ]<olar body in a sec.lion of the egg of Stenoi)US, in which the male 
and female i)ronuclei were present, and two ]>olar bfidies in the ripe nncxtruded egg of the lob- 
ster. In lobster's eggs also which failed of extrusion at the proi)er time, an<l which eventually 
degenerate in the ovary, I find that the nucleus is at the surface. It has the appearance of a 
female pronucleus. It is thus probable that the polar bodies are often, if not always, given oft' 
before the eggs are laid, t 

Segmentation in Alpheun minor. — (10) The segmentation in Alpheux minor is in some respects 
anomalous, and the conclusion seems to be warranted that we have here a case of amitosis, unlike 
anything wlii(;li has been hitherto described in Crustacea. Unfortunately my material is not at 
present suflicient to enable lue to say in exactly what way the usual i)roce8s of cell division has 
here been uio<litied. 

Delamination . — (II) The segmentation has been thoroughly reviewed in Section v, and 
it is unnecessary to repeat the details. I wish to call attention, however, to the fact that at 
the close of segmentation in the lobster .some of the blastodermic cells delaminate ami their 
products pass into the yolk. In Alpheim snulcyi a similar migration of cells from the sui>crticial to' 
the deeper ))arts of the egg occurs, but in this case it was not determined whether this migration 
was preceded by delamination or not. These cells api>ear to originate in greatest number over 
that side of the egg which corresponds in position to the embryonic area. It seems i)ossiblc that 
these cells may represent a primitive endoderm, the function of which has been usurjied. In the 
lobster they speedily degenerate. 

Invagination tStage. — (12) The invagination stage, which soon follows, results in the admis- 
sion of more cells into the yolk and in the formation of an organ called in this n\emoir the ventral 
or thoracic-abdominal i)late. Cells also continue to i)ass into the yolk from the ventral plate. 
While cells are constantly being subtractcil from the ])late, it is <!onstantly receiving new recruits 
from the surface, owing to the activity of cell division in this region. We thus have in Alpheus 
a multitude of migrating (tells, derived originally from three .sources: from the blastoderm, from 
the cells which are first invaginated, and from those which originate later from the ventral ]>late, 
after all trace of the superficial pit has (lisai)pcared. 

Oerm-laycrs. — (13) The.se migrating cells, which are collectively called "the wamlering cells" 
in Section vii, spread to all parts of the egg. While it is i)erfectly obvious that these bodies 
represent mesodennic and cnd()(b'rmi<! tissues, it is not so easy to determine what i)articui;ir cells 
give rise to this or that layer, nor iS it easy to decide in many ca.ses, from a superficial study, wliether 
migrating cells may not be derived from the ectoderm in various parts of the embryo. This sub- 



*The structure of the ovary of the lobster Las been recently described by Uunipus in a detailed pai)er upon the 
embryology of this species. Ho has culled .itteution to the folded character of thi! ovarian epitludiiiin, which is so 
marked in the young or immature ovary. (The Embryology of the Americau Lobster, by Hcniioii Carey linnipus, 
Jourii. of ilorplioloijij, Vol. v, No. 2, 1891.) 

t Polar bodies have beeu recently described in the external eggs of the lobster by Bunipus. Op. cit. 



458 MEMoms OF the national academy of sciences. 

ject is fully considered in Section tii, the general results being : (1) That it is not possible to 
decide what part the primary yolk cells play in Al^jhens, for reasons which have been already 
considered; (2) that the great bulk of the cells which migrate forward from the area of invagina- 
tion and attach themselves to the embryo, or proceed to the peripheral parts of the egg and take 
up a position at the surface, are undoubted mesoblastic elements ; (3) tliat those cells which give 
rise to the eudodermal epithelium in the egg uauplius are derived largely from cells which migrate 
in a posterior direction from the area of invagination ; (4) that degeneration, followed by the death 
and dissolution of the chromatin and cell protoplasm, is characteristic of the wandering cells at 
about the beginning of the egg-nauplius iJeriod. The mesoblast has become a well-recoguized 
layer before the endodermal epithelium has appeared. 

(14) The egg, with centrally moving cells whi(;h have budded from the blastoderm, may be 
compared with the j>Z««Mia stage of Cffileuterates, and the internal cells may represent the primi- 
tive eudoderm. According to this view, the invagination stage has no reference to an adult 
gastrula-like ancestor, but is a purely secondary condition, which became so impressed upon the 
ancestors of the present Decapods that it has remained in their ontogeny. 

In the majority of Decapods which have been studied the invagination has no direct relation 
to the mouth or anus, or to the alimentary tract. The conditions which are present in the cray- 
fish cannot be regarded as typical or primitive. 

(15) in Alpbeus and Homarus the primitive mouth arises on a line between the rudiments of 
the first pair of antenna, but these appendages are never jjost-oral. The hind gut originates as a 
nearly solid ingrowth, apparently at a point considerably behind the position of the pit due to the 
first invagination, and is formed one or two days later than the mouth. 

Cell, dissolution. — (16) The degeneration of embryonic cells is treated at length in Section vi. 
It is remarkable that the early segmentation stages of Aljyheus minor are attended with the degen- 
eration of protophism. The chromatin residues remain for some time in the yolk, and eagerly 
react upon dyes, but gradually lose this power and eventually enter into the general nutrition. 

(17) Degenerating cells appear in greatest force in Alpheus, Astacus, and Homarus at about 
the egg-nauplius stage, and from that time their numbers begin to wane. They appear in one 
instance before the differeutiation of the germinal layers, and are not confined to any one layer at 
a later period, but in Alpheus scntlcyi they are most characteristic of the wandering cells, which 
repi'esent mesoderm and endoderm. The "secoudary mesoderm cells " and " white-yolk elements" 
which have been described by Keicheubach, are to be regarded as degenerating cells. Degenera- 
ting cells also occur in connection with the " dorsal phite." 

The Eyes, — (18) The details of the structure and development of the eyes and nervous system 
are fully reviewed in Sections Tin and ix. 

The eyes and optic glanglia are derived from the optic disk, in the formation of which there is 
in Alpheus no proper invagination. The thickening of the disk is accomplished by emigration 
from the surface and by the delamination of superficial cells. An area of active cell division can be 
distinguished, which corresponds to the invagiuate area of the optic disk of the crayfish. The 
cells which migrate from the center give rise to the rudiment of the optic ganglion. The disk 
grows out in the form of a lobe, and becomes differentiated into an outer retinal layer and an inner 
ganglionic layer. The eye proper is differentiated from the retinogeu, which is primitively a single 
layer of ectodermic cells. 

(19) I am inclined to regard the "compound eye" not as an aggregate of simple eyes, as its 
name implies, each of which is due to a hypodermal infolding, but rather as a collection of differ- 
entiated clusters of ectoderm cells, originating in a single epithelial layer. 

(20) The absence of light has no appreciable effect on the development of the eye pigment, 
but in Palwmonetes the distal retiunlar cells respond very promptly to the action of light. If the 
light is excluded from the eye, these cells migrate outward and enshroud the proximal ends of the 
cones, sending out pseudopodal prolongations to the cornea. When the eye is again stimulated by 
light the pigment immediately retreats from the surface, and the cell takes the form of a plaited 
black ribbon, leaving the cones free. 

Adelbert College, , 



MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 459 

XI. — REFEEENOES. 

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herichte. Bd. ii, pp. 312-318. 1875. 

7. Brooks, W. K. The Metamorposis of Alpheus. .fohns Hopkins University Circulars, iio. 17. 1882. 

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11. BuLLAii, J. F. On the Development of Parasitic Isopoda. Phil. Trans. Roy. Soc, Vol. CLXix, pp. 505-561, Pis. 

XLV-XLVII. 1878. 

12. Cl.\i;s, C. Untersuchungeu iiber die Orijaaisatiou u. Eatwickelung von Branchipus uiid Artemia, nebst ver- 

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15. Erdl, M. P. Eutwickluug des Hummereies vou den ersten Verjinderiiugen im Dotter an bis zur lieife des 

Embryo, pp. i-x, 11-40, Taf. i-iv. Miiuchen, 1843. 

16. Faxox, Walter. On some Younn' Stages in the Development of Uinpa, Porcellana, and Pinnixa. Bull. Mus. 

Comn. Zool., Vol. V, No. 11, pp. 253-268, Pis. i-v. 1879. 

17. . On the Development of /Vi?rt'«ione(e« rit^iyari*. iJ«/7. .l/ic. f'oiHjj. Zoo/., A'ol. v, pp. 303-330, Pis. i-iv. 1879. 

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20. Hekrick, F. H. Notes on the Embryology of Alpheus and other Crustacea, aud on the Development of the 

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22. . Tlie Abbreviated Metamorphosis of Alpheus and its Relation to the Conditions of Life. Johus Hopkins 

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23. . The Roproductivo Organs and Early Stages of Development of the American Lobster. Johns Hopkins 

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25. Howell, W. H. The Life-History of the formed Elements of the Blood, especially the red blood Corpuscles. 

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29. KiNGSLEY, J. S. A Synopsis of the North American Species of the Genus Alpheus. Bull, of the U. S. Geol. and 

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Pis. i-u. Salem, July, 1886. 



460 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

32. . The Developuitiut of Craugou Vulgaris. Third paper. Bull. Essex Iiial., Vol. xxi, Nos. 1-3, pp. 1-42, 

Pis. i-ui. 188i). 

33. KriegkU, K. K. Ueber das Ceutraliiervensystcm des Flusskrebses. Zeit. f. loiss. Zuol., B. xxxiii, pp. 1-70, Taf. 

xxxi-xxxiii. 1879. 

34. LKJ5E1IINSKI, J. Einige UutersuchiiUKen iiber die Entwicklnngsgeschichte (ler Siekrubben. BioL Ceiit'hll., B. X, 

Nos. 5 and 0, pp. 178-l«o. 1890. 
Sri. Lekeboullet, a. Eeoherches siir le Mode de Fixation des CEufs aux fausses patte.s abdoojinales daus lesEcrevisses. 

Ann. de Sci. Nut., IV S(^r., T. 14, pp. 359-378, 1 PI. 1860. 
30. . Iteoherches d'Embryologio Comparoe siir le D(5velopperueut du Brochet, de la Purche et di; I'Ecn^visse. 

Mem. pres. par divers Savants h I'Acad. des Sci. de I'Inst. Impt'r. de France, T. 17, pp. 447-80.'), Pis. 1-fi. 

Paris, 1862. 

37. LocY, W. A. Observations on the Development of Agelena uaevia. Bull. Mua. Comp. Zool., Vol. xii, No. 3, pp. 

63-103, Pis. 1-12. 1886. 

38. LUDWlii, a. Ueber die Eibildiing im Thierreiche. Arbeit, aus dem zoolog.-zootom. Inst, in Wlirzbnrg, B. I, pp. 

287-.'')10, Taf. XIII-XV. 1874. 

39. Mayer, Paul. Ziir Entwickluugsgeschichte der Dekapoden. Jeuaisrhe Zeit. Natiirwiss, B. XI, pp. ls8-209, Taf. 

XIII-XV. 1877. 
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21-23, Figs. 1-8, V Jahrg. 1882. 

41. MouGAN, T. H. A Contribution to the Embryolog.y and Pliylogeny of the Pycnogonids. Studies from Biol. LaVy 

of the Johns Hopkins Uiiimrsity, pp. 1-76, Pis. i-viii. Baltimore, January, 1891. 

42. MiiLLEU, Fritz. Pahemou Potiuua. Ein Beispeil abgekiirzter Verwaudlung. Zool. Anz., No. 58, pp. 1.^2-157. 

1880. 

43. . Berichtigung, die Verwandhing des Palaiuion Potiuua betretfend. 2oo/. ^nJ., No. .55, p. 233. 1880. 

44. NuSBAUM, Joseph. L'Embryologie d'Ouiscus murarius. Zool. Am., No. 228, pp. 455-458. 1886. 

45. . L'Embryologie de Mysis Charmeleo. Arch, de Zool. &jje>. (sf G(?«eraJe, 2d Ser., T. 15, Nos. 1-2, pp. 123-202, 

Pis. I-Xli. 1887. 

46. PiCKAKn, A. S. Notes on the Eaily Larval Stages of the Fiddler Crab and of Alpheus. Amer. Xutnralist, \(>\. 

XV, pp. 784-7B9, Figs. 1881. 

47. Parker, G. H. The Histology and Development of the Eye in the Lobster. Bull. Miis. Comp. Zool., Vol. XX, No. 

1, pp. 1-62, 4 Pis. 1890. 

48. . The Compound Eye in Crustaceans. Bull. ilus. Comp. Zool., Vol. xxi, No. 2, pp. 45-140, 10 Pis. 1891 

49. Pattkx, Wilt.iam. The Develoiunent of Phryganids, with a Preliminary Note ou the Development of Blatta 

Germanica. Quart. Journ. Micros. Sci., Vol. xxiv. New Ser., pp. .549-602, Pis. xxxvi A, B, C. 1884. 

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1886. 

51. . Studies on the Eyes of Arthropods. I. Development of the Eyes of Vespa, with observations on the 

Ocelli of .some Insects. Journ. of Morpholotjij, Vol. I, pp. 193-227, 1 PI. 1887. 
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53. . Zur Entwickolungsge-schicbte der Dekapoden. J™7iiD..f. i^Tadtryesc/i., B. vi, pp. 241-249. 1840. 

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des Sci. Nat. Zool. et Pal^ontol. 



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*'~- ■ Elndi's liisti)li«j;ii|iii'« ft nrijiniologitiiicn Hiir li'.s centrcH niTvirix ct Ics iii;;:nn'8 den seriH (lea aiiiiiiiiiix 

iirliciiIf^M. CiiKiniimo Mpiiioiro. I. L«CVrvi)aii dii Criiniet {(Jidiiwda ciri'iilmceiw el ralopliiiii.i HuIUuh). 
U. (:<)in|niiaiHoii iln cervoaii dcs rriistar(i» «t lies iusectcN. HI. Lo cerveaii ct la iiKiiplidlojjio du 
mHieli'tto cci>lialir|iie. Ann. des Sci. Nat., Zoid. et Pjilr=oiitol., T. iv., Nos. 1-1!, VII Ser., pp. l-l-.'(l, I'Ih. 
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kitiK riiiremiln, Vol. iv, pp. ■^■^7-:;:'. I, 7 Pis. 1890. 

t>4. \\ Ai.DKYKU, \V. EiiTNtoi'k iiud Ki. 

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s 



APPENDIX r. 

THE LIFE HISTORY OF STENOPUS. 

Siuce thi.s paper wa.s written Cliiiu has ilescribed (Die rtelagische Thierwelt in grosseren Jleere- 
steefen, Bihliotkeea ZDologica, i, 1888) a small transparent crnstaceaii wiiii-li he iralis Meicmia 
darigna. It oeeurs at the surface and also at various depths down to (iO(> M. A comparison of 
his description and tiguie (Taf. iv, Fig. 6) with the Stenopus larva shown in Pis. ix and x of this 
memoir shows that Chun's Meiersia clavigna is undoiilitedly a Steuo|>us larva, a little older than 
the one shown in PI. x. ( W. K. B.) 

It is suggested at the bottom of page 310 that the cement by which the eggs are fastened to 
the abdomen may possibly come from the oviducts. According to recent observations of (Jano 
(Mittheil Zool. ^f(if. XrapoL, ix, 1S!M ; abstract in Joxni. Roy. Mir. SoV., No. .S3, 18»1) this is 
derived from cement glands situated iu Steuopus under the epidermis of the [deopods. It is 
thought by Cano that these glands, to which the secondary egg membrane is due, are modified 
glands of the appendages, and that the cement substance may serve as the medium llirough which 
spermatozoa reai;h the ova. In order to reach the eggs the sperm cells jirobably pass throu-h 
pores in the chorion. 

This paiier was written in the summer of 1888, befoje I had seen the report of Speiiee I}ate ou 
the Challenger .Macrura (IJeport on the Crustacea Macrura dredged by II. JI. S. Challenger lUiiiug 
the years 1873-'76, Zoology, "N'ol. XXIV, p. 209, PI. xxx, 1888). The Challenger brought home 
only two specimens of titcnopus hi.spiilux, one from Kandavu, P'iji Islands, and one from IJermnda. 
Spen<!(^ Bate says that Steuopus has been "chiefly recorded from the eastern seas and the shores 
of India by Desmarest, Milne-Edwards, and Sir Walter Eliott; from Japan by de Haan." It has 
been thought that ,SV/((i7/rt greenlaniJiea of Keba, which apjiears under several names, may be the 
same as Stenopus hispithm. "The genus," says Bate, "thus apiiears to inhabit regions so widely 
ai)art as Greenland in tlie north, the Bermudas and Mediterranean in the west, and the soutlteru 
coasts of India and the Fiji Islands in the east. It has been found in the cold waters of the Arctic 
regions as well as in the warm shallow waters of the tropics, but, desjute this cosmoiK)litau range, 
it has not been recordeil as having existed in any geological formation." 

While the conclusion that the Arctic form is a Stenojms may be correct, it seems highly im- 
probable that it is specifically related to ,Stenojm.s hMpiilH.s. There is no evidence at least to show 
that this is the case. 

liate figures a late egg embryo of Steuopus (Fig. 40, p. 211i), and erroneously concludes that 
the animal has a short metamorphosis and that it hatches as a " Megalopa." He also gives a <lraw- 
ing (PI. xxix, Fig. 2, v.) of the lirst larva of Spongiola reniisla (a prawn which is plained by Bate in 
the family Stenopida'). This is clearly not a zoea, hut n protozoea, as is better shown by the sketch 
of the recently hatcheil larva (Fig. 42, p. 210) by von Willemoes Suhm, and the strong resem- 
blance which it bears to the protozoea of Steuopus hisjndus is very striking (compare with PI. vil, 
Fig. 11, of this paper). 



462 MEMOIRS OF THE NATIUXAL ACADEMY OF SCIENCES. 

According to Bate the braucbial formula of Stenopus was first elucidated by Huxley iu his 
memoir on the classification of crayfishes (Proc. Zool. See, London, 1878). There are six pleuro- 
branchiie; eleven arthrobranchiae, fiv'e of which are anterior and six posterior; one podobranchia, 
and six mastigobranchi*, of which the first is the only efficient appendage. 

Sjjence Bate states that after careful comparisons he failed to find specific differences between 
specimens from the Eastern and Western Hemispheres. 

EREATA. 

As numerous errors have unavoidably occurred in this paper, I will correct the more important 
of them. 

Page 341, liue 8, for -'PI. vii " read PI. x. 

Page 341, liue 13, for '• Lcsnenr" read Lesuenr. 

Page 343, line 2, for " cells have spread more rapidly at a given point ou the egg" read cells have increased more 
rapidly over a given area of the egg. 

Page 343, over table for " Tennperature 80° F.," read Teuiperatuve of air, 80° F. 

Page 344, lines 11, 16, 31, 32, and 47, for " Fig. 10" read Fig. 11. 

Page 344, line 18, for " largely developed " read highly developed. 

Page 345, lino 20, for "Fig. 10" read Fig. 11. 

Page 345, line 30, for "Fig. 11 " read Fig. 10. 

P.age 345, line 38, for "the first and second niaxillipeds" read the second and third maxillipeds. 

Page 346, line 31, for " larger than telsou " read longer than telson. 

Page 347, line 16, for " xii and Fig. 4U " read xiii and Fig. 3a. 

Page 347, line 29, for "and 38" read and 39. 

Page 347, lines 37 .and 41, for " PI. xi" read PI. xii. 

Page 347, line 40, for " Figs. 43, 45" read Figs. 43, 44. 

Page 347, line 47, for " Fig. 47 " read Fig. 46. 

Page 348, liue 15, ohiit "erriuem larve." 

Page 348, for lines 32-34 read: Body nearly cylindrical; tergal surface covered with spines. Carapace witli 
promiueiit laterally compressed rostrum and distinct cervical and branchio-cardiac grooves. Outer antennse with 
long bristle-bonlered scale bent under the inner antennse toward the middle liue. Second maxillipeds with setjg- 
erous lamina, attached to endopodite. 

Page 348, line 46, for " a marked transverse fossa " read a marked cervical groove. 

Pairo 348, last line, for " transverse furrow" read cervical or mandibular groove. 

Page 349, line 17, for " Fig. 40 " read Fig. 39. 

Pa^e 349, line 21, for " their inner borders which meet iu the middle line" read the inner borders of the exopo- 
dites which meet in front. 

Page 349, line 23, for " Fig. 39" read Fig. 38. 

Page 349, line 25, for "Fig. .38" read Fig. .36. 

Page 349, line 39, for " Fig. 48" read Fig. 45. 

Page 349, seventh line from bottom, for "the great chela? " read bearing the great chel*. 

Page 3.50, first liue, for " Fig. 48 " read Fig. 47. 

Page 350, first and second lines, for "bearing a shorter proximal one below" read bearing a longer tooth and a 
shorter proximal one below. 

Page 3.50, line 9, for "Fig. 41 " read Fig. 40. 
« Page 3.50, table, tenth line from bottom, for " Length of chela" read Length of chela of same. 

Page 352, liue 10, for "hartschiilig" read hertschalig. 

Page 352, tenth liue from bottom, for "Crustacos, Arachnidses" read Crustac^s, Arachnides. 



APPENDIX II. 

PARASITIC FUNGUS IN THE EGG EMBRYOS OF ALPHEUS SAUICYI. 

The remarkable parasite of Alpheus saidcyi, to which allusion was made in Part First of the 
Memoir on the development of Alpheus, is illustrated in Fig. 199, PL liii. Although a large num- 
ber of egg-bearing females were examined and their eggs were sectioned, only a single female (a 
small specimen, probably var. longicarpiis, obtained from the ''loggerhead sponge" at Abaco) was 
found to be infested with this singular parasite. We may therefore regard it as very rare under 
these conditions. 



MBMOIUS OF THE NATIONAL ACADEMY OF SCIENCES. 463 

The sections of these embryos were very kindly examined by Professors .loseph Leldy and W. 
G. Farlow. In reference to them Dr. Farlow writes as follows: 

The parasite is certainly of great interest. I eanuot tind any description of it iu botanical literature, although 
it appears to be a I'linjjns beloni;iug to Chytridiacea-. 

The fungus has no mycelium, but is composed of single cells of various sizes. In a section 
like that shown iu Fig. 199 nearly one hundred large cells or cysts can be counted, and it is seen 
that the jieripbeial parts of the embryo are packed with them. These embryos were alive, 
although the embryonic cells were considerably altered from their normal condition, where they 
came in contact witli the parasitic growths and showed traces of degeneration. 

The parasitic bodies are mainly (1) large naked cysts or encysted cells, and (:-') very small 
spore-like bodies. Tlie naked cyst {v. «., Fig. !!)!>) is a thick shell which has collapsed and curled 
up with the escape of its contents. It is yellowish and is unafiected by staining reagents. The 
surface of the cyst is covered with \ery uniform, short projections or tubercles, which refract the 
light in a cliaracteristic way. 

Other encysted cells contain a protoplasmic reticulum (c*'), and there an^ very similar but 
smaller bodies which are either naked or possess but a slight cuticuiar wall. These encysted 
bodies Just described i)0ssiblj' represent zoosporaugia, and give rise to the myriads of minute 
spores which occur in close relation with them. The spores (Fig. 199, ^7^, represented by small 
black (lots) are minute, oval, and highly retractive. In the eye and other organs certain nuclei 
take up the stain very eagerly and refuse to part with it. These are probably the nuclei of em- 
bryonic cells which have undergone modification. Occasionally one of the cysts appears black 
(c«^), which is due mostly, if not wholly, to refraction. 

According to Goebel, reproduction in the Chyfridiea' is effected by means of swarm spores. 
Resting cells occur, which germinate and become sporangia, producing large numbers of swarm 
spores. Some forms, like Chytridium, have no mycelium. Its single cells, which live on or within 
the host plant, after reaching their full size become zoosporaugia. These give rise to swarm 
spores, which are liberated into the water. The Chytridiece are described as parasites on other 
aquatic plants. Fungi, Alga', and Phanerogams. 

According to Dc liary resting spores are known to occur iu certain species. These develop 
directly into sporangia or i)roduce them after a short intermediate stage, and appear to resemble 
the sporangia iu size and in possessing a warty cellulose coat. 



APPENDIX III. 

Some early abstracts of this work (Alpheus : A Study in the Development of Crustacea) were 
included iu the Introduction published in the Johns Hopkins University Circulars, No. 97, April, 
1S92. The part relating to the enibryology of Alpheus was here printed in its unrevised form, 
and differs materially from the results of later studies which are given in this memoir. 

While this work was in press it was thought best to change the name Ali)heus minus of Saj- 
to the correct form, Alpheus minor. As some of the pages were stereotyped before this correction 
was made, both forms of the name appear. 

Adelbert College, 

Cleveland, Ohio. M;iy, 1892. 



464 MEMOIRS OF THE NATIONAL ACADEMY' OE SCIENCES. 



Plate T. 
AlphtuiK minor, drawn from life by W. K. Brooks. (Enlarged eight diameters.) 
Dorsiil view of a. si)eciineu of tbe gray variety of Gonodactylm chiraf/ra, twice natural size. 



Plate I. 




lVK.Bmo]<s,dU. 



HB w ii tjiip^i ^n^ *<r- Tt 



ALPHEUS M(NUS AND GONODACTYLUS CHfRAGRA. 



S. Mis. 94 30 



466 MEMOIRS OP THE NATIONAL ACADEMY OF SCIENCES. 



Plate II. 
Alpheus heferochelis, drawu from life by W. K. Brooks. (Four times life-size.) 



PLale II 




IV K. Brooks, del. 



fc*»»iM> ■■l<WipM>»>i O i m~ r* 



ALPHEUS HETEROCHELIS. 



468 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate III. 
Oonodactyhm chiragra, drawn by W. K. Brooks. 
Adult female of the greeu variety, in her burrow, with eggs, twice natural size. 



lleiiuiii's Naliouiil Ai ailfiuy of Scieures. 1889. 



Plate III. 




A 



ir. K.Jirooks, del. 



GONODACTYLUS CHIRAGRA. 



I 



I 
I 



470 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate IV. 
Adult male aBd temcile of Alpheus saulcyi, viir. brevicarpus, from Nassau, New Providence. 

Fig. 1. Lateral view of female from green sponge. x3J. 

Fig. 2. Dorsal view of the same. x3J. Parts only of tbe ovaries are visible in Fig. 2, while the 
eggs, which greatly distend the abdomen laterally, show plainly between the bases of 
the swimmerets. In Fig. 1 the small chela is bent downward, the position in which 
it is usually carried. In Fig. 2 the chelie are represented in the attitude of defense. 
The dactyle of the left " hand," or large chela, is raised preparatory to striking. 

Fig. 3. Small male. L = If i"- X 7i. Drawn under slight pressure, owing to which the antennal 
spines and the antennular exopodites have assumed an unnatural position. The pos- 
terior margin of the carapace is more correctly represented in Fig. 1. 



Plate /^: 




f|P^-^N^N' 



F. H. Harrirk, del . 



ALPHEUS SAULCYI.VAR BREVICARPUS. 



*— *— ii^rmniwiin- *tmy. 



472} MEMOIRB OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate V. 

Dorsal view of the adult male Stenopus hispirhis. Nassau, N. P., June, 1887. L = IJ in. L. first 
antenna, exopodite— 3J in., endopodite— 3| in. L. second antenna = 4|i in. xlf. 

Excepting the brilliant pigment bands the body and appendages are nearly white»and could be 
better represented against a black background. The arching flagelia of the antennae 
are greatly foreshortened, and the spines and setse are of necessity unduly empha- 
sized in a pen and ink drawing. 




CO 

Q 

E 

(0 



a 
o 

z 

I- 



:i 



a: 



474 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate VI. 

Fig. I . Part of section of egg, showing the male pronncleus. The female pronucleus lies nearer 
the center of the egg, is less regular in outline and has less perinuclear protoplasm. 
A single polar body (not represented) is seen in this section. It lies close to the sur- 
face of the egg, beneath the membranes, not far from the male pronucleus. It appears 
as a small mass of chromatin, which stains quite as intensely as the nuclei. Egg 
about 6 hours old. x 276. 

Fig. 2. Section of egg with four nuclei, none of which are at the surface, x 152. 

Fig. 3. Part of same section, showing the nucleus and surrounding protoplasm and yolk, x 276. 

Fig. 4. Lateral section, cutting yolk segment on a level with the disk-shaped nucleus. Compare 
Fig. 5 a. Eight-cell stage. Age about 12 hours. x276. 

Fig. 5. Section through egg in eight-cell stage. Compare Fig. G. Age about 15 hours, x 152. 

Fig. 6. Surface view of egg in the third segmentation or eight-cell stage. The egg membranes 
have been removed. The nuclei lie at a deeper level than they appear in the draw- 
ing. Compare Fig. 5. x 78. 

Pig. 7. Section of egg iu the fourth segmentation stage. Sixteen cells, x 152. 

Fig. 8. Fifth segmentation stage. Age, 19 hours. Cells not yet at surface, x 152. 

ITiG. 9. Invagination stage. A solid ingrowth of blastodermic cells has taken place at Ig, where 
a slight pit is formed. The section cuts obliquely through the invaginate cells, x 152, 

REFERENCE LETTERS. 

a, perinuclear protoplasm. 

Ch, chitinous eijg envelopes (removed, except iu Fig. li). 

Ep, ectoblastic cell. 

Ig, shallow pit of invjigination. 

y.c, yolk spherule. 



Plal& VI. 



FiiZ 





Figs. 





Fig.6. 




Figs. 




F.H.Herrick.dtl. 



STENOPUS HISPIDUS. 



476 MEMOIRS OF TBE I^JATIONAL ACADEMY OF SCIENCES. 



Plate VII. 

FiGr. 10. Left secoud maxilla of larva at the point of liatching, before the tirst molt, x 276. Com- 
pare with Figs. 25 anil 21. 

Fict. 11. First swimming larva, after the first molt, .seen from below. Pigment cells, brown. 
L=,JjJ\, in. (measured from tip of rostrum to median notch of telson). Length of 
rostruDi = jfo in- X 70. 

Fig. 12. Right first maxilla of first larva, seen from the outer side. Setse rudimentary. Compare 
Figs. 19, 25. x276. 

Fig. 13. Telson of larva before first molt, seen from below. Compare Fig. 11. The setre are 
invaginated and covered with a loose cuticle. x276. 

Fig. 14. Right first maxilliped of larva on the point of hatching, seen from the outer side. Setfe 
invaginated. Compare Figs. 22, 25. x27G. 

Fig. 15. Labrum and right mandible of larva, seen from above. x276. 

Fig. 16. Right third maxilliped of larva on the point of hatching, seen from the outer side. Com- 
pare Fig. 25. x276. 

REFERENCE LETTERS. 

a, ontermoBt spine in telson of larva at the point of hatching. 
d, equivalent of a in first locomotory larva. 
Lh, labrum. 



puxte vn. 




F.H.Herr,>J(,j€/. 



STENOPUS HISPIDUS. 



478 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate VIII. 

Fig. 17. Second larva after second molt. 'L—-f^g in. x 70. 

Fig. 18. Left mandible, outer side, of second larva. x27C. 

Fig. 19. First maxilla of second larva, x 27G. 

Fig. 20. Telson of second larva, seen from below. x70. 

Fig. 21. Left second maxilla of second larva, seen from the outer side. x276. 

Fig. 22. Eight first maxilliped of second larva, seen from the outer side. x27G. 

REFERENCE LETTERS. 

g g, gastric gland. 
.... the dotted line iu Fig. 20 points to the outer spiue, the equivalent of d, Fig. 11. 



Pldli; Mil 




/■.//■//'■nir.'r,,M . 



STENOPUS HISPIDUS- 



480 MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. 



Plate IX. 

Advanced pelagic larva of Stenopits hifipidus, from Beaufort, North Carolina, drawn from life by 
W. K. Brooks. 



Plate IX. 




W.KBmoks.del. 



SKt«««]X>taiUtav«f*iaiI^J<wTM . 



STENOPUS 



S. Mis. 94 31 



482 MEMoms OF the national academy of sciences. 



Plate X. 
Dorsal view of a larva like the one showu in Plate IX, drawn from life by W. K. Brooks. 



PlcLfe X 




Fiiure24. 



WK.BnHjks.cUl. 



STENOPUS 



S«»««»J*i*«Uiit"*»4 !**-'* 



4b4 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XL 

Fig. 25. Embryo nearly ready to hatch, released from the egg membranes. x70. Some food 

yolk is still unabsorbed; swimming hairs very rudimentary; compare Fig. 11. 
Fig. 26. Eight first antenna of older larva, x 70. 
Fig. 27. Profile view of hinder end of abdomen of same larva. x28. 
Fig. 28. Second maxilla of same larva, x 276. 
Fig. 29. Mandible of same larva, x 276. 
Fig. 30. First maxilla of same larva. x276. 
Fig. 31. Portion of third maxilliped of same larva, x 70. 
Fig. 32. Terminal segment of second pereiopod of same larva, x 70. 
Fig. 33. First pereiopod of same larva. x70. 
Fig. 34. Portions of third, iourth, and rudimentary fifth pereiopods of same larva, x 70. 

REFERENCE LETTERS. 

A. I, first auteiina. 

A. II, second .antenna. 

Md., mandible. 

ilxpd. I, III, lirst anil third maxillipeds. 

R., rostrum. 

Til,., Th. 1, first maxilliped. 

Th. 3-Th. 5, third to fifth maxiUipeds. 

1, first maxilliped. 



Plale.XJ 



ty§.t5. 



H. 



Fi6.21 



RiM. 




F.H.Nerrock,cleZ-. 



FiiM. 



STENOPUS HISPIDUS. 



S4:t«aWiaKsaUMpa|lu4re NnrTtN 



486 MEM<JIB8 OF THE NATIONAL ACADEMY OP SCIENCES. 



Plate XII. 

Fig. 35. Older larva, taken in the tow-net outside of Nassau Harbor May 7, 1887. L=9""'". L. 
of eye- stalk =2°'™. L. between eyes=4.7'"". x 15. The long flagella of the antenn.t 
are conventionally represented to bring them into the plate. They trail above and 
behind the animal as it swims through the water. 



rUtte w. 




Figure 55. 



FH.Hem-rJf.-M. 



STENOPUS HISPIDUS. 



SM>«a»*MM L *^l » H hWwTa* 



488 MEMOIRS OF TBE NATIONAL ACADEMY OF SCIENCES. 



Plath XIII. 

Fig. 36. First maxilla, outer side. Adult male, x 15. 

Fig. 37. Lateral view of carapace of adult male. x5. 

Fig. 38. Left mandible, outer side. Adult male, x 14. 

Fig. 39. Stalk and portion of flagella .of left first antenna, seen from above. Adult male, x 5. 

Fig. 40. First right pleopod of male, outer side, x 14. 

Fig. 41. Left second antenna with flagellum cut ofl' near its base. Adult male. Seen from 

above, x 5. 
Fig. 43. Second maxilla of adult male, x 14. 

Fig. 43. Eight first maxilliped from outer side. Adult male, x 14. 
Fig. 44. Eight second maxilliped, from outer side. Adult male, x 14. 
Fig. 45. Eight third maxilliped, from under side. Adult male. x5. 
Fig. 46. Eight first pereiopod, under side. Adult male. x5. 
Fig. 47. Eight fifth pereiopod, under side. Adult male. x5. 



PlcUe, XIIl. 



Fi^M. 



Fi$.S8. 



Fi6.59. 




Fi^.44. 



FH Heiri^k.del. 



STENOPUS HISPIDUS. 



SwtBb«JtaMUrfCnfha(tb|i»TM 



490 MEMOIRS OP THE NATIONAL ACADEMY OF SCIENCES. 



Plate XIV. 



Metamorphosis of Gonodactylus chiragra, drawn from life by W. K. Brooks. 

Fig. 1. Dorsal view of egg just befere hatching. 

Fig. 2. Front view of the same egg. 

Fig. 3. Side view of the larva immediately after hatching. 

Fig. 4. Side view of the same larva after the first molt. 

Fig. 5. Side view of the same larva after tlie second molt. 

Fig. 6. Dorsal view of the larva at the beginning of its pelagic life. 



PLate XIV. 




I\ K.llmnbs.iJ-J. 



GONODACTYLUS CHIRAGRA. 



.>»!»=■•. wif|lM|<fc* 'a* 



492 MEMOmS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XV. 

Metamorphosis of Oo^wdactylus chiragra, drawn from life by W. K. Brooks. 

Fig. 7. Dorsal view of the larva shown in PI. xiv, Fig. 3. 

Fig. 8. Ventral view of the same larva. 

Fig. 9. Dorsal view of the larva shown in PL xtv, Fig. 4. 

Fig. 10. Ventral view of the larva shown in PI. xiv, Fig. 5. 

Fig. 11. An older larva in dorsal view. 

Fig. 12. Same in ventral view. 

Fig. 13, Raptorial claw of a still older larva. 



PliUe XV. 




W.K.Btt>oks,deJ.. 



GONODACTYLUS CHIRAGRA. 



Utwa Wii^T, I atwiniMi 'j^tmi Ta> . 



494 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENOES. 



Plate XVI. 

Metamorphosis of Alpheus, drawn by W. K. Brooks and F. H. Herrick. 

Fig. 1. Third larval stage of Alpheus minor from below, drawn by W. K. Brooks. 

Fig. 2. Second larval stage of Alpheus minor, about one- tenth of an inch long, drawn from below 

by W. K. Brooks. 
Fig. 3. Telson of the Nassau form of Alpheus heterochelis during the second larval stage, drawn 

at 10 a. m., April 17, 1887, by F. H. Herrick. 
Fig. 4. Second antenna of Alpheus minor during the first larval stage, from the inside drawn by 

W. K. Brooks, May 13, 1881, D. 2. (Zeiss lenses.) 
Fig. 5. First and second maxillae of the Nassau form of Alpheus heterochelis during the fourth 

larval stage, drawn by W. K. Brooks from a sketch by F. H. Herrick. The larva at 

this stage is shown in PI. xii. Fig. 3. 
Fig. 6. First maxilla o{ Alpheus minor (iin'ntg the first larval stage, drawn at Beaufort, June 2, 

1881, by W. K. Brooks, I). 2. 
Fig. 7. Second maxilla of the same larva. 
Fig. 8. Mandible of the same larva. 



l>l((lc SVl 




li rooks, »<• hfprrirjr ,</<•/ 



ALPHEUS 



496 MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. 



Plate XVII. 
Metamorphosis of Alpheus, drawn from nature by W. K. Brooks. 

Fig. 1. Side view of Alpheus minor after the' second molt and in the third larval stage. Zeiss 

A. 2. This larva was about ninety-five one-thousandths of an inch long from the tip 

of the rostrum to the tip of the telson. 
Fig. 2. Dorsal view of Alpheus minor after the first molt and in the second larval stage. This 

specimen was hatched at 9 p. m., May 30, 1881, and the drawing was made at 9 a. 

m. on May 31. The specimen was eight one-hundredths of an inch long. 
Fig. 3. Dorsal -view of a young specimen of Alpheus heterochelis from Beaufort. The specimen 

was one-fifth of an inch long. It was reared from the egg in an aquarium in the 

laboratory, and it was fifteen days old when the drawing was made. It is a little 

older than those which are shown in PI. xx, Figs. 2 and 3. 



PlcLie XVII. 




W.KRmoks.dU. 



ALPHEUS 



s*>*awhiiiiiiiip,n |[m»r«ti 



S. Mis, 94- 



-32 



498 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XVIII. 
Metamorphosis of Alpheus, drawn by W. K. Brooks from sketches by F. H. Herrick. 

Fig. 1. Side view of tirsl or second larval stage of Alpheus heteroehelis from Nassau, drawn on 
the night of April 15, 1887. Zeiss A. camera. / 

Fig. 2. Ventral view of the third larval stage of Alpheus heteroehelis from Nassau, drawn April 
IS, 1887. 

Fig. .3. Ventral view of fourth larval stage of Alpheus heteroehelis from Nassau, drawn April 
21, 1887. 

Fig. 4. First niaxilliped of the first larval stage of Alpheus minor. 



PUiLe XVIII 




Fii.2. 



Brooks, Ji- HerrUk ,clrt . 



ALPHEUS 



500 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XIX. 

Metamorphosix of Alpheus heterochelis at Beaufort, North Carolina, drawn from nature by W. K. 

Brooks. 

Fig. 1. Ventral view of the larva immediately after hatching. 

Fig. 2. Side view of the same larva. 

Fig. 3. Dorsal view of the antennule of the same larva. 

Fig. 4. Ventral view of the antenna of the same larva. 

Fig. 5. Mandible of the same larva. 

Fig. 6. First maxilla of the same larva. 

Fig. 7. Second maxilla of the same larva. 



PlcUe XIX. 




WK. Uroohs,dU. 



•inCadalJtMinfKH'^'^^"* 



ALPHEUS 



502 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XX. 

Metamorphosis of Alphcus heierocheUs from Beaufort, North Carolina, drawn from nature by W. K. 

Brooks. 

Fig. 1. Embryo just before hatching. 

Fig. 2. View of a larva which was captured in the tow net at Old Topsail Inlet, North Carolina, 
June 25, 1883. It is about eighteen one-hundredths of an inch long, and is a little 
younger than the one shown in PI. xvii. Fig. 3, and a little older than that shown in 
Fig. 3 of this plate. 

Fig. 3. Ventral view of a larva little younger than Fig. 2. 

Fig. 4. Telson and swimming appendages of the larva shown in Fig. 3. 

Fig. 5 First maxilla of the same larva. 

Fig. (i. Second maxilla of the same larva. 

Fig. 7. First maxilliped of the same larva. 

Fig. 8. Second maxilliiied of the same larva. 

Fig. 9. Third maxilliped of the same larva. 



Plata XX. 




W.K. Brooks, deJ.. 



ALPHEUS 



3«a«aWjMiBaLm|w^>ft|Cc fc-1ik 



504 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXI. 

Fig. 1. First larva of Alpheus saulcyi, var. breiHcarpus, from "loggerhead" sponge. Hatched at 

4 p. m., June 10, 1887. A small amount of unabsorbed food yolk remains in the 

stomach. x26. 
Fig. la. Line to indicate length of larva. L.=3.5°"". 
Fig. 2. Second larva of same, from brood hatched on evening of June 8. Food jolk nearly 

absorbed. About tweuty-four hours old. x26. 
Fig. 2a. Line to show length of larva. L.=4""". 
Fig. 3. Head of young from same brood. Four days old. x52. 
Fig. 4. Right first pereioi)od of larva of A. saulcyi, var. brevicarpus, before the molt preparatory 

to stage shown in Pig. 1. Seen from inner side. x52. Swimming hairs of exopodites 

rudimentary. 
Fig. 5. Egg embryo of A. saulcyi, var. longicarjyus, nearly ready to hatch. The large chela of the 

left first pereiopod is conspicuous below the autenni*. x46. 
Fig. 5a. To show natural size of the same. Slightly too large. Dimensions: xooXySoiuch. 
Fig. 6. First and second maxilla of first larva (Fig. 1) before preparatory molt. The parts are 

glov^ed with the embryonic skin, which is usually cast off at the time of hatching. 

X227. 
Fig. 7. Left first pereiopod of same, seen from inner side. x52. 
Fig. 8. Third larva of Alpheus saulcyi, var. brevicarpus. From same brood as second larva. Fig. 

2. Not over twenty-eight hours old. Food yolk not wholly absorbed. x26. 
Fig. 9. Telson and rudimentary uropods, seen from below, x 52. 



PlaU' XXf 




t ■ //. Hfirn,rh , tleJ. . 



ALPHEUS SAULCYI 



■ ^uU>'pi|k:i ^ IbB IM 



506 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXII. 

Fig. 1. Left second pereiopod of first larva of A. saulcyi, var. brevicarpm, from inside. x64. 

Fig. 2. Left third pereiopod of same, from inside. x64. 

Fig. :i. First maxilla of first larva of A. xanlcyi from brown sponge. x25o. 

Fig. 4. Left second abdominal appendage of first, larva of Alpheus mulctji, var. hrevica/rims. x 64. 

Fig. 5. Left first abdominal appendage of the same, x (U. 

Fig. 6. Eostrum of the same, seen from above, x 64. 

Fig. 7. Eight second antenna of the same, seen from below. x64. 

Fig. 8. Eight first antenna of the same, seen from above. x<>4. 

Fig. 9. Second antenna of young of Alphetis saulcyi, var. brevicarpus, six and a half days old. x 64. 

Fig. 10. First antenna of the same. x64. 

Fig, 11. Head of male of Alpheus smtlcyi, var. lougicarpuH, from "loggerhead" sponge. Median 

spine of rostrum wanting. Drawn from life. L.=5.5""". x3I. 
Fig. 12. Mandible of first larva of A. saulcyi, vnr. hreriearpus. x25o. 

Pig. 13. Left second antenna of male of A. saulcyi, seen from belov.-. No. « of Table I, p. 385. x 33. 
Fig. 14. Left second antenna of female of ^. saulcyi. From No. 9 of Table I. x3S. 
Fig. 15. Small chela of larva of A. saulcyi, var. brericarims, shown in Fig. 17, at time of hatching. 

Compare this with the same appendage of the adult. x64. 
Fig. 16. First pereiopod (small chela) of young of A. saulcyi, var. brevicarpus. From^green sponge. 

Compare this with Fig. 3,^P1. xxiv. x 64. 
Fig. 17. Front of a larva of A. saulcyi, var. loiigicarpus, which was hatched April 25. Drawn 

under pressure ; eyes slightly distorted. Equivalent to the ordinary third larva Fiff 

8, PL XXI. x64. 
Fig. 18. Part of stalk of right first antenna of male of Alpheus saulcyi, seen from below, showing 

the aural sc;ile. The median eye is seen ou the right, between the basal segments of 

the antennules. From No. 8 of Table I. x 26. 



Plate XXII 







FH.Hpm^Jr.'M 



ALPHEUS SAULCYI. 



SM«)a «Am> Ur*puMB« (« lb« T«i 



508 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXIII. 

Fig. 1. Eight second pereiopod of male of Alphens sauleyi, var. hrevicarpus, seen from the outer 

side. X 33. 
Fig. 2. Terminal segments of right fifth i)ereiopod of the same. x33. 
Pig. 3. Left mandible of the same, seen from the outer side, x 64. 
Fig. 4. Left first antenna, and left compound eye of the same, seen from above. x33. 
Fig. 5. Left third maxilliped of the same, seen from outer side, x 33. 
Fig. 6. Right second maxilliped of the same, seen from the outer side, x 64. 
Fig. 7. Eight first maxilliped, seen from the outer side. x64. 
Fig. 8. Eight second antenna of the same, seen from above. x33. 



Plulc XXjII 



Vi%2. 




r.H.H'-rrirh,,hl . 



ALPHEUS SAULCYI. 



iAfi«ii''X^>J9al>*ruh-|Ci: ^ 



510 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXIV. 

Fig. 1. Rig:ht fifth pereiopod of male of Alpheus saulcyi, var. brevicarptis, seen from outer side. 

x33. 
Fi». 2. Small chela of male of ^4..s«M7e^«, var. tonjf»c«»-^H.s. From No. 9, Table I. x33. 
Fig. 3. Small chela of male of A. saulcyi, var. brericarptis. From No. 8, Table I. Compare with 

the typical form of the other variety, shown in Fig. 2. x33. 
Fig. 4. First pleopod of male of ^. saulci/i, from "loggerhead" sponge. x33. 
Fig. 5. Left first pleopod of female of A. saulcyi, from '-loggerhead" sponge. A single egg is seen, 

attached to three hairs of the protopodite. The hairs are coated with glne, and the 

gluey threads are twisted into a chord, which is continuous with a tbin sheet of this 

sul)stance (the membrane of attachment or secondary egg-memJbraue which envelopes 

the egg). Below is seen a single hair, from which an egg has broken loose. Drawn 

from an alcoholic specimen. x33. 
Fig. 6. Right second pleopod of larger female of A. saulcyi, showing a number of eggs attached, 

seen from behind, x 14. 
Fig. 7. First maxilla of A. saulcyi. Endopodite bent out of po.sition, to a point below the large 

coxopodite. x 64. 
Fig. 8. Large chela of female of A. saulcyi, from "loggerhead" sponge. Compare with the brevi- 

carpus shown in PI. iv. x 33, 
Pig. 9. Right second maxilla of A. saulcyi, seen from outer side. x64. 



Plate^ XXIV 



Fiil 



Fii.2. 




F.H.Hnrri^J<,,JeJ . 



ALPHEUS SAULCYI, 



n&W,IMML*ipt)A«|^ lb*T«b 



512 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENGES. 



Plate XXV. 

Fig. 1. Surface view of segmenting egg of Hippa talpoiden. Thirty-two yolk pyramids present. 
X38. 

Fig. 2. Embryo of Hippa talpoides, showing optic disks and thoracic-abdominal plate. x38. 

Fig. 3. The central part of a transverse section of the ovary of the lobster, Homarus americanus, 
to show the progressive development of ova ; from the same series as that repre- 
sented, with less enlargement, in Fig. 6. Ovary taken in January. x281. 

Fig. 4. Section of egg of Hippa talpoides in yolk segmentation. Sixty-four yolk pyramids pres- 
ent. X 70. 

Fig. 5. Part of segmenting egg of Alpheus minor, showing a single large nucleus and two smaller 
nuclei. Compare with Fig. 23. x281. 

Fig. 6. Central portion of transverse section of ovary of the lobster, coiresponding nearly to that 
shown in Fig. H, showing the germogenal areas and the irregularly radiating blood 
sinuses. The diameter of the entire ovary is about twice that of the part represented. 
The largest peripheral ova have an average diameter of about one thirty-third of an 
inch, and their contents is only about one-eighth that of the ripe egg. x 70. 

Fig. 7. Egg-nauplius embryo of Hippa talpoides. Appendages appear as simple buds. x38. 

Fig. 8. Post-nauplius stage of Hippa. Abdomen bilobed at tip. Buds of at least three pairs of 
postmaudibular appendages. Figs. 1, 2, 7, and 8 are made from pen-and-ink sketches, 
and show only the general appearance of the embryo and its relation to the yolk. 

REFERENCE LETTERS. 

Ah. I'., thoracic abdomiual plate. 

B. C, blood cell. 

lil. S., blood sinus. 

Ch., chitinons eggshell. 

Ch. jr., limiting membrane of blood sinus. 

Ct. S., ovarian stroma. 

E. /., egg follicle. 

F. C, egg follicle. 
Ger., germogenal area. 

/. E., ovarian stroma (undifferentiated). 

0, o^—Qi', nuclei of ovarian stroma and developing eggs. 

0. D., optic disk. 

0. L., optic lobe. 

T. P., yolk pyramid. 

T. S., yolk spherule. 

Vac., yolk vacuole. 



PlcueXXV. 



Figl 




BIS. I (iSir ' 



jbP 










H 



I, ( I, s* 




^^ 






sS^ 



^ ,^^ur^ 



•::v^^_d 



\^x\ ,V -^:. ^ ^ ■3/''^^ •'''■ 



'\^Am\:v^':i'^^ 








Fi^.5. 



-YS. 



Yac. 



BIS. 



_-- ^. 



CA. 



F.^S. 



y 



<-ori; 



O.L. 



^ r-? 



B.C. oiF. fits. 



F.H.Herrick,del. 



SMtaiaWi t iiipijii n(^]h»Ta1i 



HIPPA, HOMARUS AND ALPHEUS. 



S. Mis. 94 33 



514 MEMOIRS OF THi: NATIONAL ACADEMY OF SCIENCES. 



Plate XXVI. 

Fig. 9. Sectiou tbiougb segiueutiug egg of Alpheus .saulcyi. Eigbt cells present. Yolk uuseg- 
mented. Egg membraues diagramatically represented, x 70. 

Fig. 10. Surface view of tbe same. Sixteen cells present. Yolk pyramids formed. Tbe peripb- 
eral nuclei are seen tbrough a thin layer of yolk, x 70. 

Fig. 11. Transverse section tbrougb the immature ovaries of Alpheus. Ovary taken in June, 
from female "in berry." Diameter of largest ovarian egg, one one hundred and 
sixty-eighth of an inch. Diameter of extruded egg, one liftieth of an inch. Contents 
of ovarian egg, oue thirty-seventh of that of tbe extruded egg. x-Sl. 

Fig. VI. Section through segmenting %gg of Alpheus minor, from Beaufort, North Carolina, show- 
ing nests of nuclei. x70. 

Fig. 13. Swarm or nest of nuclei, like those of preceding figure. x2Sl. 

Fig. 14. Sectiou through egg of Alpheus minor, cutting segmentation nucleus. Nucleus elongated, 
with irregular, indefinite boundary, x 70. 

REFERENCE LETTERS. 

Al. C, aliiuentary canal. 

B. C, blooil cell. 

B. S., blood space (possibly unnaturally distended). 

Ch., chitinotis egg envelopes. 

D. A., dorsal aorta. 

«, e', yonug ova. 

F. E., ovarian stroma. 

F. E.\ follicular epitheliuni. 

F. C, follicular epithelium. 
Ger., germogeu. 

Gfer.', position of germogeu iu ovary, with ova nearly ripe. 

G. F., germinal vesicle. 
0. W., ovariau wall. 

SS, swarm of nuclear bodies. 

Vac, yolk vacuole. 

Vit., vitellogen. 

X, cell shown in Fig. 30. 

Y. P., yolk pyramid. 



Haie XX17 



Fig.9. 



Fig. 10. 





Figll. 



B.C 




FigI2. 



FigM 





Fig.l4 




Vac. 



F.H.Herru-h.Jel.. 



ALPHEUS SAULCYI AND A. MINUS. 



516 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Platk XXVII. 

Fig. 15. Section of egg ofBabamau variety of Alpheux heterocheUs in typical yolk pyramid stage 
Sixty- four cells present, x 70. 

Fig. 16. Segmentation nucleus of egg of A. saulcyi, nearly central in jiositiou. x277. 

Fig. 17. Section of an egs of A; saulcyi, which was normally laid but unfertilized, .showing the 
female pronucleus. x70. 

Fig. 18. Degenerating nuclei containing spore-like bodies, from the egg-nauplius embryo, the 
structure of which is shown in Pis. xli-xliii. x610. 

Fig. 19. Blood cells of adult Alpheus. x 610. 

Fig. 20. Endodermal cells from the ventral wall of the primitive alimentary cavity of Astamis 
fuviatiUs. After Keichenbach (54) Taf. viii, Fig. 67. This is taken from the egg- 
nauplius stage to show the origin of " secondary mesoderm." The elements here 
marked 7h', k are described as cells which have originated from the endoderm, aud 
completed their metamorphosis into ordinary mesoderm cells. These may be com- 
pared directly with b, Fuj. 18, and s, s^, Fig. 21, from the egg-nauplius of Alpheus 
saulcyi, and are rather to be regarded as nuclear bodies in the earlier stages of 
retrogressive metamorphosis. x256. 

Fig. 21. Part of transverse section through the foregut of the egg-nauplius oi Alpheus saulcyi, to 
show the degenerative cell products. x610. 

« 

REFERENCE LETTERS. 

A. T. S., altered food-yolk. 
Ch., chitioous egg membranes, 
ec, ectoblast. 

»., nuclear body, with vesicular chromatin mass. 
Ic, i', Ij m, m'-3, nuclear products in yolk. 
Mes., mesoblast. 

N., NJ, nuclei of eutoblastic cells. 
n., nucleolus of entoblascio cell (not clearly shown). 
01., oil drop. 

Bet., protoplasmic reticulum. 
S, 8, e^., degenerative products. 
Sep., cleavage plane. 
Std., foregut. 
Vac, yolk vacuole, 
r., yolk. 

¥. P., yolk pyramid. 
T. S., yolk sphere. 



Plate XXVII. 



ng.i5. 







'V 



Fig. 18. 



h.. 



■9 



S W ■ 



Tii.n. 




Fi^.m 



^^ 



t) 



m 






Fig.20. 
nu. m. 



h.. 






d 




J.YS. 



Fi^M 




Mes. 



F.H.Hern^U.iU/ . 



ALPHEUS AND ASTACUS. 



518 MEMOIRS OF THE InIATIONAL ACADEMY OF SCIENCES. 



Plate XXVIII. 

Fir. 22. Part of section of segmenting egg of Alpheus minor from Beaufort, North Carolina, show- 
ing nuclear body in clear area. x277. -Ji 

Fig. 23. Swollen, probably degenerating, elements, from segmenting egg of ^-1. minor. x277. "^ 

Fig. 24. Section through base of yolk pyramid of c^g of PaUemonetes vulgaris. About sixty-four 
cells preseut. x 277. 

Figs. 25, 2(). Two successive sections through clear area in segmenting egg of Alpheus minor, 
showing degenerative products and nuclear bodies in process of breaking uj). x277. 

Fig. 27. Part of section through segmenting egg of Pontnnia dome.itica, before cleavage of the 
yolk. The egg contains three nuclei, one of which is seen to be in karyokinesis. 
'x277. 

Fig. 28. Part of section of an Alpheus egg in same stage as that shown in Fig. 9. Cell dividing 
indirectly and in horizontal plane. x277. 

Fig. 29. Section ofegg of ^Zp'*^*** *"**^'"'? pr^b^^^y ***''**'*''* •'***'^S"iP"tation. x277. 

Fig. 30. Enlarged view of cell .r. and part of section shown in Fig, 9. x277. 

REFERENCE LETTERS. 

Ch., egg nieniliraues. 

N., nucleus. 

P. A., protoplasmic area. 

r. N., periuuclear protoplasm. 

SC, (SC'-J, degenerating cell products. 

T, yolk. ~ 

T. B., .volk ball. 

y. S., yolk sphere. 

Vac, vacuole. 



Plate XXJIJI. 




Fig.22. 



Fi^.SS. 



%?^. 



mm 




Fi^.25. 



Rji: 




ri^.29. 



Fig. 50. 





J^JJ 



X(Fi^.9.) 



/^ //■ /ferrcc/c, del^ . 



SactiftWiiM^'ftipHi^a INvTok 



ALPHEUS AND PONTONIA. 



520 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXIX. 

Fig. 31. Part of section of egg of Bahaman variety of Alphetis heterochelis, showing two yolk 
pyramids. Same stage as Fig. 15. Sixty-four cells present, x '-iTi. 

Fig. 32. Part of transverse section of egg-nauplius of A. saulcyi, showing the fold of one of the 
antennsE and the mesoblastic cells and degenerative products contained within it. 
x610. 

Fig. 33. Wandering cells in yolk above the same embryo, showing protoplasmic union. xClO. 

Fig. 34. Part of section of egg of the Bahaman heterochelis in egg-nauplius stage, showing wander- 
ing cells, which have left the yolk and have attached themselves to the superficial 
ectoblast. The nuclei are flattened against the surface, but are clearly distinguished 
from the epiblast. x 610. 

Pig. 35. Part of transverse section of older embryo, showing blood cells and wandering mesoblast 
cell (Jlies.). Eye-pigment beginning to form. xClO. 

Fig. 36. Part of longitudinal section of embryo shown in Fig. 153, to show the degenerative prod- 
ucts of the dorsal plate, x 610. 

REFERENCE LETTERS. 

App., appendage. 
A.Y.S., altered yolk. 

B. C, blood corpuscle. 
Ch., egg membranes. 

C. P., united pseudopodia of two wandering cells. 
Ect., ectoblast. 

Ep., spindle-shaped nuclei of surface epiblast. 

Met., Mes.', mesoblast. 

Mu., muscle cells. 

Pn., cell protoplasm. 

PL, coagulated blood. 

s, s', degenerative cell products. 

.Sep., inner wall of yolk pyramid. 

S. W., outer wall of yolk pyramid. 

Y. C, wandering cells. 

Y. S., yolk sphere. 

Vac, vacuole. 



Platte XXIX 





Fig^^ Qr^^'v 



^ . ..--^XS. 



G^^OO 




Fi^.34. 




Ml 



1^.C. Fig.SS. Y.S. 

^ Q-- ..-Jtfes. 




Jpp. 



FigM. 



Ect. 




• ""•. 









-YS. 



A-- 






/■ '. H. Hforick, del, . 



\'tm II I ihi»-v-* 



ALPHEUS 



522 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXX. 

Fig. 37. Part of section of egg before iu pagination stage, showing primary yolk cells. All the 

figures on this plate, excepting Fig. 46, refer to the Bahainan form of Alphem hetero- 

chelift. X 277. 
Fig. 38-44. Consecntive sections of the same egg, showing the progress of the primary yolk cells 

in their migration from the blastoderm to the central parts of the egg. x 70. 
Fig. 45. Section through tlie same egg, .showing seinirtiagrammatically the structure of the yolk. 

X70. 
Fig. 4C. Section through the egg of .1. saitlci/i at a slightly later stage, but before invagination. 

The blastodermic cells lie at the surface, the primary yolk cells toward the center of 

the egg. Traces of the primary yolk cleavage are still seen at the surface, and a 

secondary cleavage has pccurred below the surface, x 7(1. 
Fig. 47. Surface view of the side of egg, corresponding to the germinal area iu nearly the same 

stage. X 70. 
Fig. 48. Tangential section, showing blastodermic cells of same egg. x 377. 

REFERENCE LETTERS. 

a, o'~', cells migratinfi; from blastoderui into the yolk. 

Bd. C, blastodermic cell. 

Ch., eggshell. 

G. D., embryonic area. 

Sep., yolk cleavage plane. 

F. B., yolk baU. 



fi^.37. 




PLaic AXV. 



Fi^5«. 



Fig39. 



rig.40. 



Fi^Al 






Fit42 




Fig.45 




Fi^.44 





Fig.46. 



Fig.41 



Fig 48. 





F.H.Hptrri^lf.JpJ . 



ALPHEUS 



524 MEMOIKS OF THE NATIONAL ACADEMY OF iSClENCES. 



Plate XXXI. 

Pigs. 49-55. Serial transverse sections througli the embryo in the invagination stage. In the 
most anterior section the germinal area (G. D.) is traversed, and in Fig. 53 the shal- 
low depression in the middle of the invaginate area is cut through. In Fig. 54 [Q. 
D.) we see the forward extension of the invaginate cells and the first trace of the 
thoracic-abdominal plate. The distinction between the primary yolk cells (Figs. 49, 
52, 53-55) and the invaginate wandering cells (b, 6", Figs. 52-54) and their i)roduct, 
which now begin their migrations, is very plainly shown. In Fig. 50, which cuts 
the shallow pit at the surface of the invaginate area, we see the amoeboid cells with 
large granular nuclei making their way from the bottom of the pit into the depths 
of the yolk. Figs. 49, 52-55, x 115. Figs. 50, 51, x 291. 

REFERENCE LETTERS. 

b, b'^ly', in-wandering cells derived from the invaginate cells and their products. 

Ch., egg capsule or .shell. 

Ep., ectoblaat. 

fi. Z)., embryonic area. 

/. C, invaginate cell. 

Ig., pit formed by the invagination. 

F. B., yolk ball. 

P. Y. C, primary yolk cell. 

F, S., yolk sphere. 



Plate XKXI. 



Fi^.49. 




Fig. 52. 




Ch. 



Fig. 50. . 



Y.S^ 



P $ 








li 



ej>. 



Fi^55. 




Fi^55.,. 



Ep. 



GJ>. 



\--YC. 



F.ff.//erric/{,(/e/. 



ALPHEUS 



SKiwft WJbitaiUtavqlUHC*llM TM 



526 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXXI I. 

Figs. 50, 59, 60. Longitiidiual serial sections through the entire euibryo iu the stage shown iu Fig. 
58. Fig. .59 is luediau. The primary yolk cells (P. Y. C, Fig. 60) can still be distin- 
guished from the wandering cells derived from the invagination {S. T. C, Fig. 60). 
In Fig. .59 a inimary yolk cell (P. Y. C.') is in the metakinetic stage of division. 
Traces of tlie iniinary segmentation of the yolk are still present, and the secondary 
yolk segmentation is very marked in the neighborhood of the wandering cells. 
Where the shell {(Jh.) is not removed it is seen to l)e considerably distended and to 
have epiblastic cells sticking to rt. showing the close adherence which normally exists 
between the egg ineml)ranes and the egg. xll5. 

Fig. 57. Section through egg, cutting germinal disk just before invagination. Twenty anil one- 
half hours older tiian yolk-pyramid stage seen in Fig. 15. x73. 

Fig. .58. Surface view of embryo after the uppearauce of the thorMcic-alidominal plate and the o])tic 
disks. The shallow depression which marked the invaginate area has disappeared. 
Its approximate position is indicated by Ig. Compare Ig., Fig. 59. x291. 

EEFKRENCE LETTERS. 

Ab. P., ventral plate. 

Ch., eggshell. 

Ep., Ep.', ectoderm. 

(t. T>., germinal disk. 

Ig., pit of invagination. 

L. Cd., lateral ventral bands. , 

0. D., optic disK. 

P. M., wandering cells, seen below surface, coiiiiii}; ofl' from ventral plate. 

P. T. C, P. T. C.\ primary yolk cells. 

Sep., yolk cleavage plane. 

S. r. C, S. Y. C, -wandering cells derived from the luvaginate cells and their products. 

T. Cd., cell area uniting optic disks. 

Y. B., yolk ball. 

Y. C, primary yolk cell. 



PUite XXXH 



SY.C. 




\--Ep. 



-PY.C. 



h'HII-rn^k.iUt 



ALPHEUS 



528 MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. 



Plate XXXIII. 

Pigs. 61, 62, 68, 69. Transverse sections of embryo in stage shown in Pig. 58, PI. xxxii. Pig. 61 
cuts the thoracic-abdominal plate, and Pigs. 68 and 69 involve the optic disks. Pri- 
mary yolk cells (P. Y. C. Pig. 69) are still plainly distinguishable. xll5. 

Pig. 63. Portion of median longitudinal section of the same stage. The larger and clearer nuclei 
in the invaginate area represent the mother cells of both mesoderm and eudoderra. 
The yolk ball or secondary yolk segment is characteristic of this stage. x291. 

Pigs. 64-67. Consecutive transverse sections of left optic disk of same stage before any thicken- 
ing has occurred. The most anterior section is represented in Pig. 64. x291. 

REFERENCE LETTERS. 

Ab. P., veutral plate. 

Ch., eggshell. 

Ep., ectoderm. 
^^ Ig., invaginate cavity. 

^ L. Cd., lateral ventral cord. 

0. D., optic disk. 

P. y. C, primary yolk cells. 

Sep., yolk cleavage plane. 

S. V. ' ., iu-wanderiug cells derived from ventral plate. 

T. B., yolk ball. 



PUde KXXm 



Fii 61. 



jb.p 




Fii.68. 




\ 



t 



— I 

-4 



FYC. 



N 



Sep. 



y 



V 



KH.H<>rrirk,aeC. 




P.YCA" 



-Ch. 



^P. 



Fi^. 64. oj). 




Fi^.69. 



XCd. 



OR. 



Q.D. 




« • 



PY.C. ■ 



■-•/ 



L^v- 



X. 



Ep. 



'iififlVi'illiiiiMtrti^irhiUrn MMrToA 



ALPHEUS 



IS. Mis. 94 34 



530 MEMOIEF OF THE NATIONAL ACADEMY OF SCIENCES. 



Platk XXXIV. 
(Stage IV.) 

Figs. 70, 71, 73, 74. Longitudinal serial sections of the entire embryo in the stage shown in Fig. 
72. lu Fig. 73 the i)lane of section is nearly median. The primary yolk cells are 
now generally indistinguishable from the other wandering cells. Compare cut, Fig. 
11, which shows the distribution of the wandering cells at this stage. xll5. 

Fig. 72. Surface view of embryo in Stage iv. Rudiments of the mandibles and first pair of autennse 
are present. An area of cell ingrowth in the optic disks {C. M.) is characterized by 
the large size of the nuclei. From them and their j)roducts the optic ganglion takes 
its origin. Some of the surface cells on either side of the middle line were acciden- 
tally cut away. x291. 

KKFKBENCE LBTTEKS. 

-). (/. ), proliferating center of first .auteuna. 

Ab. P., ventral plate. 

C. M., proliferating area of optic disk. 

Ep., ectoderm. 

L. Cd., lateral ventral cord. 

Md., prolifer.ating center of mandible. 

O. D., optic disk. 

T. Cd., transverse cord uniting optic disks. 

T. B., yolk ball. 

F. C, Y. C, wandering cells. 



PUite XXXIV 



YC- 




F.H.HerrirJ<,rlpl 



ALPHEUS. 



532 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Platk^ XXXV. 
(Stage IV.) 

Fia. T.'). Median lougitudiiial section of the entire embryo. One of the wandering cells, which is 
approaching the surface of the egg opposite the thoracic abdominal plate, is in the 
process of division. xll5. 

Figs. 76-83. Consecutive serial transverse sections through the left optic disk of same, to illus- 
trate the earliest stages in the thickening of the disks. The most posterior section 
(Fig. 83) cuts the first pair of autennie. x291. 

Fig. 84. Transverse section through the middle of optic disks, x 115. 

Fig. 85. Transverse section through thoracic abdominal plate, showing the multiplication of sur- 
face cells, by whicli the plate is increased, and cells below the surface {Y. V.) which 
pass into the yolk. x291. 

REFERENCE LETTERS. 

A. (i ), first antenna. 

Ab. P., ventral jilate. 

Ch., eggshell. 

C. M., pioliferatiug area of optic disk. 

ec, ec.i"^ ectodermic cells of ventral plate (Fig. yS). ec, (Fig. 80) ectoderuiic cell of o|itic disk. 

Ep., ectoderm. 

0. 0., 0. Z>'., optic disks. 

Eet , protoplasmic reticulum. 

T. Cd., transverse cord. 

r. B., yolk ball. 

T. C, Y. C'^, wandering cells. 

Y. S., yolk sphere. 



Plate XCVr 




Fi^SO. 

(0D!Fig.S4) <^ 



^ 



CM. 



'^ 1 



J6 



ec. 



Flg.SJ. 0Q)- 




^ 



i5' 



ca 



& 



.<9 






Ep. 



Fi^.82. 



& 



Jiiit. 




Ep. 



^b.P 



tlg.75. 



re. 



,fM- 




T.Cd. 



\' 

\ 



Y.(. 



Y.C' 



Fi^.84. 



OD. 




Fi^.S5. «■'■' '■'•' 



ec 



Ret. 








L5^® 



1:5. 



j gMfer 'D 



>r. 



F.M.Hprru-J<,ri^/ 



ALPHEUS 



534 MKJMoiKa oi' 'HUE katiunal academy of sciences. 



PJ.ATK XXXVI. 

(Stage V.) 

Figs. 86, 87. Parts of longitudinal sectioi).s of embryo seven or eight hours older than that shown 
iu Fig. 72. The optic disk (0. D.) is cut in Fig. 86, and in Fig. 87 its inner part is 
involvlid, with the outer border of the thoracic abdominal phite. There is no sharp 
demarcation between the protoplasm and the yolk, as is indicated by the dotted lines 
under the embryonic layers, x 291. 

Figs. 88-89. Longitudinal serial sections through the entire embryo, somewhat younger than the 
last, and six hours older than that represented in Fig. 72. The optic disk is sectioned 
in Pig. 90 through its central proliferating area (C. J/.), and the rudiments of the 
three naupliar appendages appear in Fig. 89. xll5. 

Fhj. 91. Transverse section cutting optic disks of embryo about nineteen hours older than that of 
Fig. 72 and twelve hours older than that represented by Figs. 80, 87. Wandering 
cells (Y. C) have traveled to remote parts of the surface, and karyokiuetic figures 
(Y. C,^, Fig. 89) i)rove that they are in active division. xll5. 

REFERENCE LETTERS. 

A. (/), rudiment of first .antenna. 

A. (II), rudiment of second imtenna. 

Ab. P., ventral plate. * 

App., area of appendages. 

Ch., eggshell. 

C. M., proliferating area of optic disk. 

fc, migrating ectoblast cell. 

Ep., ectoderm. 

Md., rudiment of mandible. 

0. D., optic disk. 

S., product of degenerating chromatin. 

St. J., sternal area. 

T. Cd., trausverse cord. 

1". C, F. C.'-^ wandering cells. 

Y. S., yolk sphere. 



Piale XKXVI 



Fi^86. 



S. YC. 




'■App.. 



Fig.88. 




Fig 90. 



m:b 





r^i^^- CM 



T.CJ. 




Y.C 



F.H.Homrk.-M,. 



ALPHEUS 



536 MBMOiKS OF THE :national academy of sciences. 



Plate XXXVII. 
(Stages V-VI.) 

Fig. 92. Part of trausverse sectiou, showing the structure of the keel-shaped ventral plate, and 
indicatiug the origin of inesoblast from the surface of the latter. x29i. 

Fig. !•.;{. Surface view of embryo with buds of uaupliar appeuilages. The intermediate area (St. A.) 
is covered by a .single layer of ectoderm. The invagination of the mouth has not 
yet appeared. Some nuclei of cells which lie immediately below the surface, especially 
in the thoracic abdominal plate region, are represented. x291. 

Figs. 94-9.5. Transverse sections of embryo, belonging to the same series as Fig. 92, to illustrate 
the structure of the thickening optic disks. Degenerating nuclear products («.', .s-.^, 
Fig. 95) are present, and two cells are seen delaminating side by side in Fig. 95. 

REFERENCE LETTERS. 

A. (/), rmiiiiR-nt of first anteiiiui. 
A. (11), nidiuient of SRCOiul antenna. 

Ab. P,, ventral j>late. ^ 4P 

f. M., i>roliferating area of optio ganglion. 
Ect., ectoderm. 
, Md., rudiment ol mandible. 

Mes., wandering cells (mesoblast) attached to ectoderm. 
- O. G., rndiment of optio ganglion. 

0. D., optic disk. 

».', s.-, products of degenerating chromatin. 
St. A., sternal area. 

T. Cd., transverse cord uniting optic disks. 
T. C, w.andering cell ; I'. €.', w.andering cell degenerating. 



Plate XXXVir. 



JhF 



Fig.m 




Fig. 93. 



red. 



-a-- "^ c:^ 




F.H.H<'TH^J<,dfl 



ALPHEUS 



S«t«iS »art»U Umi(l > H t^l*»'"' 



538 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXXVIII. 

(Stage VI.) 

Figs. 9(5-97. Longitudinal sections through the embryo shown in. Fig. 9.3. The more lateral of the 
two, Fig. 96, cuts the middle of the optic disk, and shows the large cells of the prolif- 
erating area, one of which is caught in the act of dividing. Fig. 97 cuts the inner 
portion of the optic disk and the ventral plate on a level with the budding mandible 
(Md,). x295. 

Figs. 9.S-100. Longitudinal serial sections through an embryo six hours older, from the same 
batch of eggs. The mouth (Fig. 98, Std.) has already appeared. The mesoblast, 
formed chiefly from wandering cells, is well established on either side of the middle 
line of the body, and is well seen under the folds of the appendages (Fig. 100, Mes.) 
into which it extends. The mesoblast represented by the lower layers of the ventral 
plate is still being increased by the migration of cells from the surface of this plate, 
as is indicated by cell ec, which is interpreted as a superficial cell about to migrate 
(in Fig. 98). In Fig. 100 a cell at the surface of the oi)tic disk is in the act of delami- 
uating. Large numbers of degenerating cells and their products are now encountered 
(S.C.,s.). X29.5. 

REFERENCE LETTERS. 

A. (/), bud of tirst autenua. 

A. {II), bud of second antenna. 

Ab., Al. P., Ad. F., ventral plate. 

App., area of appendages. 

C. M., proliferating area of optic disk. 

fc, ec.', migrating and dividing cells at surface of ventral plate. 

Eel., Ep., ectoderm. 

.yd., rudiment of mandible. 

.Mes., mesoderm. 

0. C, optic ganglion. 

0. D., optic disk. 

«., s.'"^, products of degenerating chromatin. 

S. C, S. C.'~-, cells in various stages of degeneration. 

St. A., sternal area. 

Std., stomodaium. 

T. C(i. , Transverse sheet of ectoderm uniting optic disks. 

¥., Y. S., yolk spheres. 



PUUe xxxriu 



Fig. 96 



Fi^.98. 




F. H. Horrij-J< , lid . 



ALPHEUS 



540 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 

Plate XXXIX. 
(Stage VI.) 

Figs. 101-1j05. Serial longitudinal sections of early nauplius embryo, twelve and one-half hours 
older thai) that represented by Figs. 98-100, PI. xxxviii, and eighteen and oue-balf 
hours older than the stage represented in Fig. 93, PI. xxxvii. The thoracicoabdonii- 
nal fold or papilla is now forming, apparently by the ingrowth of the surface ectoblast 
(Fig. 104, Ab. C). Fig. 102 is exceptionally favorai)]e in showing the nn(lotil)ted 
delamination of two cells standing side by side at the surface of the optic disk (ec). 
The common radial division of the ectoderm of the thoracico-abdominal region 
and other parts is illustrated by the cell ec' of the same section. Fig. 105 cuts 
the straight tubular stomodaeum. x 295. 

Fiti. 106. Longi tudinal median section of embryo several hours older than the last. A deep, narrow, 
transverse furrow {Ab. G.) now abruptly separates the thoracico-abdominal papilla 
from the sternal area lying between it and the stomodieum. x291. 

Fig. 107. Transverse section through the optic disks, from same stage. Cell delamination in this 
region is again met with. x291. 

Fig. 108. Longitudinal lateral section through entire egg, showing the distribution of wandering 
cells, and the relations of the embryo to the ovum. The eggshell is unnaturally dis- 
tended. An inner molt-ed membrane is present, as is better shown in Fig. lOG and 
Fig. 104, Mb. 

In Fig. 108 a large cell is seen at the surface, and below this a large cell followed 
by a row of similar cells. The first two cells possibly represent a budding ectoblast 
and mesoblast, and the rows of cells at the surface and below it are possibly derived 
from them, x 115. 

REFERENCE LETTERS. 

A. (/), ')iiil of tirst auteuua. 

^. (i/), bud of second antenna. 

Ai., thoracico-abdominal papilla. 

Ah. C, transverse superficial furrow by which fold of the thoracico-abdominal )>roee88 is formed. 

A. y. S., products of degenerating chromatin. 

B. '/.., budding zone. 
CA., eggshell. 

C. M., proliferating area of optic disk. 

Ci. S., cells on ventral side of yolk next to optic disks, probably representing mesoblast derived from 

wandering cells. 
ec, ec.', dividing ectoblastic cells. 
Ect., Ep., ectoderm. 

M.. wandering cell at surface behind thoracico-abdominal fold (Fig. 108). 
Mh., embryonic molt. , 
Aid., rndiment of mandible. 
Mea., mesoblast. 
0. D., optic disk. 
0. G., optic ganglion. 
O. S. G., brain. 
Pd., proctodaMiin. 

S., S.'-"-, products (it degenerating chromatin. 
^S. C, degenerating cells. 
St. A., sternal aiea. 
Std., stomodwum. 
F., F. S., yolk. 



IHule XXX1K 



FlglOl. 



O.D. 



MI). 



jIIII. 



.4mj: 




, }id. 



jak 



■^.rs. j(ni 



Jtd 




Jib. — 



.Ves. SU. 



Jb.C. 



.--CtS. 




Fi^.l05. 



OS.G. 



Sttl.- 

StA- 



^b. 




CM miOl. OSG. 



Ch. 




Fi^.108. 




Y.C. 



F.ff./ferrir/r,cfel. 



ALPHEUS 



f.«i«« wjtog*faair»>'M|f" *• T«* 



542 MEMOIRS OF THE NATIONAL ACADEMY OP^ SCIENCES. 



Platk XL. 
(Stage VI.) 

Fig. 100. Sketch of egg-naupliuss. Auus uot .so clearly seen in surface view, as represented in 
this and the following figure. Mouth on a level with antennules. x 72. 

Fig. 110. Sketch of older embryo. Appendages all bending backwards and inwards toward 
middle line." xTii. 

Fig. 111. Egg-nauplius less developed than shown in Fig. 109, bnt from same batch of eggs. 
The position of the mouth, which is postantennal from the first, is now on the middle 
line between the antenniB and the ajitennnles. The probable position of the anus 
is indicated, but it could not be clearly seen. The bud which represents the endop- 
odite of the antenna is just appearing on the right side, x 157. 

Fig. 112. Oblique transverse section, through egg-nanplius of a common shore crab of Beaufort, 
North Carolina, jirobably Sesarma. x286. 

Fig. 113. Median longitudinal section, through a similar embryo. The egg membranes are not 
naturally shown. The yolk is diagramatically represented. Wandering cells occur 
in it (1'. C), and in Fig. 113 degenerative products {Deg.) are met with. x286. 

REFERENCE LETTERS. 

A., anus. 

A. (I), auteuiial bud. 
A. (I), antennnlar bvid. 
AJ>., thoracico-abdoraiaal fobl. 
Cli., eggshell. 

Dei/., degenerative cell jtroducts. 
Ep., ectoderm. 

GL, ectoblast ofnenral plate. 
H., mesobla.st cells, foriuiug rudimentary heart. 
Bg., hind gut. 
Lh., labruxu. 
Md., mandibular bud. 
jUes., mesoblast below Kurfacc. 
O. 0., optic ganglion. 
O, Lr., optic lobe. 

O. S. (i.-i S. O. G., rudiinentary brain. 
.S«rf., Btoinodasuni. 
Vac, vacuole. 
F. C, wandering cells. 
-yumbem 114-125 mark the plants of the. transverse and longitudinal sections represented on J'ls. 

XLI-XLIII. 



Plate XL 



Fi^.109. 



SOG. 



Ml). 
-Std. 




Fig.no. 



Fig.lll. 



O £? o 



o 
o 






op 




c^^ 



O^S^\ 






^^. .©=^0 I) 




Ep. 



O.G. 



J).L. 

soa. 

J,b. 

Std, 



Mtl. 



Mes. 

J[d 

Mc(l). 



Ab. 



Fii.115. 



Y 

Vac 


St±. 


Ep 


Lb. 
Deg. 




Hg 




r.H.Hprn.rJ<,d<U . 



ALPHEUS AND SESARMA? 



544 MEMOIKS OF THE NATIONAL AOADEMY OF SCIENCES. 



Plaik XLl. 

(SUij,'e VI.) 

Figs. 114-llS. Transverse serial sections of egg-miui)lius in staye shown in Ji'ij^. 109. Plane of 
sei^tion indicated in Fij?- HI, which is from an embryo a trifle less advanced. The 
lobular condition of the enlarged optic disks is well shown in Figs. 114, 115. In 
Fig. 114 a deUiminating cell («■.) at the surface of the optic lobe is cut, and in Fig. 
115 a superficial ectodermic cell next the brain is dividiug perpendicularly. The 
intimate fusion of the brain and the oi)tic ganglion is seen in Figs. 11.5, 116. Fig. 
117 cuts the stomodieum passing through the mouth and the antenna;. Mesoblast is 
already well established in the pockets of all the appendages, as indicated at an 
earlier period. DegenL'rating cell products (>S., A. Y. S., Fig. IS) are very abundant 
in the region of the ^tomodieum, and occur also in the appendages (>S.~S.\ 6'. C, Fig. 
118). x2!)l. 

REFERENCE LETTERS. 

A. (/), antenual Inul. 

A. (II), antennular bud. 

A. Y. S., alteration products of yolk. 

Ct. S., cells partially covering brain, derivativos from yolk-wanderm;; bcIIs. 

ec, surface cell of ectoderm dividing horizontally. 

Ect., Ep., ectoderm. 

3/(i., mandibular bud. 

Md. (r., mandibular ganglion. 

J/. -F., median furrow. 

O. G., optic ganglion. 

O. L., optic lobe. 

Ret., protoplasmic reticulum. 

.S. A'.i, products of cell degeneration. 

5. O. G., brain. 

Sid., stomodaium. 

¥ac , vacuole. 

F., r. C.,-yolk. 



Plate XL!. 



Fi§n4. 




cc. 



O.G 



O.L. 




O.L 



SOG. 



Y.S. 



Fig. 116 




MF. SOG. 




Mes. 



Rpt. 



Vac. 



Std 

A.r.s. 



s.c. 



Fig.ll8 








Jtd. 






Md.G. MF 



A.in). 



s.c. 



F.H.HerrUk,del. 



SKtata WdlNtaaMwqfa^CUlM Tot 



ALPHEUS SAULCYI. 



S. Mifi. n4 3o 



546 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XLII. 

(Stage VI.) 

Figs. 119-122. Serial transverse sections of the egg-nauplius, continued from PI. xli. In Fig, 
120 a transverse row of cells with large clear nuclei is seen. This is probably a 
series of budding ectoblasts and mesoblasts, already referred to. Wandering cells 
appear to be settling down upon all parts of the embryo. In the thoracico-abdomi- 
nal fold (Fig. 122, tom.) the abdominal muscles are already nndergoing differentiation 
out of the mesoblast of the ventral plate. x295. 

REFERENCE LETTERS. 

A., ;in.al invaginalion. 
J. {II), antennal bud. 
Ab., alKlomeu. 

A. T. S., yolk umlergoing change. 
B.Z., budding zone. 
\ lict., ectoderm. 

/TV/., intestine. 
Aid., ni.andible. 
Mil. (1., mandibular ganglion. 
Mcs., nii'sodcrui. 
M. F., median gmovn. 
Mu., muscle cells. 
Mx. (1), first maxillary bud. 
8.', products of cell degeneration. 
<S. C, degenerating cells. 
Y., yolk. 

T. C, T. C, wandering cells. 
Vae., vacuole. 



MxiU XUI 



JYS. 




o 



Vac 



O 



0D« ^o (X^^c,....^^^^ 



Fig.l2l. 




YC. 



F. Jl H<'rnj-]< ,,U/ . 



ALPHEUS SAULCYI. 



s«iMawifciiMirtip^w«euit»Tgt . 



548 MEMOIRS OF THE :NAT10NAL ACADEMY OF SCIENCES. 



PJ.ATE XLIII. 

(Stage VI.) 

Figs. 123, 124. Completion of series of transverse sections of oggnaiiplius. Cells marked jMes. 

probably represent eui]o<lerm in Fig. 121. The heart is being formed at abont this 

time out of mesoblast eells at 7/, Fig. XLiii, and the en<loderm forms a jdale between 

it and the central yolk (v, I'Mg. 133). x295. 
Fig. 125. Median longitudinal section of same stage. Compare with Fig. 106. The thoracico- 

abdominal fold is now distinctly directed forward, an i is overgrowing the sternal 

area between it and the mouth. The stomodaium is a bent tube. x295. 
Fig. 126. Transverse section, cutting proctodteum. From an embryo of about the same age as 

that represented in Fig. 106. x29.5. 
Fig. 127. Transverse section of embryo and entire egg oa level with anus, showing wandering 

cells (T. C, r. C.'-'). x7i. _ 

REFERENCE LETTERS. 

J., auiil iuvaginatioii. 

Ab., abdomen. 

A. Y. S., altered food yolk. 

CVi., eggshell. ^ 

Set., Ep., ectoderm. 

Gl., ganglionic rudiment. 

H., rudiment of heart. 

Bg., intestine. 

Lb., labrum. 

Mb., embryonic molt. 

.!/««., mesoderm. 

Mo., month. 

Pd., region of proctod;eal invagination. 

«.,s'., products of cell degeneration. 

S. C, wandering cells, probably in early stages of degeneration. 

■S'. 0. G., rudiment of brain. 

St. A., sternal area. 

Std., stomoda-um. 

r., yolk. 

¥. C, Y. C.'--, wandering cells. 

Y. S., .yolk spherules. 

Vac, vacuole. 



PlaU' XUll 



Fii.m. 








Fig.m. 



>o 



,0, 



._y 



^ «^55^ rP^C, ^Q{ 



o 



'M3^ 






.;15CQJ,:^=^0%;^<J- 



Fi^.m. 



Vac: 



Pd. 




-Y 



.-.- YC. 



'C}v. 



F.H.H&TUJr,cl,J.. 



ALPHEUS SAULCYI 



550 MEMOIRS OF THE NATIONAL ACADEMY OP SCIENUES. 



Plate XLIV. 
(Stage YII.) 

Fig. 128. Transverse section through embryo, in the region of the first maxilla. Nervous system 
not yet diflferentiated from the skin. x234. 

Fig. 12!). Lateral longitudinal section through optic lobe and extremities of autenufe The differ- 
entiation between the retinal and ganglionic parts of the eve is very clear Meso- 
blastic cells, representing rudimentary muscles, are .seen attached to the body wall. 

Fig. 130. Surface view of embryo of this stage, wich buds of four post-mandibular appendages 
present The antenn* are covered with a hairy exuvium, which was probably 
stripped ofi- from the anteunules in this preparation. The mouth is concealed by the 
labrum, which nearly meets the thoracico-abdominal fold. The anus is situated 
nearly at the extremity of the latter, which is slightly emargiuated. x 137 
Fig. 131. Median longitudinal section in the series from which Fig. 129 was taken x '>34 
Figs. 132-135. Serial transverse sections through embryo in similar stage. The germinal 'layers 
dehnitely established in the egg-nauplius stage, are clearly differentiated at" this 
period. An incomplete layer of elongated ceil.s (probably mesoblastic in origin com- 
■ ug from wandering yolk cells), Mes., Figs. 131, 132, is seen between the yolk and 
the neural thickening, from which the nervous system is in process of <levelopmont 
In Fig. 134 rudimentary muscles suspend the stomoda^um to the body wall, and in 
Figs. 133 and 135 the three germinal layers can be clearly seen. The heart is repre- 
•sented by the space filled with mesoblast and sernm, between the entoblastic lamella 
and the ectoblast. x 234. 

BEFEKENCE LETTERS. 

A. I, first antenna. 

A. II, second antenna. 

Ah., thor.acico-abiloujinal fold. 

A. T.S., .alteration products of the yolk. 

Ed., ectoderm. 

End., endoderm. 

O. L., rudiment of optic ganglion. 

(H. A. II, antennular ganglion. 

Lb., labrnm. 

Mes., mesoderm. 

ifo., mouth. 

Mu., rudimentary muscles. 

Mx. I, first maxillary bud. 

O. E., retinal portion of optic lobe. 

S. O. G., brain. 

Sid., stomodfeuni. 



Pi((tc XLi\: 



Fig.m. 




End. 



Figm. 




G.l.JUl. 



f.H.HemcJ{,det. 



ALPHEUS 



552 MEMOIK8 OF THE NATIONAI, ACADEMY OF SCIENCES. 

Platk XLY. 
(Stage VIII.) 

Fig. 130. Lateral loagitudiual section of embryo in stage intermediate between YII and VIII, 
represented in surface view in Fig. 110. To this phase also belong Figs. 137, 144, 
and 14.5. Fig. 136 is to be com[)ared wiMi tlie sliglitly older embryo in Fig. 129. 
Blood cells {B. (J.) and other wandering ceils are liere seen settling down upon the 
body wall. A wandering cell is also seen nearly in contact wit li t lie optic ganglion, x 241. 

Fia. 137. Transverse section of embryo in same jdiase, just Iteliind tlie level of the first antennae, 
showing the relations of the wandering cells at this period to the embryo and egg. x 61. 

Figs. 138, 139. Serial longitudinal sections through embryo in Stage VIII. Fig. 138 should be 
compared with Figs. 136 and ll'!). All the ganglia of the nervous system, at least as 
far back as the eighteenth segment, are marked at the surface by deej) constric- 
tions. The ganglia of the nineteenth and twentieth segments are less distinct. The 
ganglia of the eleventh segment lie in the angle made by the thoracicoabdominal 
flexure. Wandering cells occur in the yolk, but are less abundant, and the products 
of cell degeneration, which enter into the general nutrition, have mostly disappeared. 
•X241. 

Figs. 140-14.'i. Parts of sections taken at various points on the surface of the egg (series to which 
Figs. 136, 137, 144, 145, belong), remote from the embryo, to show the role of certain 
wandering cells which reach the surface and represent mesoblast. In Fig. 140 two 
cells (MS., ws.') are partially flattened against the surface, but here, as in Fig. 142, 
the wandering cell ms. is clearly distinguishable from the spindle-shaped ectoderm 
cell on the left. Compare ¥\g. 34. x 241. 

Figs 144-145. Serial longitudinal sections through the embryo and entire egg to show the distri- 
bution of the wandering cells. Certain wandering cells not yet flush with the surface, 
enter into an organ — the dorsal plate {T)p.) — which is characteristic of a later stage 
(Fig. 153, Dp.). The strictly superficial cells of the dorsal plate are probablj' in all 
cases ectoblast, and some of the wandering cells degenerate before they reach the 
surface ectoblast. 

There seems to be a general dispersal of wandering cells from the vicinity of the 
thoracicoabdominal fold. The wandering cells which appear in this part were taken 
from four consecutive sections, including that represented in the drawing. xCl. 

REFERENCE LETTERS. 

^' 

A. I, lirst antenna. 

A. II, second antenna. 

an., lower margin of optic lobe. 

A. a. a., superior abdominal artery. 

li. C, blood corpuscle. 

b.m., basement membr.ane. 

cA., eggshell. 

Dp., dorsal plate. 

End., endoderm. 

O. IV-XniI, segmental ganglia. 

Gl., gangliogen. 

H., heart. 

hd., hypodermis. 

Hg., hindgut. 

mes., mesoblast. 

jiio., month. 

ms., ma.', wandering cells at surface. 

O. L., optic lobe. 

Rt., retinogeii. 

Std., stomodicum. 

Th. db., thoracic-abdominal fold. 

j/.c, wandering cells. 



Plate XLV. 




F. H. Mrrri^h ,,/p/ 



St<u¥iiaM»m ' i a^j»i^ a iiMr«t 



ALPHEUS 



554 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XLVI. 
(Stage IX.) 

Figs. 146-151. Serial trausverse sectious, through the embryo oi A. saukyi, at the time vrhen 
pigment is first deposited in the eye. In Fig. 146 the developmental history of the 
retinal layer is well shown. x230. 

Fig. loU. Nearly median longitudinal section of embryo in similar stage. x58. 

Pig. 153. Sagittal section of similar embryo, showing degenerating elements in yolk below «lorsal 
plate. X 58. 

REFERENCE LETTERS. 

J. I, first anteuna. 

A. II, second aatenna. 
Ab., abdomen. 

B. C, blood corpuscle. 
B. S., blood space. 
cp., carai)ace. 

Deg., degenerating cells. 

Dp., dorsal plate. 

End., eudoderm. 

/(/., foregut. 

fa., fiber mass of nervous system. 

g. II-III, brain. 

g.c, ganglion cell. 

g. VI. a. , anterior gastric muscle. 

H., heart. 

hd., hypodermis. 

Hi/., hindgut. 

Lb., labrum. 

Md., mandible. 

Mes., mesoblast. 

ilit.f., flexor muscle. 

ocm., oesophageal commissure. 

e.g., optic ganglion. 

O. L., optic lobe. 

pi., punct substanz. 

pr., perineurium. 

lit., retinogen. 

S. 0. 6f., supra-o'sophageal ganglion. 

T., telsOD. 

Tc, transverse commissure. 

Th., thorax. 

Vac, vacuole. 

y., yolk. 

y. C, wandering cells. 



Plate XIM. 



146. "A 




ALPHEUS 



556 MEMoms OF the national academy of sciences. 



Plate XLVII. 

(Stage IX.) 

Figs. 154, 155. Transverse sections tbrougii eutire embrjo of Alpheus saulcyi. In Fig. 154 a yolk 
nest is cut. Blood spaces occur near the surface of the egg. xtil. 

Fm. 15C. Cell nest, containing degeneration products. Its position in the yolk is shown in Fig. 
154. x245. 

Fig. 157. Part of median longitudinal section through the thoracic-abdominal flexure. The grow- 
ing endodernial epithelium and its fusion with the lining of the intestine are particu- 
larly well shown. Wandering cells appear to be uniting with the endoderm. x245. 

Fig. 158. Sketch of egg embryo, Alpheus saulcyi, of same phase as that represented by Fig. 157. 
X61. 

Fig. 159. Horizontal section through brain and eyestalks of a slightly older embryo. x<»l. 

Fig. 160. Part of transverse section of similar embryo on level with the mandibles. x245. 

Fig. Ifil. Superficial part of section of egg, showing surface cells, blood corpuscles, and a wander- 
ing cell on the edge of the blood space. x245. 

REFERENCE LETTERS. 

A. I, tirat auteuua. 

A. II, Becoud auteuoa. 
Ab., alxlomen. 

aor., aorta. 

u.y. S., grauulated yi>lk j)riHliicts. 

B. C, blood cell. 
B. S., l)lood spaci'. 
CVi., ejigsliell. 
c/*., carapace. 

Deg., products <it cell il< -generation. 
Ac/., ectodcrni. 
End., cudoderm. 

fa., fiber-substance of nerve cord. 
G. IV, ganglion of mandible. 
gc, ganglion cell. 
<//., fiber ball of second auteuua. 
U., heart. 
hd., hypodermis. 
hg., hiudgut. 

If., lateral liber-mass of brain. 
J/(t., inaudible. 
J/fs., mesoblast. 
Mil., muscle cells. 
Mu.f., flexor muscle. 
Uta., metastoma. 
n. c, neural cord. 
0. G., optic ganglia. 
I'/., optic enlargement. 
p. c, pillars of carapace. 
ji. r., perineurium. 
p. s., pericardial sinus. 
Rt., retinogen. 
Sid., stomod;»>uin. 
)>ac., vacuole. 
y.c, wandering cell. 
y. «., yolk nest. 



Plate XLVII 




mts. ^^. 

Jn^s /M muf 



F. N. Nerrick.cUC. 



ALPHEUS 



558 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Platk XLVIII. 

(Stage X.) 

Figs. 162-165. Parts of serial sections through the region of the heart and thoracic-abdominal 

fold to show the extension and relations of the endoderm. x57. 
Figs. 166—167. Parts of serial transverse sections of the embryo of Alpheus sanlcyi. x 125 
Fig. 168. Median longitudinal section through a slightly older embryo, showing the ventral 
endodermic fold (/). the foregnt still screened from the yolk, and the nervous 
system separated from the skin. x227. 

REFERENCE LETTERS. 

Ah , abdomeii. 

Ab. g. I, first abdomiual ganglion. 

aor., aorta. 

B. v., blood cell. 

B. S., blood space. 

cc, cryBtalline cone cells. 

Deg., products of degeneration. 

Sep., proximal retinular cells. 

Knd., endoderm. 

/., ventral endodermic fold. 

g. m. a., anterior gastric muscle. 

M., heart. 

Hg., hindgut. 

imb., intercepting membrane. 

mg., mesenteron. 

mo., mouth. 

mpgl, first maxillipedal ganglion. 

Mii.JE., extensor muscles. 

Mu.f., flexor muscles. 

0. G., optic ganglia. 

l>. -1., pericardial sinus. *■ 

A'*., retinogen. 

i?. O. (;., suprarOBSophageal ganglion. 

T., telson. 

Til., thorax. 

Th.g. I, ganglion of first ambulatory limb. 

y. c, wandering cells. 



u_ 



PI (id' XLVIII 







mo. 



Hg. ^OG 



F.H.H<frr,rltM'-l 



ALPHEUS 



MEMOIRS OF THE NATIOISIAL ACADEMY OF 



Platf, XLIX. 
(Stages X aiul XI [.) 

• 

Figs. 169-173. Parts of serial transverse sections through the embryo of Alpheus saulcyi in Stage 
X. Ill Fig. 173 the reproductive organ B. O. is cut. xlliO, (Fig. 173, x23'l.) 

Fig. 174. Horizontal section through nervous system of the tirst larva, on a level with the (Bso[)ha- 
geal comtnissiuos. x234. 

Figs. 175, 176. Transverse sections through the neural cord of the first larva. In Fig. 176 the 
transverse commissure of the ganglia of the tenth segment is cut and in Fig. 175 
the short longitudinal commissures between the tenth and eleventh segments are 
sectioned, x 129. 

REFERENCE LETTERS. 



.1. /, firstr antenu.a. 
J. //, second antenna. 
.tb., abdomen. 
ag., antennal glaud. 
B.C., blood oorpiiscleB. 
/>'. .S'., blood Hiiins. 
Hi:, braiiehia. 
cp., carapace. 
End., eiidoderm. 
/(/., forejrut. 
g. c, ganglion cell. 
Hd., liypodermiH. 
//(/., hiudgut. 

/./., lateral iibor-iiiaHx of. Iiraiu. 
Md., base of mandible. 
Mes., mesoderm. 
Mg., meseiiteron. 
Mil., mnscle. 

Mil. e., extensor muscles of abdomen. 
Mil./., flexor muscles of abdomen. 
.Mx., base of maxillic. . 
Mxpd., base of maxillipeds. 
II. c, neural cord. 
((/., optic fiber-mass of liiaiu. 
o.g., o))tic ganglion. 
Pi., perineurium. 
A". O., reproductive organ. 
eoy., brain. 

/. c. , transverse commissure. 
^. c, wandering cells. 



Plate XLIX 



J69. 



J75. 




muf jfrf mu.e. 

F.H.Herrick.dtl. 



ALPHEUS 



S. Mis. 04- 



-36 



562 MEMoiKs or the national academy of sciences. 



1'late L. 
(St:igo XL) 

Figs. 177-179, LSI, 182. Serial tiau.svi'rse vsectiiius of the eiiibijo of AJphaoi hefetoclwlis, which is 
ueaily reaily to hatch. The shell is soiuewhat diagraiiiaticailj lepresenteil audappeais 
thickened in Fig. I<S2, owing to a coagulable substance beneath It. The cells rep- 
resented in the .yoiU in Fig. 182 appear to be endodenii cells, which have become 
mechanically detached from the walls of the meseuteron. x74. 

Fig. 180. Nearly median longitiidiual section through a similar embryo. The eudodermal lining 
of the meiseuteron i.s not yet nearly completed, x 74. 

REFERENCE LETTERiS. 

Ab., VI, gauglioii ofnixtU :il)<luiiiiii:il appi'uilago. 

ag., nulenual gaugli»ii. 

ans., anus. 

ch.ex., external uhiasiiia. 

cct., ectoderu). 

end., endoderuj. 

/</., foregut. 

ijma., anterior gastric muscle. 

//., heart. 

7i(/., biudgut. 

hi/., Uyjiodcrniis. 

If., lateral fiber-niaiss of biaiii. 

OTjt. , meseuteron. 

mg.' ?/u/.^ of other lignres, pustcriii: lobe of midgut. 

»««./., liexor muscles of midgut . 

mil. «., extensor muscles of midgut. 

vein., (esophageal couiuiissure. 

o.pri., optic iieihincle. 

I{et., retiiiii. 

nog., brain. 

T., telson. 

1-4, ganglia of e.ve-stalk. 



Plate L. 



Fi^.m 




mue 



mue. 



F.H. Herri f]<,d>'J.. 



ALPHEUS HETEROCHELIS. 



564 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate LI. 

(Stage XL) 

Figs. 183-186. Continuation of series of transverse sections of embryo begun on Plate L. x 74. 

Fig. 187. Part of sagittal section of similar embryo, cutting eyestalk somewhat obliquely. The 
specimen was depigmented in nitric acid. The distal retinular cells, occupying the 
spaces (Pg. c.) between the peripheral ends of the cones, are not represented. x305. 

REFERENCE LETTERS. 

ac. J'., accessory pigment cells. 

nd. m., adductor of mandible. 

n. sa., superior abdominal arte'y. 

hg., branchiostegite. 

h. i\, blood vessel. 

0. . crystalline cone. 

eg., corneagen. 

cct., ectoderm. 

aid., endoderm. 

fg., foregut. 

B., heart. 

lit/., bypodermis. 

imb., intercepting mombrane. 

mg., midgut. ~ 

mg.^, posterior lobe of midgut. 

A/«., muscle of eyestalk. 

Mil. e., extensor muscles of abdomen. 

Mil./., llexor muscles of abdomen. 

o. c. m., oesophageal commissure. 

Pg. C, position of distal retinular cells. 

P.I., pericardial sinus, 

Ptii., proximal retinular cells. 

Ulit.', nuclei of proximal retinular cells. 

3, 4, ganglia of eyestalk. 



Plaie LI. 



Fi^.184. 



Fi^.m 



.ocm. 




■F.H.H^rrick.cU'J. 



ALPHEUS 



SK*<i>WiM»iIifcf«*^tC» M 



566 



MEMOIRS OF THE INATIO^'AL ACADEMY OF SCIENCES. 



Plate TJI. 

Figs. 1.S8, ]S0. Parts of trausverse serial sections tbrouffb tbe embryo of Pala'monefe.i rulga^-is, at 
the stage when pigment is just appearing in the eyes. In the anterior section (Fig. 
188) the retiuogen is a unicellular layer. x305. 

Figs. 100-191. Parts of serial trausverse sections through the brain, the optic ganglia, and eye of 
an embryo of Al2)heu.i heterochelifi. In the anterior section (Fig. 190) the clusters of 
cells which represent the ommatidia are well shown. Numerous ganglion cells are 
dividing. x305. 

Fig. 193. Part of transverse section through eye, optic ganglion, and brain at a later stage, x 305. 

RKFERBNCE LETTERS. 



A. }, first .antomia. 

.41)., abdomen. 

cc, cryst.alliiie cone cells. 

itnh., intercepting; menilirane. 

mes., mesoderm. 

Itet., retina. 

rtl.', rndimeutary eighth proxim.al retinnlar cell. 

sog., brain. 

T., telson. 

A'., stratum of large ganglion oells. 

1, li, 4, proxim.al, exteriKil middlr, .and distal segments of optic ganglion. 



Plate LII. 



Fii.m. 



Fi^. 189. 




Fi^.m. 







^frjr 



Fii.192 



F.HHerrUk,<le/. 



ALPHEUS AND PALAEMON ETES . 



568 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Pl.ATK LTTI. 

¥ni. 193. Part of trausverse sectiou tbrongh an embryo of Alpheus saulcyi, which is nearly ready 
to hatch, showing the third left branchia covered by the branchiostegite. x289. 

Fig. 194. Part of sagittal section of eyestalk of a .slightly younger embryo. x289. 

Fig. 195. Partof transverse .section, showing branchia, of the third larvaof ^l/;>/teH.s «(Htteyt( twenty- 
four hours old). x289. 

Fig. 190. Nearly median longitudinal .section of first larva of same. The anterior lobes of the 
midgut (}«(/') still contain unabsorbed yolk. Compare PI. xxi, Fig. 1. x58. 

Fig. 197. Part of transver.se section, showing the papilla, which bears the median eye in the tir.st 
larva of same, x 289. 

Fig. 198. Transverse section of first larva, cutting the lateral fiber balls of the brain, the anterior 
lobes of the midgut, and the green gland. x289. 

Fig. 199. Part of transverse section through an advanced embryo of yl/p/iews s«Mfcyi, parasitized 
by a fungus, most of the cells of which are encysted. From brown sponge, Abaco, 
Bahama Islands, v. Appendix II. xl86. 

REFERENCE LETTERS. 



all., abdomen. 

Ah. VI, sixth abilnmiual appcndajje. 

acp., accessory pigment cells. 

ag., green glaud. 

ag. «., end sac (?) of gl.and. 

««. «., superior abdominal .aorta. 

l>g., branchiostegite. 

!>. s., B. S., l)l(>i>d space. 

br.^, branchia of third left aiiibiilatnry limb. 

CO., crystalline cone cells. 

eg., corueagen. 

oh, lens. 

CO., crystalline cone. 

ca., f«.'--, cysts of parasite. 

cs.'', smaller, naked cells of parasite. 

(/.*■-'", segmental ganglia. 

!//., Kber-mass of second antenna-. 

gma., anterior gastric muscle. 

M., heart. 

Hd., hypodermis. 

Ilg., hindgut. 

Lt., labrum. 

I.e., longitudinal commissure. 

mg., midgut. 



mg.', anterior loltes of midgut. 

mg.', lateral lobes of midgut. 

mg.', posterior lobes of midgut. 

mo., mouth. 

ma., masticatory stomach. 

mu, e., extensor muscles of .abdonum. 

mu.f., flexor muscles of .abdomen. 

«. c, neural cord. 

oc, ocellus. 

oe., wsophagus. 

0. G., o.g., optic ganglion. 

of., optic enlargement of brain. 

op., ophthalmic artery. 

pa., i)ericardial sinus. 

pr., perineurium. 

S., rostrum. 

Set., retina. 

rtl., nucleus of proximal retimilar cell. 

sag., brain. 

S})., par.asitic growth. 

St. «., stern.al blood sinus. 

T.. telsou. 

y., yolk. 



]'l(iti: LIU 



I9:x . 








/,g. m^. °J" 






mu.e . 






^^W: -'#/ muf 






l.C 




P' Sis g' m^' i lb. 



//yr/ 



/■//J/rrnr/r.iM. 




BS.. 



B^ .'■;• "■ /^ 

mi- 



£•>«•> «BMaUi^<tfU('t « 



ALPHEUS 



570 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate LIV. 

FiOr. 200. Ommatidium of eyeof small adult Alpheus xaulcyi (from brown spongre) ; pigment removed 

by nitric acid. x2i)4. 
Figs. 201-20i. Transverse sections through four adjacent ominatidia of first larva of same. In Fig. 

201 the corneageu is cut, and in Fig. 2(»2 the nuclei of the cone mother cells. In Fig. 

204 the rhabdoni is sectioned and the seven jiroximal retinular cells. x294. 
Figs. 205-208. Transverse sections through adjacent ommatidia of the adult eye, taken at various 

levels. Fig. 205, the deepest secrtion, shows the peculiar seven-pronged tigure of the 

rhabdom. The proximal retinular cells a|>pear in sections, as if fused together, x 294. 
ViGH. 209-211. Transverse serial sections through the first larva of Alpheiis saulcyi. •x74. 

REFERENCE LETTERS. 

A. /, first aiiteuna. 
A. II, second antenna. 
a.C})., accessory pigment cell. 
ac.pii., nucleus of accessory pignient cell. 
ao., ear. 

Bin., intercepting or basement momhrane. 
CO., crystalline cone cells. 
eg., corneagen. 
cl., lens. 

Co., CO., crystalline cone. 
cmh., cone membrane. 
hd., hypodermis. 

me., membrane of distal retinular cells. 
nf., nerve fibers, 
oc, ocellus. 

og., optic ganglion. " 

of., optic enlargement of brain. 
pap., papilla of ocellus. 
p.g.c, distal retinular cells, 
/i'., rostrum. 
lib., rb., rbabdoin. 
Ket., retina. 
rtl., proximal retinular cells. 



noo. 



Plate Z/ir 




20/. 

me. 



W%. 



■^r'^^r^-fi'^ "^^^ 



^ 



m 



C.C. 




acpn 



207. 




205. 



.CO. 




..p4c 



204. 
CO, acp 

,-:rtl. 
■■rb. 
acp. 




206. 




cm 



Pi'^: 



Pi(^ Pi-c. 



208. 




m. 



net... 



209. 



■hd. 




2W. 



■n 



pap. 



,R. 





^^€0 



jii. 



ao 



M 



F.H.H<'rrir}<,ilK(. 



ALPHEUS 



572 MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate LV. 

(Stage XII.) 

Figs. 212-22.'?. Transverse serial sections of the first larva of Alpheus saulcyi from the same indi- 
vidual iis Figs. 209-211, excepting Figs. 222, 223. x 73. 

REFERENCE LETTERS. 

A. II, second anteuua. 

ad. m., adductor of mandible. 

ag., green gland. 

o/., antennular fiber-mass of brain. 

ao., ear. 

a.op., ophthalmic artery. 

Bg., brancUiostegite. 

B.gl., glaud-like body. 

B. S,, blood sinus. 
/;/., foregut. 

/«., liber-maes continued into ffisophageal commissure. 

gf., antennal fil)er-mass. 

(/«., lateral pouch of masticatory stom.ach. 

Li., labrum. 

//., lateral fiber-mass of brain. 

Md., mandible. 

Mg., midgut. 

Mg'., anterior lobe of midgut. 

Mg^., lateral lobe of midgut. 

Mp., septum between anterior lobes of midgut. 

M. S., masticatory stomach. 

MU., metastoma. ^ 

Mx. I, first maxilla. 

Mjrpd. I, first maxilliped. 

n.ag., antennal nerve. 

M. aw., autennular nerve. 

00., ocm., o\sophageal commissure. 

of., anterior tilier-mass and transverse commissure of brain. 

p.. F., pyloric valve of masticatory stomach. 

s(. «., sternal sinus. 



Plate LV 





B.S. 2/4. 



nop. 





219. 



220. 




ms. 



22 J. a op 




■ mxl. 



adjn. fnts. or 

F.H.HorrUJ<,clel. 



\mxpdl. 



222. 



msr 




ocm 



225. 

mp. ...flop 



st.s 




ms 



mxpd.I. 



FIRST LARVA OF ALPHEUS SAULCYI. 



574 MEMOIKS OF THE NATI02sAL ACADEMY OP SCIENCES. 

V 



Plate LVI. 

(Stage XII.) 

Figs. 234-235. Serial transverse sections through the first larva, continued from Plate L V. x 73. 

REFERENCE LETTERS. 

Ab. V, fifth abdominal appendage. 

a.i.a., inferior abdomiuiil aorta. 

a. op., ophthalmic artery. 

a. s. a., superior abdominal artery. 

hg,, branchio.stegite. 

ftr., branchia of ambulatory appendage. 

B. t>., blood sinns. 

gg. ' ^, middle, ventral, and dorsal lobules of posterior lobe of midgat. 

H., heart. 

hg., hiiidgut. 

hij., hypodermis. 

?c. th.-ab., longitudinal commissures uniting last thoracic with first abdominal ganglia. 

Mg., midgut. 

Mg. '', lateral lobe of nudgut. 

Mg. ^, posterior lobe of midgut. 

J/«., masticatory stomach. 

Mil. e., extensor muscles of abdouiou. 

Mii.f., flexor muscles of abdomen. 

Mxiid. I-III, lir.st to third maxillipeds. 

pleu., pleurou. 

pt., pericardial sinus. 

Th. I-V, first to tilth ambulatory limb. 




Plate LVI. 




ms. 



225. 



aop. 



.- "'^^ 



mxpd.I. 




: 'mxpdJI 



Sis- 




nixpdM. 




niu.f. 
^- mxpdm. 



228. ^^ 



^'•■J 



mu.e. 




229. 



miie ^ 



wuf. 




Th.l 



230. n. P^ 

/ hy. 



mu.e. 




mu.f. 



aia. 



Th.n. 



H 255. 



asa 



mue. 



mu.r 




ai a. 



25/ 



mu.e 




mu.f 



6r"' 



77i.I 



a\a 



a.sa 



254. 



mu.e. 




muf. 



..pleu. 



B.B. 



-Ic th-ab. 



aia 



BS. 25%. 



mu.e 



mu.r. 



bii^' W% 


i / 


M 


Thin. ^ 


> 

aia. 


*? 


mu.e 


255. 


.as.a. 



muf:: 



x3fei 




M.V 



Sum 9 W*rinL*^iiftai| a lb* Ta* 



FIRST LARVA OF ALPHE US SAULCYI. 



576 MEMOIRS OF THE :national acade.aiy of scie>-ces. 



Platk LVII. 

(Stage XII.) 

Figs. 236-245. Horizontal sections of lir.st larva, illustrating further the anatomy of the alimen- 
tary tract and the nervous system. x57. 

KEFERKNCE LETTERS. 

J. /, U, first auil second autenua. 

ag.. green gland. 

ttf., autennular tiber-niass. 

10., ear. 

hij., branohiostejfite. 

End., eudoderiii. 

/(/., foregut. 

/<)., liber-substance of tesophageal commissure. 

ijf.. liber-mass of second antennae. 

gg. '-', middle, ventral, and dorsal divisions of posterior lobe of midgut. 

kg., hindgnt. 

//., lateral tibermass of brain. 

Mil., mandible. 

Mg., midgut. 

ilg.\ lateral lobe of midgut. 

Mp., partition between anterior lobes of midgut. 

-)/(«., metastoma. 

Mjc.I, II, first and second maxillae. 

Mxpd. I-III, first to third maxillipeds. 

II. an., antennular nerve. 

li.c, ventral nerve-cord. 

of., anterior fiber-mass of brain. 

og., optic ganglion. 

lirt., retina. 

J^'l'- i-^, first to fifth aiul.nlalory limbs. 

y., yoik. 



Mate LVIl 




259. \i 




nc 




KH.Horrick,JeJ,. 



FIRST LARVA OF ALPHEUS SAULCYI. 






,^.»^VV* 



-la^Ar'^ - 



>^P*> 



f^iSi'^' 



'•^^A^^»^ 



m 



• jll^A^^ ^^0^Am,r ^^^ 






^^^r^r 



/*A ^ - 



A^^" 



rr;;v^ 



,^A^^ 



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*^'^i$'4' 



•-^k'-; -« , V 



't<>>^i«>^. 



>^ ~ N'T 



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^r"^^* 



ii;?w«£;' 



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I^^A 



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'^iks^ 






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^ -« > 



'k • > -. 









IH^ 



AH 



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^V <:'^:i*