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BROOKS, "PROFESSOR OF ANIMAL MORPHOLOGY IN THE JOHNS HOPKINS UNIVERSITY, 4 AND 1s i= HERRICK, _ PROFESSOR OF BIOLOGY IN ADELBERT COLLEGE, LATE FELLOW IN THE JOHNS» HOPKINS UNIVERSITY. fey é = “es Es iF rs . - va | WITH FIPTY-SEVEN PLATES. & ~ A a *. - . <= , ne P vs " . 2 3 he Ms ‘ i “> pave Sei N , “ ~ al Pe 7 La pie . ‘ 2° = ; : ra Beek a = vr . & ae: » ue Introduction. sure ‘Il. The life history of Stenopus hispidus. Section 1. Natural history of Stenopus. Section 2. Segmentation and the early stages. ~ Section 3. Metamorphosis of the larva. Section 4, The adult. — - Remarks. _ List of species. _ Literature of Stenopus. by Sig The habits and metamorphosis of Gonodactylus chi- ragra. Section 1. The structure and habits of the adult. Section 2. Metamorphosis. ~ . uly. The metamorphosis of Alpheus. _ p Section 1. The metamorphosis of Alpheus minos. Section 2. The metamorphosis of Alpheus hete- rochelis iu the Bahama Islands. _ Section 3. The metamorphosis of Alpheus hete- rochelis at Beaufort, North Carolina, Section 4. The metamorphosis of Alpheus hete- rochelis at Key West, Florida. _ Section 5. The larval development of Alpheus sauleyi. V. Alpheus: A study in the development of the Crus- : tacea. Introduction. _ Methods. ‘Parr First. Section 1. The habits and color variations of Alpheus. > . = \ - » be - ya , ata ae ¥: ie ™ ~ % hs ‘ - — p 4 oe ut ~- ‘~~ <> ae 7 ay HAS —w Ao ae 5 a er CONTENTS. Part First—Continued. Section 2. Variations i in Alpheus heterochelis. Section 3. The abbreviated development of Alpheus and its relation to the environment. ; Section 4. The adult. Section 5, Variations from the specific type. Section 6. Measurements. Section 7. The causes and significance of varia- tion in Alpheus sauleyi. Part SECOND. Development of Alpheus. Section 1. Structure of the larva of Alpheus sauleyi. Section 2. The origin of ovarian eggs in _— Homarus, and Palinurus, Section 3. Segmentation in Alpheus minos. Section 4. The embryology of Alpheus. Stages 1-13. Section 5. Notes on the segmentation of Crusta- cea. Section 6. Cell degeneration: Section 7. The origin and history of wenderas cells in 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). [With fifty-seven plates. ] 323 %, ‘ tse od ae ey ee YY ee ery 4 M ited thes * aa vy en ae ‘ rw. aah a7 * a ‘ 4 r : he 8 us a SL Oe re Oa eee a wis ath \ 5 hee nee Te ve . : : E CHAPTER LI. “rstacg, INTRODUCTION. / By W. K. Brooks. No great group of animals 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 peculiarities which serve to render the problem of their life history 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, by a continuous shell of excreted matter, and as 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 mollusk 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 arthropod 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 the old one, and as soon as this is thrown off the new one quickly becomes fully distended and solid. Asa 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 different in structare from the adults, and growth is accompanied by metamorphosis. As the changes of structure are. necessarily confined to the moulting periods, the stages of growth coincide with the stages of change in organization, and there is none of the indefiniteness which often characterizes the different larval stages of animals with a more continuous metamorphosis. On the contrary tlie nature of each change is as sharply 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 Crustavea, but another consideration, the fact that, with few exceptions, the higher Crustacea are marine, renders the problem of their life history nite more intelligible than that of any other class of animals. So far as the ontogenetic history of the metamorphosis of a larva is a recapitulation of ances- tral stages in 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 and their own living 5 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 adaptation 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 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. surround a modern terrestrial larva must, in nearly every case, be very different from those under which 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 the persistence of so many ancient marine types shows that the changes in the organic surroundings of marine animals take place much more slowly than corresponding changes on land. x 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 Claus has clearly proved 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, Claus’ 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 offered 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 présent time. Some of my results have been pub- lished in my monograph on Lucifer, in the Phil. Trans. Royal Soc. for 1882, and others are incor- porated in my report on the Stomatopoda collected by H. M. 8. 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 ‘‘ Alpheus, a study in the development of the Crustacea,” is entirely the work of Mr. Herrick; the one on the metamorphosis of Alpheus is based upon our combined studies, and that upon Stenopus 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. 3 > THE LIFE HISTORY OF STENOPUS HISPIDUS. During the six seasons which I spent at Beaufort, North Carolina, I captured in the tow-net, at different times, some six or seven specimens of a remarkable pelagic crustacean larva, all of them well-advanced and in nearly the same stage of development. 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- gestid, have retained the primitive or ancestral metamorphosis, and that its secondary modifica- tions are very slight as compared with those of ordinary macrouran larve, and also that the Beaufort larvee are new to science. (See Pls. rx and x.) These larve have the full number of adult somites and appendages, and in side view they are very suggestive of the Sergestidz. They are very much larger than ordinary pelagic larve 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 ~ te ene I. x we MEMOIRS OF THE NATIONAL AUADEMY OF SCIENCES. Byes middle line and are then swept backwards and outwards, describing at each stroke a circle equal in 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 June, 1886, our attention was at once attracted to a small, graceful, brilliantly colored prawn which was found in abundance among the coral. (See Pl. v.) It proved to be Stenopus hispidus, a species which is chiefly known to naturalists through specimens from the Indian and South Pacific oceans. It has been recorded as occurring in the tropical Atlantic, but our knowledge of the adult has been very scanty and imperfect, and nothing whatever has been known regarding its life history until Mr. Herrick 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 1s 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 principles, to find the least specialized species the most widely diffused; and one which holds its ground in so many parts 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 appearance, and also in its metamorphosis, Stenopus is one of the most highly specialized of the crustacea; and it owes its ability to survive in many seas to the accuracy and delicacy of its adjustment to. a narrow range of conditions, rather than to indefinite aud vague adaptation to many conditions. : Its antennz are unusually long and slender, and the acuteness of its senses, togéther with its very remarkable alertness; the quickness with which it perceives danger, and the rapidity with which it escapes; have tndoubtedly 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. P 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 dispersal and to the discovery of new homes. While we cannot state that the adult will not at some time be found upon the Atlantic coast of our Southern States, there is no evidence that this is the case, and the larvee 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 larve had therefore wandered more than six hundred miles from their birthplace. The species might therefore be diffused 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 ; Stenopus 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 protoplasm. This yolk is aggre- gated around a central nucleus, which divides, probably indirectly, into two, four, eight, sixteen 398 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 putlnes of the blasto- meres are sharply 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 bonus with individual peculiarities in which it differs from all of them. At the time of hatching (Pl. vi and Pl. x1, Fig. 25) it has sessile eyes, ibcomsaies antenne, an enormous mandible, a deeply forked telson, a long rostrum, and a complete series of append- ages as far as the first pereiopods, which are essentially like the third maxillipeds. 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 ordinar 'y macrouran (Pl. vit). 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 antennz are shortened like those of a zoea, and the maxillipeds Beceane the chief locomotor organs. As these larve could not be reared in captivity the later stages were studied from captive specimens, but Professor Herrick has proved that the Beaufort larve are either young Stenopi or else the larvee 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. X11). It isin the Mastigopus stage, with greatly elongated eyes, and with antennx 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 Sergestidie, the last two pairs of *‘ walking legs” are shed Atter 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 Sapp 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 corai 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 alge 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 porous coral limestone, or under the broken shells and fragments of limestone which lie upon ~ MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 329 - the buttom in shallow 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 hidden in the shelter which they find upon the reef. The most conspicuous characteristic of eh genus is the great enlargement of the claws of the first pair of walking legs. Both claws are large, but one of them is enormous, and it serves as a most formidable weapon of offense 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 pushed out to make a rapid thrust at any enemy. In nearly all the species the large claw terminates in hard, powerful forceps. The claw or dactyle is provided with a plug, which fits 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 mouth of the socket. As soon as the claw is released it is suddenly 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 Alpheus less than an inch long, hastened 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 attacks are harmless to man. The snapping propensity is exhibited both 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 claw, 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 stretghed 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 Alpheus heterochelis cut another completely 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 the 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 we 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 published 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 heterochelis. 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 aquaria in the laboratory, and the metamorphosis has been traced from actual moults. THE METAMORPHOSIS OF ALPHEUS. One of the most remarkable results of our study of the various 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 different species, the individuals of a single species sometimes differ more from each other, as regards their metamorphosis, than the individuals of two very distinet species. This phenomenon has been observed by us and carefully studied in two species—Alpheus hetero- chelis and Alpheus saulcyi—and 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 individuals 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 different from that of those which live on the coast of North Carolina, while those which we studied in the Bahama Islands present still another life history. In the case of the second species—Alpheus sauleyi—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 thau 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 aduits from North Carolina and those from the Bahama Islands, although their life histories exhibit a most surprising lack of agreement. In fact, the early stages in the lite of Alpheus hete- rochelis in the Bahama Islands differ much less from those of Alpheus minor or Alpheus normani than they 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 I received the American Naturalist with Packard’s very brief abstract of his observations at Key West upon the development of Alpheus heterochelis, and read with great surprise his statement that this speciés has no metamorphosis, since, while still inside the egg, it has all the essential characteristics of the adult. As I had under my microscope at Beaufort on the very day when I read his account a newly hatched 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 larve 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 larve 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 affinities and general resemblances, while their specific 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 1ts conditions of life chiefly aftects 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 larve are, a8 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 larve 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 be exhibited when the larve of one species of a genus have become adapted to a mode of life very different from that of the larvie of the other species of the genus. Thus those species of Aiginide whose larve are para- wae bal * | ia i hh co he Sea Beli aad: ¢ 7 ali a deh ¥ wets he ere *. x ‘ ey ~ , MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 331 sitic multiply asexually during the larval life and build up complex communities, while nothing of the sort occurs in those species with free larvie. ‘4 Many similar cases might be given, but we must bear in mind that they are all very different from the one now under examination. In ali sach eases the difference is between the larvie of two distinct species, while in Alpheus we have a similar difference between the larvie 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 advanced 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 the 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 Alpheus heterochelis, in three widely-separated localities, would still be remarkable and interesting. The life history of the North Carolina form of this species is more abbreviated than that of the Bahama form, and the metamorphosis of the Key West form is still more shortened, 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; differences which are much more funda- mental and profound than the mere length of the Jarval life: The various larval forms are described with so much detail in the chapter on the metamor- phosis 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 distinet 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 thag this is the primitive or ancestral metamorphosis which was originally common to all the species. It has been traced in Alpheus minor by me at Beaufort, North Carolina, and by Mr. Herrick in a similar species at New Providence. Mr. Herrick has also traced it at New Providence for Alpheus normani and Alpheus heterochelis. In all these forms the larva hatches from the egg in a form which is very similar to Fig. 2 of Pl. xv1, and very shortly after hatching it» moults and passes into the second larval stage, which is the one from-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 represent the first, second, and fifth thoracic limbs, and posterior to these a long, tapering, imperfectly-segmented abdomen, ending in a flat triangular telson. The locomotor organs are the plumose antenn and the exopodites of the three pairs of max- illipeds. : . ; After the second moult the larva passes into the third stage, which is shown in Pl. Xv1, Fig. 1, and Pl, xvu, Fig. 1. The first and fifth thoracic limbs are,now functional; all the abdominal somites are distinct and movable, and the uropod, or sixth abdominal appendage, has appeared, and its exopedite is functional and fringed with plumose hairs, while its endopodite is rudimentary. The five abdominal appendages have not yet appeared. The first thoracic leg, which was represented by a bud in the preceding stages, has now acquired a flat, basal joint and a swimming exopodite like those of the maxillipeds, but its endo- podite is rudjmentary. The fifth thoracic limb is fully developed and is the most conspicuous peculiarity of the larva at this stage of development. It has no exopodite; its basal joint is not enlarged nor flattened, and its long, cylindrical, slender shaft is prolonged at its tip into a long lance-like hair, whieh projects beyond the tips of the antenne. After its third moult the larva passes into the fourth stage, which is shown in Pl. Xvi, Fig. 3. The carapace now begins to extend over the eyes, 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 and second thoracic limbs. Between the latter and the elongated 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. 352 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. ow After the fourth moult the larva passes into the fifth larval stage, when it resembles Fig. 1 of Pl. xxi, so far as concerns the anterior end of the bod y, from which it differs greatly as regards the telson 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 Pl. xx1, Fig. 1, but the telson and uropods are nearly like those of Fig. 3, in Pl. xx. The telson is narrow aa 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 antennule develops a scale, the antennz 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 Pl. xx, Fig. 2. This life-history is common to Alpheus minor at Beaufort and’ New Providence and Alpheus normani and Alpheus heterochelis at New- Providence, although the latter species presents a totally different life-history at Beaufort. Before it hatches, this form, as shown in Pl. xx, Fig. 1, reaches a degree of development which bears a general resemblance to stages two and three of the es form, with certain differences which are pointed out in the sequel. inmadintoly after hatching it assumes the form which is shown in Pl. x1x, 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 Pl. 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 flagellum of the antenna has elongated, and the other appendages have assumed the adult form. An older specimen is shown in Pl. xx, Fig. 2, and a still older one in Pl. xvu, 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 bas 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, and 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, andl 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 oceuy 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 Guérin’s figure and description 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 found in the brown sponges have only a few large eggs. The eggs from the green sponge hatch in the stage shown in Pl. xxi, Fig. 1. It has rudimentary gills, the eyes are imperfectly covered, the antennules and antenn are beginning to assume their adult form, and the exopodites of the three pairs of maxillipeds are thé 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 Pl. xx1, Fig. 2. The eyes are more completely covered, the antennules and antenne are elongated, the thoracic limbs have the adult form and the rien pods are all functional. In twenty-five or thirty hours after hatching it moults for the aecgua time and passes into the third stage, which is shown in Fig. 8. It is no longer alarva, but a young Alpheus, with all the structural characteristics and pugnacious instinets of the adult. , ‘ In a few cases the development of this species is still more accelerated, and a few eggs from animals taken from the brown sponge hatched in the stage shown in Fig. 8, instead of the stage . Z op alt MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 333 % shown in Fig. 1. The following notes on the variations in the coloration and habits in Alpheus, 3 particularly in A. saulcyi, are taken from a paper ee Mr. Herrick published in the J ohns Hopkins 4 University circulars. VARIATIONS IN THE HABITS AND COLORATION OF ALPHEUS. . 5 Some of the species of Alpheus are usually or even universally found living as parasites within By the water tubes of sponges, and it is extremely interesting to find that individuals of the same x species, living in different species of sponges, may themselves differ 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 once on the oN ; 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 Alpheus, which quarter themselves in the intricately winding pores of the sponge. Hundreds, or even thousands of individuals might be collected from a single _largespecimen. These animals vary from one-eighth to three-fourths of aninchin length. They are ' nearly colorless, excepting the large chelw, 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 eae : are few in number and of unusually large size, their diameter varying from one twenty-second to coe ~ 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 open. 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 ee 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 as vérmilion-orange (Pl. 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 greén 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, ; s out of a hundred or more which were examiried 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. i aig Habitat of Alpheus. | Length of 9 mi of Diamefer. Color. Color of adult, a e. ra + Fa E ey Inches. Inches. Aa 3 Brown sponge.... + 19 vy Yellow (variable). Large chelzw, red, blue, "th eae a j or brown. Be “— ; Green sponge . ---- 14; 347 vs Usually green; in this | Large chelw, always A? : case yellow. orange-red. Ss These two forms, apparently distinct, are seen however, by closer examination, to belong uh 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. z, ¥ The rostrum usually has three spines, but occasionally only two are present, the median one being lost. It is evident that these animals are pertectly protected from outside enemies while within _ the tortuous mazes of the sponge, as their numbers would show. Parasites such as Isopods, how- Ss 334 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. AS a ever, are not uncommon. ‘There has thus been no chance or need for natural selection to act along the line of color. On the other hand, possibly, the Alpheus of the greet sponge does require color protection, since the females are very sluggish during the breeding season, which extends over a good part 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 heads of boring annelids which abound on the reef, and may have a protective significance. This evidence, however, is not very reliable. f 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 differently colored dishes, we never observed any very marked change in the color of the eggs, but these experiments 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 different individuals, but seb 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, represent 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 oceur, 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 different surroundings, growing to three or four times their former size, and the females acquiring bright green eggs, which become a source of protection 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 his time for three years to this subject, and while he carried on the work under my general supervision the results which he has reached are entirely his 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. Herrick’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 the 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 embryonic and larval stages, up to the adult condition. The eggs of each of the thirteen species. which occur in the Bahamas were ob- tained and studied sufficiently to ascertain what are the specific differences in development, and four species were studied exhaustively, in detail. These four are Alpheus heterochelis, Say; A. mi- nus, Say; A. saulcyi, and the Bahama heterochelis. Unless otherwise stated the following notes on the early stages refer to the last 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 be a good subject in which to study the origin aud réle of certain much disputed bodies, which are met with in several Crustacea, the “‘secondary mesoderm cells.” SEGMENTATION OF THE 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 the 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 256 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 aré left in the interior of the yolk. The superficial pyramidal structure is lost; the primitive blastoderm is established, and there now takes place a general migration of nuclei from the surface to the yolk within, but principally, as would be expected, ‘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 into balls. The yolk-ball is apparently formed about the migrating nucleus, but 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 Pontonia domestica, and it is quite probable that the majority of macroura pass through the same phases in their early development. Alpheus minor is anomalous from the fact that the products of the first nucleus instéad 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 prolonged into a reticulum, which encloses myriads of small volk frag- ments, and probably digests them by an intracellular process, after the manner of feeding amcebe. 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 their appear- ance on either side of the long axis of the embryo, as circular patches of ectoderm. Meantime nuclei wander from the cell mass below the abdominal plate to all parts of the egg. Some pass to the opposite side, and take up a position beside the flattened epithelial cells, of what was the primn- itive blastoderm. The majority, however, pass forward and upward 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 embryo. 336 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. PRODUCTS OF CELL DEGENERATION. — " At the beginning of the egg-nauplius 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 uniformly, 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 csophagus 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 function. The endoderm does not appear as a definite layer until the egg-naupiius 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 EYE. 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 delamination, 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 rizht angles to the surface. A dise of cells is thus formed which gives rise chiefly to the eye and its ganglia. The cord of cells uniting the two optic dises 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 SCIENCES. 337 GONODACTYLUS CHIRAGRA, There are few orders of animals of which we are more ignorant than we are of the Stomato- pods. They are well known as museum specimens, and every natural-history cabinet contains one or two, which have been brought home as rare curiosities from distant 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 capture is difficult, and any attempt to study them in their homes is almost out of the question. The habits of Squill are tolerably well known, and in my report on the Stomatopoda, collected by H. M.S. Challenger, I have given an account of the habits of Lysiosquilla based upon observa- tions made at Beaufort, North Carolina; but, except for afew scattered and fragmentary notes in the various descriptive papers, this is the whole of ow: knowledge of the order. During the sea- sons of 1886 and 1887 I was so fortunate as to find in the Bahama Islands Gonodactylus chiragra living in localities which were peculiarly favorable for observing its habits, and I am now able to supplement my report upon the Challenger collections by an account of this interesting species, of which little had hitherto been known, except the fact that if is the most cosmopolitan of the Macroma abounding on the shores and islands of all tropical and subtropical seas. I also obtained its eggs in abundance and succeeded in rearing the young from them in 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 larve of Stomatopoda 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 species in the whole order has, so far as I am aware, been reared from the egg and in this way identified with its specific adult. While the adults usually inhabit burrows in the bottom the larvae swim at the surface of the ocean, and as none of the animals which are captured in the surface net exceed them in beauty and grace, their glass-like pelagic larve are familiar to all naturalists who have had an oppor- tunity to study the surface fauna of the ocean. Their perfect transparency, which permits the whole of their complicated structure to be studied in the living animal, their great size and rapacity, the graceful beauty of their constant and rapid 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 aérated by the currents produced by the abdominal feet of their parents. The eggs quickly perish when deprived of this constant current, and as itis very difficult to obtain them at all, I know of no Stomatopod which has ever been reared from an egg under observation. The older larvie are hardy and are easily reared, but they areseldom 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 assumed the adult form. As I have stated in my report on the Challenger Stomatopoda, I haye reared a young Lysiosquilla 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 larve 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 larve is slow and the larval life long, and as they are as independent and 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 larvee have been arranged in genera and species, but their generic characteristics are quite different from those upon which the adult genera are based, and this is true in a still greater degree of their specific characteristics. As they 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 larvee of several widely-separated species of adults in all stages of growth as well as the larve 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 specific names upon the larve. As I found after the Challenger collec- tion was placed in my hands that it was very rich in larve, 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 ventu.ed to describe the general characteristics of the larva of the genus Gonodactylus (p. 113), and in PI. x11, Fig. 5, of that report I figured a larva which I ventured to call the larva of Gonodactylus. A comparison of that figure with Pl. xv, Fig. 11 of this memoir will show that this determination was correct, for the larva of Gonodactylus 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. ~ CIPFA PTE RR. It. THE LIFE HISTORY OF STENOPUS. By Franots H. HERRICK. This paper is the result of observations made at Beaufort, North Carolina, in 1881 and 1833, and at Nassau, New Providence, in 1887, The marine laboratory of the Johns Hopkins University was stationed at the latter point in the Bahama Islands from March until July of that year, and with the means thus generously. afforded, I was able to considerably extend my studies upon the Crustacea of these coral islands. Professor Brooks found a number of peculiar pelagic larvee at Beaufort, and it is very probable that they represent a part of the life history of Stenopus hispidus. Plates 1x and x, illustrating - two important stages of these very interesting larve, are contributed by Professor Brooks, and 4 the descriptions of these stages are based entirely upon his observations While the material gathered in a sojourn of afew months at the seashore is in many instances incomplete, it seems worth while to bring out this sketch of the Stenopus, inasmuch as nothing was previously known of its development, and indeed but very little concerning the adult form. Stenopus hispidus is, in-fact, generally known to naturalists as occurring only in the Indian and South Pacific oceans. It was at first quoted from the Atlantie (Cuba) by Von Martens (7) in 1872, and it has not since been reported from the Western Continent, so far as we are aware, until we 7 rediscovered it at Abaco, Bahama, in 1886, but any assiduous collector on West Indian coral reefs . must somewhere have hit upon it (v. Appendix I). 7 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 in Baltimore. These are given on Pl. vi. They are especially interesting, since the segmentation is like that of Peneus studied by Haeckel, who relied wholly upon surface observations. ; The ova were immersed in Kleinenberg’s picrosulphuric acid and afterwards hardened in alcohol. This answered sufliciently well for the purpose in hand, although it rendered the eggs more resistant than is desirable. I.—THE NASURAL HISTORY OF STENOPUS. pit The Bahaman Stenopus (PI. vy) measures from 14 to 1? inches in length. All the appendages are long and generally quite slender and delicate, especially the antennie, which give to this fori Rg a very characteristic appearance in the sea. These are snow-white. They are carried widespread 7 and arch outwards in graceful curves. The flagella of the second or outer antenne are two and a as 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 antenne is carried upward, and their inner branch is . dizected 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 2 and bases of the antenn, and in some cases it extends behind the rostrum as far as the mandib- < 339 340 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, While 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 fou. ch 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 different 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 Raraka, one of the Paumotu Islands, and at Balabac Passage, north of Borneo. Both of these, and especially the Samerang plate, essentially agree with our Bahaman specimens, which in color seems to be the more faithful copy of nature. Here the basal joints of the thoracic legs are colored blue as in 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 nee 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 pea Both sexes are of nearly the same size, and, as already stated, alike in color. Being thus brilliantly decorated with the American colors, our crustacean soon acquired with us the name of the “ Bandanna Prawn.” As we see this animal swimming deliberately in the water we are reminded of some strange and fantastically colored insect. It is by far the most showy, and for its size the most attractive, member of that giant family, the Crustacea, which have their dwelling on the reef. One day, when out upon a wading and 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, they 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 clmging 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 into 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 larve, 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 larve 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 by the same substance to the hairs which fringe the bases of the pleopods, chiefly to those of the first and second pairs. i Be wide s Milne- Edw ards feune (4), evidently made ons a specimen in which the natural colors had been removed by alcohol. (See remarks, ete., under Section Iv.) MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 341 After a moult the colors are, as is usual, very bright, and the moulted skin, as it stands intact supported by the antennz, may easily be mistaken for the living animal. These prawns make no sounds and appear to be very timid. The surface of the whole anterior body and of the large claws is thickly beset with tooth-like spines, the points of which are bent forward, and these may be regarded as an admirable protection against being swallowed head 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 antenne or “feelers” and well-developed eyes doubtless warn them of approaching enemies, which, by their rapid angular movements, they may easily escape. The extraordinary development of the eyes in the older larvee (Pl. 1) is remarkable. : The geographical distribution of Stenopus hispidus is very interesting.* H. Milne-Edwards, in his “ Histoire naturelle des Crustacés” (3), gives the habitat of Stenopus hispidus (Latreille) as the “Indian Ocean,” following Olivier (1) and the older writers. In the “ Régne Animal” of Cuvier, third edition, ‘‘ Les Crustacés,” p. 137, he says: ‘‘ We know of only one species, reported from the Australian seas by Peron and Lesneur.” The Samarang naturalists (5) met with it on the coasts of Borneo and at the Philippines in 1843-46. Dana, in 183842, on the Wilkes Expe- dition (6), 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 (Abaco 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 thvrefore expect 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 possesses may have played an important part 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 specifically distinct. Il. SEGMENTATION AND EARLY PHASES OF THE EGG. The prawn, which hatched her zoéa brood on the 4th of June, laid eggs the next morning prob- ably at about 6 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 corpuscles 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 wé have a central nucleus, about which protoplasm is gathered. Around this again is the great mass of yolk, and the whole is encapsuled 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. v1, Fig. 1), while the 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 Bahaman form identical with the Hispidus of Olivier, Latreille, Milne-Edwards, Adams, Dana, and others are given on page 351. 342 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. another egg of the same phase neither cell is quite at the surface, so that the example given in Fig. 1 may be taken to illustrate a tendency, not arule.* The yolk (Fig. 1, Y. C.) consists here, as in subsequent stages, of homogeneous and tolorably uniform green Foy _No vacuolar cavities are to be seen. Second stage.—Four and one- aoe AES 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 ies of which the second represented is the twenty- first. Nuclei occur in sections 21, 25, 29, and 35, none being as yet superficial. A portion of section 21 (Fig. 2) is shown under a higher power in Fig. 3. Third stage.—A fter three hours and twenty-five minutes have passed the third phase is ‘seacked and we have eight cells, around whicb the yolk is superficially constricted into eight corresponding lobes or segments. A surface view of this 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, Pala- 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 flattened, oval disc, shown well in transverse section in Fig. 5 at a, and tangentially in Fig. 4. It contains coarse grains and granules of chromatin, and the enveloping protoplasm radiates visibly but a short distance between the yolk spherules. 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 Alpheus minor. Fourth stage—After another interval of an hour and five minutes there are sixteen cells re- sulting from the fourth segmentation. The blastomeres 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 less 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 ardbaple to me that this papeenaiad cell represents the male and the eentral cell the female pro- nucleus. A small, deeply staining body, which I interpret as an undoubted polar cell (not shown in Fig. 1), lies underneath the chorion, not far from the superficial cell. MEMOIRS OF THE NATIONAL ACADEMY OF SOLENCES. 343 Seventh stage.—In three hours and three-quarters from the last phase the blastodermic cells have spread more rapidly at a given point on the egg, which loses its radial symmetry in consequence. There is thus formed the embryonic area or first trace of the embryo proper. Highth or invagination 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 body, 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 bere segmented into large, irregulaz fragments, each of which is composed of yolk corpuscles similar to those seen in Fig. 4. It is just possible that this fracture of the yolk, which is commonly seen in the eggs of other Crustacea, is artificially produced at least 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 cells have rapidly multiplied 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 effected. 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-abdominal 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 dises, 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 in 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 different eggs, and assume of course that they are all at any given time in 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 differences which may be seen in embryos from the same female.* Time of hatching June 4, a.m.,early. Temperature 80° F. Diameter of egg »; inch. Age ofegg. State of developmeut, Stage. Poy Glirsis ooo deems = 2 cells % pla 5 9 7: eee ee 4 cells. 3 | 14 hrs. 55 min..... 8 blastomeres. 4, | 16 irs ey oes. 16 blastomeres. Gp halouirerc sss es _ = 32 blastomeres. 6 | 28 hrs. 45 min. .... 128-256 blastomeres. Vl ie ee First trace of embryo. 8-| Sagres So So. 2s. oe Invagination stage. 9+ 38s bra\.secscccc cba Pit obscured. 10} 52.hra..........-.. Optic discs and abdominal plate formed. We thus have in Stenopus a type of the so-called “ centro-lecythal” segmentation, exactly comparable to that of Penzeus, and essentially like that which is probably characteristic of a large number of the Decapod Crustacea. The fact that all the protoplasm 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 development of Alpheus. * This is not true of the American lobster, Homarus americanus, in which I have made a very complete study of the segmentation process. In a batchof segmenting lobster’s eggs, there is a decided lack of uniformity. Some ova which afterwards continue to develop, remain with yolk unsegmented until the third or fourth day after fertilization. 344 MEMOIRS OF THE NATIONAL ACADEMY OF SOTENCES., Ill. METAMORPHOSIS, OR PERIOD FROM THE TIME OF HATCHING TO THE ADULT STATE. A. Protozoéa or first larva (length=4™™).—Stenopus leaves the egg as a protozoéa, which may be compared to one of the early larve of Penzus 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 off the shell to uncoil and straighten its appendages, especially the antenne and the long rostrum which was bent under its body. 2 The figure on Pl. x1 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 antenne are partially unfolded, while the rostrum R., is scarcely visible. Drawings of parts of this immature protozoéa are seen in Pl. vu, Figs. 11-16, and the larva itself as it finally appears, 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 sets are developed ou 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 protozoéa (Pl. vi, Fig. 11) is 4™™ long, the rostrum alone being 13™™. 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-fiu, It swims chiefly by aid of its largely developed antenne, which 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 (Pl. vi, 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 (Pl. x1, Fig. 25, Md.) and by its forked telson-plate, adapted for swimming. The forked locomotor tail-fin and large hairy antennz mark the protozoéa stage in Crustacea generally. The carapace is only feebly 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 antenne. 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 hateh- ing is sharply forked (Fig. 13) and is furnished with 6 pairs of rudimentary sets, of which the median pair is the shortest, besidvs 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. por The eyes are sessile. The inner or first antenne (Fig. 25, Al) are jointed, unbranched append- ages. Each is tipped with a bunch of about four long sensory filaments and with a single seta. A single plumose hair also springs from the distal end of the penultimate joint on its inner side. The outer antenne 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 set, 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 Pl. yu, Fig. 15. They are simple 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 Jobe is provided with hairs, excepting the outermost which corresponds, in part certainly, to the secaphognathite. Only a single bristle was detected on this lobe in the specimen from which the drawing was made. The three maxillipeds 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 a MEMOIRS OF THE NATIONAL ACADEMY OF SOIENOES, 345 Figs. 14 and 16, which represent the first and third mavxillipeds of the right side, as seen from below. The endopodites of the second and third pairs possess four joints, of which the terminal one carries set. There is one pair of thoracic limbs consisting of a stout locomotive exopodite, similar to that of the second and third maxillipeds just described, and of a very short, indistinetly segmented endopodite. The latter is armed with two terminal and three lateral plamose hairs on the inner side. B. First zoéa or second larva (length, a=5™"),—Five or six hours after hatching the pro- tozoéa moults into a form which superficially resembles the macrouran larval type. (Pl. Vm, Fig. 17.) The carapace of this larva has grown down so as to cover the basal joints of all the appendages, and it also extends behind them. The rostrum is reduced to from one-half to two- thirds its former size, and does not surpass the antennal hairs. There is still put one thoracic segment with its appendages. All the 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 the latter is greatly developed, and extends to nearly the end of the third somite. The sixth somite, which carries the zoéal telson, is equal in length to the third, fourth, and fifth combined. The fan-shaped telson, viewed from below, is represented in Fig. 20. 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 the first larva, and a non-plumose spine which ends the series; the three rndimentary spurs seen in Fig. 11 being wanting. The eyes, which have acquired short stalks, protrude slightly. The antenne are shorter and are now no longer so important as organs of lecomotion. The terminal joint of the inner antenna is reduced, but otherwise this appendage is but little changed. The outer antenna ends in a stout hook, which 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 palp. It has a serrated edge, and a prominent, inferior, compound tooth (Fig. 18). The inner branch (coxopodite) of the first maxill (Fig. 19) carries three simple and three com- pound spines, while the outer division consists of three segments with stout, plumose hairs, as shown in the figure. ‘Lhe second maxillie (Fig. 21) are considerably altered from the form shown in Fig. 10. There is an outer lobe (scaphognathite), bearing one large hair directed backwards and at least four others which point in the opposite direction. The inner portion is lobulated into six or more parts, allof which are well provided with stiff hairs.* The first maxilliped is shown greatly enlarged in Fig. 22. Examining this in connection with Fig. 14, we find that the exopodite consists of one segment and bears a limited number of hairs (here two) at its apex. The endopodite is segmented and carries numerous hairs, which are continued in small tufts along the inner margin to the base of the limb. The chief swimming organs are the first and second maxillipeds and the first pair of thoracic legs. The inner branch of the latter is considerably developed, and nearly equals the expodite in length. There is a large irregular spot of red pigment 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 protozoéa (Fig. 25), is finally absorbed. It was probably owing to this and to the fact that I gave the lar¥ no food that suited their taste that they never reached the second moult, although they passed a number of days in this condition. In course of several trials the animals at this stage always became greatly crippled by particles of organic matter adhering to their body and invariably starved. For later stages, therefore, connecting this zoéa with the adult, we have to rely upon larve collected at the surface of the ocean. ©. Mysis or Schizopod stage—lIt is evident that the zoéa of the stage B passes into a mysis- like form through the intervention of one or more moults, and we have two larve already noticed belonging to the close of this period. They were collected by at Beaufort, N. C., July 14 and 15, * The distal or terminal lobe represents the endopodite; the lobes next this stand for the basipodite, while the second (?) proximal division at the base of the appendage correspond to the coxopodite. - 346 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 1883. In the Beaufort specimen (Pl. rx) 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 terminates 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 protozoéa, 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 antennz 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 (P1. X) resembling the last, with the addition of several important features. The inner antenne 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 seale is as long as the antennular peduncle. The flagellum of the antenne now appears as a slender filament, nearly twice the length of the scale. Possibly it is formed, as in Penzeus, from a bud-like remnant of the inner ramus of this appendage in the protozoéa. The third pair of maxillipeds and first to fourth pairs of thoracic legs are as in the previous stage, with conspicuous exopodites fringed with sete. 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. BE. Mastigopus 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 mastigopus 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 antenn are biramous. The outer flagellum of the first or inner pair of antennie is the longest (Pl. x1, Fig. 26), and it bears four or five bunches, containing in all about a dozen sensory filaments. The inner branch is a bad. The second antenne extend as far forward as the joint of the first pair, where the inner flagellum is given off. The HES of the second pair is wound into a short spiral coil. - The exopodites of the second pair of maxillipeds are rudimentary (Pl. x1, Fig. 31). The third maxillipeds are now the stoutest appendages, and equal in length che third pair of thoracic limbs. The first and second thoracic legs are slender; the third pair is the longest and thé 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. J¢ thus appears that, as in the Sergestids, the last two pairs of walking legs are shed after the mysis period, to be reconstructed again in the masti- gopus stage. All the abdominal appendages are functional. (PI. x1, Fig.27.) The last segment of the abdo- men is nearly equal in length to the three preceding. It is onal compressed, and more nearly resembles the adult form. In the act of swimming this larva carries the abdomen bent at nearly aright angle to the rest of the body. It is colorless, excepting areas of red pigment at the bases of the abdominal feet, and spots on the lower portions of the antennz and eye-stalks. There is also a transverse band of the same color on the anterior part of the carapace. wr er ee ee a4 Sa Su were! 2 Om Tue oe MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 347 PF. Mastigopus stage.—After it had been kept three days this larva passed through 1 moult, by which only slight changes were introduced, The fourth pair of walking legs is now distinetly jointed, the fifth remaining as a bud. The flagellum (endopodite) of the second pair of antenue uncoils and speedily lengthens. The terga of the first and second abdominal somites bear on the lower lateral margins of each side a short tooth. The larva lived four days without further eedysis. Figs. 26, 27, 30, and 31 are from this stage. G. Mastigopus stage [Pl. x1, Figs. 28, 29, 32-34, Pl. xm], (Length = 9"™).—An older larva, caught in the net on May 7, is shown on P|. xm. The most striking features of this form are the long trailing antennze (flagella of the outer pair), the actual length of which is about 1 inch, which is more than twice the length of the larva. The remarkable eyes which this animal possesses give it a very odd appearance. They are placed at the extremity of club-shaped stalks, each of which is nearly 2" long. The distance between the eyes is 4.7™. In passing to the adult stage the eye-stalks are much reduced. The outer antenne have a short peduncle; along seale, armed with stiff hairs on the inner margin, and a long flagellum, all very much as in the adult prawn. (Pl. xu, and PI. xm, Figs. 40,41.) The first pair of antenne are much less like the adult form. (PI. xi and Vig. 40). Thestalk is longer and more slender than in the full-grown condition. The flagella 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 point one-third the distance from the rostrum to the posterior end of the carapace. The rostrum is short and stout, bent upward, and does not reach beyond a line passing through the vesicula auditoria. The front of the carapace bears also a short dentiform process on each side below the rostrum. These are the only indications of the fature spinous armature of this region of the body. The abdomen and abdominal appendages are 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 provided with a close fringe of inter- locking, plumose hairs, which are Jongest 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 maxille of this larva are represented in Figs. 28 and 29. In Figs. 12, 19, 29, and 38 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 (endopodite) 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), each armed with short tooth-like spines. The second maxilla has also the adult character. (Figs. 28, 42.) It consists of an elongated outer plate (scaphognathite), 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. 30. It consists of a basal 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 (endopodite) bearing a single bristle. Part of the second maxillipeds is shown in Pl. xr and also in Fig. 31 (St. I'.). The exopodite is rudimentary. The outer segments are covered with spinous bristles. We see already a resemblance between these appendages and their adult forms. (Figs. 43, 45,) The third pair of maxillipeds are still the largest limbs. (Pl. x1, Mxp. m1.) The terminal joint bears several long spines. Compare with the adult limb seen in Fig. 46. 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 pereiopods is represented in Fig. 33. This appendage is nonchelate, 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 appendage. (PI. x11, Fig.47.) The terminal joint of the see- ond thoracic limb is shown in Fig, 32; the basal extremity of the third, the fourth, and fifth are given in Fig. 34. The second and third pair are chelate; the fourth is rudimentary; the fifth is stilla bud. The abdominal appendages, excepting the sixth pair described above, are all unira- mous. (Fig. 27.) 348 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. This larva is colorless, excepting large spots of reddish 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 © a lacuna occurs, but it is not difficult to bridge over this gap. The development of Stenopus is especially interesting, inasmuch as it combines certain features of the metamorphosis of Penzeus, 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. vim, Fig. 17) to the zoéa of Callianassa subterranea, figured by Claus.* The length in each case is 5™™, He says, p. 54: Die jungen Callianassa larven besitzen beim Verlassen der Eihiillen eine ansehnliche Grésse, sind sehr lang- gestreckt und tragen drei spaltiistige Fiisspaare, von denen sich das Vordere schon wesentlich der Formgestaltung des spiiteren Maxillarfusses niihert. Der lange Stirnschnabel, sowie die Bestachelung des Abdomens, dessen zweites Segment mit einem besonders langen Riickendorn bewafinet ist errinern an die oben beschriebene larve. which applies perfectly to the Stenopus zoéa, except that the latter has the first thoracic segment with its appendages, while, according to Claus, the first zoéa of Callianassa has not, although his figure is not clear on this point. The rostrum, eyes, antennz, second maxillez, 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, schlauchformigen Anlagen simmtlicher Thoracalfiisse unter dem Integument bemarkbar sind.” Among the Prawns, Penzus has apparently 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). . Palemon (Olivier). Stenopus (Latreille) Léach, Desmarest, Roux, Milne, Edwards, Adams, Dana, ete. Diagnosis of Stenopus hispidus (Latreille).—Body nearly cylindrical. Carapace with prominent rostrum and distinct transverse groove. Outer antennz with long, bristle-bordered scale bent under the inner antennz toward the middle line. Second maxillipeds with epipodite and long exopodite. Third mazxillipeds very long and appendicular, with 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 claws. 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™” (14-13 inches). Thereis little difference 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 pereiopods, 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. Antennz snow white. For further particulars under this heading, see P]. v, and See. 1. The carapace (Fig. 37) presents a marked transverse fossa. It is covered with short dentiform spines, largest on the front. The rostrum is elevated, extending hardly beyond the basil joint of the inner antenn. It ends in a sharp terminal spine and carries six to seven stout, curved teeth on the dorsal median line, besides 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. Claus: “ Untersuchungen zur Erforschung der genealogischen Grundlage des Crustaceen-Systems.” Wien, 1876. Taf. vin, Fig. 1; also Figs. 2-7. : he ee “ Paar) oo kite eee ee eee 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 antenne. The epidermic spines, which are characteristic of the Hispidus, though not confined to this species, are found upon the dorsal surface of the entire body, on the third pair of pereiopods and on the bases of the appendages generally. The first, second, fourth, and fifth pairs of thoracie legs are destitute of conspicuous spines. The spines of the carapace and anterior abdominal terga are bent forward ; those of the fourth, fifth, and sixth abdominal somites and of the tail fin are appressed, stouter, nondentilate, and point backwards. The telson 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 lamelle. The eyes project at right angles to the long axis of tne 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 lingulate appendage, which is supported by a thin, median, and vertical plate. The inner antenne (Fig. 40) bear very long flagella, the disposition of which has already been noticed (Sec. 1). The segments of the stalk are armed with stout denticles, and each division of the - proximal portion of the outer flagellum or exopodite bears externally a sharp spine. The outer antennw (Fig. 41) possess at their base a long, narrow scale (exopodite), 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 spiny, and the flagellum or endopodite 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 farrow divides the cutting surfaces of each. The first pair of maxillz (Fig. 38) consist of an inner (coxopodite) and outer branch (basipodite), with a slender endopodite. The outer division or coxopodite is thickly beset with strong spines. The second pair of maxillz (Fig. 42) are furnished with an elongated plate, the “bailer” or scaphognathite, which is fringed with hairs, an inner lobulated portion (basipodite and coxepe- dite), and an intermediate endopodite, 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 appendages. The innermost of the latter (endopodite) terminates in a stout spine. It consists of two segments armed without by a row of long plumose hairs. The whip-like, appendage exopodite next this is twice as long and is bordered with short hairs. In the second pair of maxillipeds the basil portion consists of several lobules, tufted with hairs, and a small, external epipodite. There is a stout incurved endopodite, with hirsute terminal joints, and a Jong, slender exopodite. A transparent lamella springs from the outer side of the proximal half of the the endopodite, and bears plumose hairs on its free margin. The third pair of maxillipeds (Fig. 46) are long and conspicuous, somewhat less slender than the first or second pairs of thoracic legs. The inner and outer borders are fringed with long hairs. The outer border is deuticulated; the distal extremities of the segments, as of the ischiopodite, produced into asharp spine. The basipodite is small, bearing the persistent and rudi- “mentary exopodite, which is a slender palp equal in length to the ischiopodite. The first pair of dereiopods (Fig. 47) are small, slender, and chelate. The second pair of pereiopods are similar to the first pair, but longer. The third pair of pereiopods, the “ great chelx,” 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 possess 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) end in short bifid dactyles, the terminal 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 differ within the above limits in different 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 in Fig. 44. 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 sete. Measurements (in millimeters). [ Locality: Nassau, New Providence, Bahama Islands. ] Length from tip of rostrum to end of telson ....-..--..-.--- Length of carapax, including rostrum..-.-..--.--.----..----- Greatest breadth, including spines ..-..--.--..--.-.-------- Greatest depth, including spines ...---.-..-...-.-.---.-.--- Length) ofrostrimeers eas seee sesh eee en ee eee Distance between transverse furrow and tip of rostrum --.. - Length of first abdominal tergum -...---.---.---..--.-.---- Length of second abdominal tergum.-.......---.----.------- Length of third abdominal tergum ....-.-......---.-----.-- Length of fourth abdominal tergum..s-....----.-----------. Length of fifth abdominal tergum .....-..------------------ Length of sixth abdominal tergum -....--.-.-.---..-----.-- Lénethy of telsonis sa. te ee eee eee ee aan eae tees Gratest (breadth of telson. --2= ~225.-- sees oes eee eee eee Lieneth of-eye-stalkoac, o-eicae cee eee ee oe een aoe Greatest diameter of eye = --- 2. 2---2-)22 2. o-oo nee one Breadth between 6yes 5--:2 226 cose seme ese ae emtine = Seem Stalkvofinnerantenn® oe jo-co pease ieee ae ee eee Length of terminal segment of the same---..--------------- Length of inner flagellum of the same....-....------------- Length of outer flagellum of the same-_-...--..-..---------- Length of scale of outer antenn® .-.-....-.-.-----..--.-.--- Greatest bread th ofthe same=- = 2 a. eee Length of stalk of outer antenne --...--..-------.----.----- Breadth of stalk of outer antenna .--. ---- yee tee ee eee Length of flagellum of outer antenn® .-...--.-------------- Breadth of flagelluin of same at inner end -...--.--..-..---- Length of third maxilliped__--.--. ---- --.----. .-.2 ==-.---.- Length of terminal joint of the same ........---.---.-.----- Length of basal joint of the same -=-. -2-._....-2:2--.----- Breadth of basal joint of the same... --..--..---..--..----- Length of exopodite of the same -....-...-.--.-..--..----.- Lien eth:oF first:pereiopod soi tir, went ance te oe ate eee Length of-propodus of same.--- 2. - - 55. eo sece enn eee eno ce Breadth of propodus of same.=.. ..2-s--- -5- -- 2 oho one oe - Length of dactyle of Sameé-s= 22-0 - -ae ee eee ne nese sees inae ase Length ofearpus) of same... e.c> seat as aeee ee eee ae ae Hengeth ofsecond pereiopod ene seesaeee > eee eae eee Length of propodus of same.... ---. ---.---.---- ---2 ---- = eng thof dactyle of same... - 2 - 2c Soe - ons nnn aeempeeeee Breadth of propodus of same 22. ------ -- see eee ee eee Héneth of carpus ofsame 7-3. —- - eo <2 oes cee eee cee Length of meros of same ..-.---.---- = aeizkee see peta eo = Length of left third peretopod ....---.-.-----.---- --s-<----- LGN PUO MONO My st ec one Clap win sens ares od a ten SO ee ae Greatest breadth of same with spines -...---.--..-..-.----- Greatest depth of same with spines.....--.-.-.-.-.---.----- Ligne thopaacnvless cP a4 sec siecsciset ot at epee ct cl eee Mencth.ofcarpus Of samotes eo ees eset eco ee eee Greatest breadth of carpus without spines.---..-.-...------ Greatest breadth of carpus with spines ......-.--.----..---- Length of meros of ‘same. = ssc -aeccniscseieace bees cceeeee Length of right third pereiopod ...- 02. ce cece eene cone cues s MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 351 Measurements (in millimeters)—Continued. SOK. cena cece ne enn nce c ew encamenswacn sce sacewneesecescccccwascnenncs fos ? fo t. t baad | Length of chela of the same.......-.--.--.---+..--.--..---- 18 LG acne aes Greatest breadth of same with spines -.-..-.--.-.-.----.----- 5 ME bse eoce cd tee Greatest depth of same without spines ....--.-....---.----- | 4 Stet \ areal mene | eee BlGn Po OM ACuy le OUGAMO Somme eeeseeen sae sen cieldn ce sow fh 08?) c02|5- S222] sacs oe| sconce Width over tooth Of daonyle:—tas4- ee denna tee nm nnd ose. senee>-| 2 -f5-s--.)--<--- fo seat lscamee Length of carpus of right third pereropod --...--.----. ------ Greatest breadth of same with spines.....--...------.------ Greatest breadth of same without spines -. Length of meros of same ..-..-.. --02 ---- «2 - E Length of fourth pereiopod -... 25. c0ese conn cane --newcesee : ERE OL OADbVIE OF GANIC j2-22.0 duinsien|oucdaven 7s Goe~ oes |poke es Length of inner lamella of same....-../---.----.--.-------- 4 Breadth of inner lamella of same.......-..-----------.-----| 1.5 Length of outer lamella of same... ........---.------------ A Length of inner lamella of uropod.-......-....----.-------- 6.5 Length of outer lamella of uropod..........--.--..---22---- Carn Greatest breadth of outer lamella of uropod ............---. 3 ReEmMARKS.—The earliest figure of Stenopus lispidus with which I am acquainted is that of » Olivier, published in 1811 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 he says: “La pince gauche manquoit et paroissoit repousser. Dans un autre, ’étoit la droite qui manquoit et paroissoit repousser de méme.” The next drawing appears in Milne Edwards’s Atlas (3, Pl. 25, Fig. 13) of 1837. Like Olivier’s plate this is crude and faulty. A second and very much better likeness of the Hispidus by Milne Edwards came out in Cuvier’s Le Régne Animal (4, Pl. 50, Fig. 20). This is represented as pale straw color and was evidently made from an old alcoholic specimen. Some of the parts are also figured. Adams’s figure (5, Tab. x11, Fig. 6), already noticed, and his brief description agree essentially with the Nassau form. The antenne are not in their natural position, and should probably be more than twice as long as represented. Of the habits of the species he says: ‘The Stenopus, Sicy- onia, and Peneus, 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 appearing when the surface of the sea is ruftled.” The drawing by Dana (6, Pl. 40, Fig. 8) represents the antenn 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 Stenopus on the plate measures about 24 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-jointed,-and fifth joint 7-jointed; tarsus minute (p. 606).” : This extreme slenderness 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 dog MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. in their natural positions, and in their true relative proportions. In Adams’s plate the fourth joint of the fourth thoracic leg has 16-17 rings, the fifth joint 8 rings. In the Nassau form’the carpus has 10-12, the propodus 5-7 rings. In details like this, where the right and left sides of the same iaaiecine 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 no 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 Unterschied zwischen diesen cubanischen Exemplaren und den indischen anzugeben, welch letztere ich bei Amboina gesammelt habe. * * * Nur erscheinen die indischen im Leben bunt roth gezeichnet, in Spiritus blass orange und mehr hartschilig, endlich scheint Carpus und Hand des dritten Fusspaars bei ihnen minder vier- seitig, doch ist dieser letztere Unterschied gering und fliessend.” He then adds that he would not be surprised if it should turn out that the West Indian form was specifically different from the East Indian. x So far then as we can judge from the figures and meager descriptions in our possession, the Asiatic Stenopus hispidus can not be regarded as specifically distinct from the American form. Perhaps a point of difference worthy of remark is the length of the body from rostrum to end of telson, which is given as 24 and 3 inches by Adams and Dana respectively. None of the Nassau specimens which I have measured were more than 1? inches long. The data upon this point are not conclusive, and, in view of our knowledge of local variations in this respect, can not be regarded as of much importance. It is hoped that the descriptions and measurements which are here given will afford a basis for future comparisons with the Pacific Stenopus hispidus. List of species. So far as I can learn, only five species of the genus Stenopus (Latreille) have been described, viz: (1) Stenopus hispidus (Latr.): Distribution: (a) Indian Ocean, Borneo, and Philippines (Adams). (b) Paumotu Islands and Balabae Passage, north of Borneo (Dana). (c) Amboyna, Cuba (Von Martens). (d) Abaco and New Providence, Bahama Islands. (c) “Red Sea, Indian Ocean, Indian Archipelago, New Guinea” (de Man). (2) Stenopus spinosus (Risso) : Mediterranean (Heller), teste Von Martens and de Man. (3) Stenopus ensiferus (Dana): Fiji Islands. (4) Stenopus semilevis (Von Martens) : (One specimen in the Berlin Zoélogical Museum, purporting to have come from the West Indies. Length 12™™, Von Martens. ) (5) Stenopus teruirostris (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.) STENOPUS LITERATURE. (1) Olivier: Encyclopédie Méthodique, Hist. Nat. Insectes, t. viii, p. 666, 1811. (2) Latreille: Encyclopédie Méthodique, Hist. Nat. Crustaces, Arachnidses, et Insectes, t. 10, rage 1882. (3) Milne Edwards, H.: Hist. Nat. des Crustaces, t. 2, p. 406, 1837. (4) Milne Edwards, H.: Le Régne Animal, Cuvier; Les Crustaces, with Atlas, by Milne Edwards, p. 137. (5) Adams and White: The Zodlogy of the Voyage of H. M. S. Samarang, 1843-6, p. 61, London, 1850. (6) Dana, J. D.: U.S. Exploring Exped. U. S. N., 1838-1842, vol. xiii, pt. 1, Crustacea, p. 607. (7) Martens, oh v.: Ueber Cubanische Crustaceen ; nach den Sammlungen Dr. J.Gundlach. Archiv. f. Naturgesch., 38. Jahrg., Bd. 2 , 1872, p- 143. (8) Heller: Grentaneea des siidlichen Europa, 8. 299. (I have seen only references to this paper.) (9) De Man, J. G.: Bericht tiber dieim indischen Archipel von Dr. J. Brock gesammelten Decapoden und Stomato- poden. Separat-Ausgabe aus dem Archiv. f. Naturgesch., 53. Jahrg., pp. 215-600, 17. Taf., Berlin, 1888. . CHAPTER III. THE HABITS AND METAMORPHOSIS OF GONODACTYLUS CHIRAGRA. By W. K. BRooKs. (With Pl. 1, 11, xtv, and xv.) THE STRUCTURE AND HABITS OF THE ADULT. . This well-known species is found along the shores and islands of all tropical and subtropical seas, and our collections contain specimens from the 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. ~ Roque, Samboanga, Samboanga Banks, Nicobars, Red Sea, Amboina, Indian Ocean, New Guinea. It is subject to but little variation, notwithstanding its very 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 chiragra-like group of species all so close to each otber that their divergence from each other must have been comparatively recent, and in view of this fact it seems remarkable thaf one of these species 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-fifths as long as wide, leaving the dorsal surface of the second thoracic somite completely exposed ; an- tero-lateral angles semicircular and projecting beyond the median gastric area, which is nearly flat, and bounded by two nearly parallel gastric sutures, which are continued to the posterior edge of the carapace, which is nearly transverse with rounded postero-lateral angles; the transverse cervical suture is faintly marked, distané from the anterior margin about two-thirds of the length of the carapace; second thoracic sonfite, somewhat narrower than the carapace, with acute lateral angles; the eight following somites equal in width and wider than the carapace; the third, fourth, and fifth thoracic somites about equal in length; the lateral margins of the third are straight, with rounded angles, and as wide as the dorsal portion; 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 convex; all the abdominal somites have marginal lateral earine, which are nearly linear, with the anterior end only a little wider than the posterior end; postero-lateral angles rounded in the first four abdominal somites, rectangular in the fifth, and acutely pointed in the sixth; there are no dorsal carine on the first five abdominal somites, and no median dorsal carina on the sixth, which carries three pairs of swollen convex lateral carine, 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 carinz project beyond the posterior edge of the somite and lie in the same transverse plane. S. Mis. 94-23 353 354 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 carinz, 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 te 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 farthest backwards; the tips of the intermediates are distinct and reach about half way 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 telson; each of these six teeth carries a dorsal carina; that of the lateral is marginal and nearly linear, while the others 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 intermediate, 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 terminal, largest, and central to the paddle. The eyes are cylindrical, with rounded cornez, and the first and second antenne are about equal in length, and more than half of the 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 BpObs or markings of any sort, as shown in Pl. 117; while the other form, which is copied in Pl. 1, Fig. 2, is more transparent and is delicately inpitind over the entire dorsal surface in an SE but Senatant pattern of greyish-green pigment 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 reticulam. This difference is not sexual, for I found both males and females of each color; nor is it distinctive of age, for, while all the largest specimens were otf’ 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%side in the Bahama Islands, and J 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 reek ov 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- hung by a limestone cliff, from which fragments fall into the water, each fragment is honeycombed by their burrows. A crack or natural depression in the rock seems to be selected by 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. 111), with smooth, even walls and regular curvature, and large enough for the animal to coil up or turn around insideit. Most of the burrows are horizontal, but many are vertical with the opening below, and a few are vertical with the opening above. +9 at On MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 35D The animals usually rest coiled up, with the eyes and antenn directed outwards, just within the mouth of the burrow. They are always on the alert and reach out and snap at every small animal which approaches, even when it is two or three times larger than the Gonodactylus. They rarely pursue their prey, at least in 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 leaving the burrow they seldom go any further. In aquaria they are much more active at night than in the daytime, and they may possibly wander more in search of prey at night than I have ever seen them do in the daytime. They are solitary in their habits, and Ihave never found two in the same burrow. They are pugnacious to an astonishing degree, and their fighting habits, as I have observed them in aquaria, are so fixed and constant that they must be constantly exercised by the animals when at hume. When two specimens are placed together in an aquarium they at first appear to be un- conscious of each other, but more careful examination will show that their eye stalks are in con- stant motion following each movement of the enemy. They soon assume a position in which they are face to face, although they may be on opposite sides of the aquarium, and the constant motion of their eye stalks shows how intently each movement is watched. Soon one attempts to get be- hind the other, but each such attempt is frustrated, until finally they are brought close together, face to face, and soon one springs suddenly 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 the body 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 adaptation to the shape and size of the body indicate that they are constructed by the animals themselves. The habit of bur- rowing in hard rock instead of soft mud is a fortunate one for the naturalist; for, while it is almost impossible to obtain the eggs of an ordinary Stomatopod without using a steam dredging machine; it is easy to get those of Gonodactylus by breaking up the rock in which it lives. While adult Stomatopods are abundant 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 aération which is pro- duced by the current of water which the parent pumps through the burrow by means of the valve- like paddles of the abdominal feet, they die when deprived of this current. The eggs are sometimes obtained, but unless they are found in an advanced stage of development it is difficult to rear them, and I know of no Stomatopod which has been reared from the egg under observation except the Bahama Gonodactylus chiragra. As the pelagic larvee are large and conspicuous they are often captured at the surface of the ocean in the tow net, and the number of genera and species of Stomatopod larve which have been described is nearly equal to the number of adult species which are known, and the opportunity to identify even one of these larve by actually rearing it from the egg is a most noteworthy and important occasion. The habits of the Bahama Gonodactylus afford this opportunity ; 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 carried ashore and broken up the eggs can be obtained without difficulty. At the time of my first 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 Gono- dactylus and a bunch of yellow eggs, which he had picked out of a rock which he had broken to pieces 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 Gonodactylus except the fact that they were found among the fragments of a rock which also contained this apimal. As soon as I saw the eggs and heard how they had been obtained I started for a point where the beach was covered with fragments of coral rock. It was then late in the afternoon and growing dark, but I waded into the water and carried ashore as large a rock as I could lift. After I had thrown this on to a larger rock and broken it to pieces there was just daylight enough to show me 356 MEMOIRS OF THE NATIONAL AGADEMY OF SCIENCES. ( the Gonodactyli 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. 11, 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 prey, 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 armfal, between the large joints of her raptorial claws, and endeavors to escape with them to a place of safety. The promptness with which this action is per- formed would seem to indicate that it is an instinet 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 reverse 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 observe except this species, and the chief use of the burrow of Squilla empusa is for refuge in danger, while Lysiosquilla excavatrix darts down its burrow at the least poe and can not be driven out even when the sand has been dug up on all sides of it. THE METAMORPHOSIS OF GONODACTYLUS CHIRAGRA. 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 Gonodactylus 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 difference 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 larve are very seanty. In 1882 Faxen published an account (Selections from Embryological Monographs com- piled by Alexander Agassiz, Walter Faxon, and E. L. Mark, I Crustacea, Cambridge, 1852, Bull. Mus. Comp. Zool., Vol. 1x, No. 1, Pl. vin, Figs. 2 and 3) of observations made three years before upon a young Squilla empusa which he had reared from an Alima larva; and in a paper which was published in 1879 I described (On the larval stages of Squilla empusa) a series of similar larvze which I had studied while they were alive, and which was sutliciently complete to warrant the statement that they were the young of Squilia empusa, and that this species probably hatches from the egg in the Alima stage. In my report on the Challenger Stomatopods (Report of the Scientific Results of the Voyage of H. M. S. Challenger during the years i873~76, xv1, part XLV, 1886) I have given an account of the metamorphosis of Lysiosquilla excavatrix which I had reared at 3eautfort, N. C.: but except for these observations our knowledge of Stomatopod metamorphosis 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 aftini- ties of theoldest larvie, by Claus (Die Metamorphosen der Squilliden, Abhandl. d. k. Gesellsch. d. Wiss., Gottingen, Bd. xvi, pp. 1-55, Pls. I-vm11, 1871) aud myself (Challenger Rep., pp. 81-114). 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 larve, and gave a scheme or outline of the probable metamorphosis of each genus of adult Stomatopods. = MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 357 Stomatopod larvee or Hrichthidw, as they were named before their larval nature was suspected, have been divided into four genera, Hrichthoidina, Hrichthus, Squillerichthus, and Alima. Of these four the first, Hrichthoidina, is simply a younger stage in the life of the Hrichthus, and the third, Squillerichthus, a tully-grown larva of the Hrichthus type, so that the genera become reduced to two, Hrichthus and Alima. Of these two genera, one, Alima, is much more sharply defined than the other, Hrichthus, which contains a number of divergent types, of which I have shown that five may be clearly distinguished, and I have proposed, for these five, names which indicate the adulf genus to which each corresponds. I have shown that there are many reasons for believing that all Alimi are Squilla larvie; Alimerichthus, the larvie of Chloridella; Brichthalima, the larvee of Coronida; Lysierichthus, the larvee of Lysiosquilla, and Pseuderichthus, the larvie of Pseudo- squilla. The remaining larval type may be distinguished from the Lysierichthus by the shallow- ness of its carapace, which is not at all infolded, and by the position of its postero-lateral spines, which arise very close to the dorsal middle line; while it may be distinguished from the Pseuderichthus larve by the length of the posterolateral spines, which are at least half as long as the carapace, and also by the fact that the telson is wider than long and longer than the long outer spine of the uropod. Tor this larval type, which was represented in the Challenger collec- tion by many specimens, I proposed the name Gonerichthus, giving, at the same time, many reasons for regarding it as the larya of the genus Gonodactylus. Several of these larve were selected and shown in PI. x11, Fig. 5, Pl. xu, Fig. 9, and Pl. xv, Figs. 1 and 5, of my réport; and I pointed out that in all of these larvie, as in the young Gonodactylus, the sixth abdominal somite has a pair of submedian spines near its posterior edge, and its posterolateral angles are produced into acute spines. The telson is slightly wider than long, and its submedian spines are long and slender, but shorter than they are in Pseuderichthus. The telson is notched on the middle line, and there are from fourteen to twenty small secondary spinules on its posterior edge, between the submedians. There is one small secondary spinule internal to the base of the lateral marginal spine, avother internal to the base of the intermediate,,and a third midway between this and the submedian. In Pl. xy, Figs. 5 and 6, of my report, as in the young Gonodactylus, the outer edge of the proximal joint of the exopodite of the uropod is fringed by nine marginal spines, the terminal one longest, and the outer spine of the basal prolongation is much longer than the inner, but not so long as it is in Pseuderichthus. A comparison 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 raptorial claw it must 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 larve are not Protosquilla, as this genus has the telson fused with the sixth abdom- inal somite, while it is free in the older larve; nor are they Pseudosquilla, for they have no movable spinules 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, and the structural characteristics of the oldest larve indicate that they are the young of species in this genus. Led by these considerations I did not hesitate to speak of these larve, in the Challenger 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, upon circumstantial or indirect evidence; and, while the evidence is quite conclusive, I was nevertheless pleased to obtain more positive proof from the larvie which I reared from the eggs of Gonodactylus chiragra. Like many other Crustacea which inhabit the coral reefs, this species has its metamorphosis abbreviated and it hatches from the egg in an advanced condition. It is shown just before hatching, seen from behind in PI. xtv, 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 view. The first five abdominal somites are indicated before it leaves the egg, and the first five pairs of abdominal appendages are fully developed, although the other appendages, with the exception of the mandibles and the large raptorial second maxillipeds, are either absent or rudi- mentary, The eyes are large, and even before hatching they are movable, although they are nearly sessile. : \ 3958 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. The larva, immediately after hatching, is shown in side view in Pl. xrv, Fig. 3; in ventral view in Pl. xv. Fig. 8, and in dorsal view in 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 midde line over the posterior edge of the tenth somite; the somite which carries the appendages which are usually called, in 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 and 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. The antenna consists of a rudimentary exopodite, which is cylindrical and ends in five swimming hairs, although it is of little use in locomotion. The large eyes are subspherieal, nearly sessile, and they touch each other on the middle line dorsal to the antennules. The man- dibles are enormous and the two pairs of maxilla rudimentary, as are also the first pair of maxil- lipeds, while the second pair, the large raptorial limbs of the adult, are well developed, although the dactyle is not folded backwards upon the penultimate joint or propodite. The third, fourth, and fifth maxillipeds, corresponding to the third maxillipeds and first and second ambulatory limbs of decapods, are rudimentary, and the three following appendages are absent, although all the corresponding somites are indicated as well as their ganglia. The abdomen is abont twice as wide as the thoracic region and somewhat more than half as wide as the carapace... The first five somites are distinct and 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, and 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 each side. Its posterior edge is slightly notched and ear- ries Seven or eight pairs of minute movable spines. The newly hatched larvze swim actively about by meaus of their abdominal feet, not by flexing and extending the abdomen, and notwithstand- 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 Nudibranch were in the aquarium in which the first brood hatched, and the larve, nearly a thousand in all, soon settled down upon them, covering them completely, and at once began tearing them off and eativg them. When washed away from them by means of a jet of water they swam about the aquarium for a short 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 larvze, although I could find nothing else that they would touch, and they refused the eggs of ali 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 abdominal somite, with a pair of ostia in each somite. After about sixty hours they moulted and assumed the form which is shown in side view in Pl. xiv, Fig.4. The rostrum and the spines on the posterior border of the carapace have lengthened, but its shape and relative size are about as before. The second antenne 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 appearance in the adult form, and the second pair are much larger than before, and the dactyle is now folded back onto the edge of the flattened penultimate joint. 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 and passed into the third (Erichthus) stage, which is Shown from above in PI. xv, Fig. 9, and in side view in Pl. xtv, Fig. 5. The rostrum is now greatly elongated and reaches to the tips of the antennules. Small anterolateral spines have made their appearance, as weil 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 Pl. xv with Fig. 9. Its lateral margins are nearly parallel, and its greatest width only a little exceeds that of the abdomen. Its posterior border is now nearly transverse and crosses the middle line above the last thoracic somite. -The MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 359 sixth abdominal somite has separated from the telson, but its appendages are not yet developed. The seale of the antenna is now fringed with hairs, and the eyes are divergent, with well devel- oped stalks. The raptorial claws have greatly increased in size and are beginning to approximate to the adult form, while at the earlier stage they closely resembled the chel of the third, fourth, and fifth pairs of maxillipeds of an adult Stomatopod. From this time on to the end of its larval life the young Erichthus of Gonodactylus chiragra presents the characteristics of that larval type for which I have proposed the provisioual name Gonerichthus; and, while the resemblance grows stronger 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. xtv, Fig. 6, from above, and obliquely from below in PI. xv, Fig. 10. The antennulary 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 indicated. Although it is very much younger than the Gonerichthi shown in my Challenger report in Pl. xv, Figs. 1, 5, 6, and 11, it resembles these larvee in the following features as well as in many minor points: The rostrum is long and reaches beyond the tips of the antennules, 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 alittle 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, and its posterior border is transverse. The median dorsal spine, which was carried on the posterior edge of the carapace of the younger larve (Figs. 3, 4, and 5 of Pl. xiv), has disappeared, althouga it persists until a much later stage in the larve shown in Figs. 1,6, 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, Pl. xtv, forms the posterolateral angle of the telson, is the submedian. The posterior border between the submedians 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 6 of Pl. xv of the report the secondary spine can be clearly recognized about halfway between the submedian and the intermediate. With the assumption of the form shown in Pl. 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 Nudibranch eggs were suspended near the surface of the water they quickly discovered and fastened upon them. Up to this time, also, they were peaceful and 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 which 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 survivors would not touch the dead bodies, although most of them soon shared the same fate, and the rest became weak and soon died. ; At the same time that I was studying the growth of the captive larvee I 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, and fifth maxillipeds are now developed and 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 Pl. 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 assumes 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 Hrichthoidina 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 Alpheus, that in other regions, where the adults have different habits, the larva may batch ina 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. ¢ 5 The Challenger collection contains a bottle of very minute and young larvee in the Erichthoi- dina stage, and one of these is shown in Fig. 3 of Pl. x11 of my report. Comparison between this and the newly hatched Erichthus of our species, PJ. 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 Gonodactyli hatch as Erichthoidine is an error. CHAPTER) LV. THE METAMORPHOSIS OF ALPHEUS, By W. K. Brook anp F. H. HERRICK. (With Pls, I, II, IV, XVI to XXIV. ) Section I.—THE METAMORPHOSIS OF ALPHEUS MINOR FROM BEAUFORT, NoRTH CAROLINA. This small species is found in abundance at Beaufort, North Carolina, andin the Bahama Islands, and itis no doubt widely distributed along our southern coast. At Beaufortitis found in shallow vertical burrows in the sandy mud which forms the bottom of most of the land-locked sounds between tide marks. It is also met occasionally in shells, and under loose stones and oyster shells. During its development, between the time when it hatches from the egg and the time when it acquires the adult form, it passes 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 find that other species, such as Alpheus normani, pass through the same metamorphosis, the life history of Alpheus 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 its perfect form by only a few, and has undergone secondary or recent modifications in the others. THE 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 exopodites of the three pairs of maxillipeds, and the plumose hairs on the antennules and antenn:e are not fully extended until after the change. The second larval stage is shown in PI. xvi, Fig. 2, and in Pl. xvu, Fig. 2, and various organs of the larva during the first stage are shown in Pl. xv1, Figs. 4, 6,7, and 8, and Pl. xvi, Fig. 4. In Pl. xvi, Fig. 4, is the antenna of the first larval stage, Fig. 6, the first maxilla, Fig. 7, the second maxilla, Fig. 8, the mandible, and Fig. 4 of Pl. xviu, the first maxilliped. As shown in Pl. xvu, Fig. 2, and in Pl. xvt, Fig. 2, the locomotor organs of the larva during the first and second stage are the plumose exopodites of the antennz and of the three pairs of maxillipeds. There are no functional appendages posterior to the maxillipeds, and the large eyes are freely movable and entirely uncovered. : The larva has all its appendages fully developed and functional as far back as the third pair of maxillipeds. Following these are three bud-like rudiments of the first, second, and fifth pairs of thoracic limbs, and posterior to these a long tapering abdomen, divided into six segments, there being at this time no joint between the telson and the sixth abdominal segment. During the first 361 362 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 Pl]. 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 efficient organ of locomotion. During the first larval stage this exopodite, 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 portion. After the first molt the annulations become less distinct, although the “scale” is still eyligdrical, as shown in Pl. 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 Pl. 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 Pl. xv1,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 exopedite, 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 somewhat 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. xviu, Fig. 4, is telescoped before the first moult, but immediately afterwards becomes lengthened, as shown in PI. xv1, Fig. 2, until it reaches forward beyond the tips of the antennules and antenne. 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 thoracic limb, and has no trace of an exopodite, The hind body is divided by joints into five abdominal somites, behind which is a long und1- 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 transverse. 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 placed 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 iine, 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 easily be overlooked. 4 - ~ > wr ee ey Ae t Te ee ae SRE oe oot da wk, “eer oe A hale Ligeee af Y MEMOIRS OF THE } tet gota ACADEMY OF SCIENCES. 363 = THE THIRD LARVAL STAGE. (PI. xvi, Fig. 1.) After molting the second time the larva assumes the form shown in Pl. xvt, Fig. 1. It is also shown, much less enlarged, in side view in Pl. xvi, Fig. 1. The first and fifth thoracie limbs are now functional, the second is represented by a bud, all the abdominal somites are distinct, and the sixth abdominal appendage has made its appearance. The first five abdominal appendages are still unrepresented, and the endopodite of the sixth is rudimentary, although its exopodite is fully developed and functional. Those appendages which were presentin stage two have undergone little change. 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 marginai 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 annulations which marked it during the earlier stage have disappeared. The flagellum still consists of only one short joint, and the long terminal hair which it carried at the earlier stage has disappeared. The mandibles, maxille, and maxillipeds are about as they were before, but the endopodite of the third mhescllipad 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 in 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 rudimentary knob or bud upon the anterior edge of the basal joint. The second thoracic limb is, as it was at the earlier stage, a two-lobed bud. No buds have as yet appeared between it and the base of the fifth thoracic appendage, which is now fully developed and forms the most conspicuous peculiarity of this stage in the development 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 prolonged at its tip into a long, slender, tapering, simple hair, the end of which reaches beyond the tips of the antenne when the appendage is in the posi- tion shewn in the figure Pl. xvi, Fig. 1. The appendage seems to have little power of motion and it seldom deviates much trom the position shown in the drawing, being usually carried closely 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 1s nearly as long as the first four together, and the sixth is very narrow and almost twice as long as the fifth. The endopodite of the sixth abdominal appendage is present and of considerable size, but it is not as yet functional, although the exopodite, which is not very much larger, is fringed by six long, plumose, 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 disappeared, and there is less dif- ference than before in the relative sizes of the others, but the general form is the same. FOURTH LARVAL STAGE. The subsequent history of Alpheus minor was traced by one of the authors-at Beaufort and by the other at Nassau, but as the stages which follow were found to be almost exactly like the corresponding stage of other species which had already been drawn, 1t did not seem to be advisa- ble to make new figures, and in the remainder of the description the illustrations which are referred to actually represent the larvie 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 Alpheus heterochelis, shown in Pl. xvii, Fig. 3. There is little change at the anterior end of the body, except that the carapace now begins to extend over the eyes, and the ears have made their appearance in the basal joints of the antennules. The mandible has lost its outer branch, and the basal joint of the second maxilla, P). xy1, Fig. 5, carries on its inner edge three hairy lobes. There are now five pairs of swimming appendages in place of the three of stages one and two, and the four of stage three. ‘These five are the exopodites of the first, second, and third maxillipeds 364 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. = and those of the first and second thoracic legs. The endopodites of the maxillipeds are as befcre. The endopodite of the first thoracic leg, which was represented in 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 bud, 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 | fully 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 endopodite of the sixth abdominal appendage, the only one yet represented, is now fully devel- oped and fringed like the exopodite by long, plumose, swimming hairs. The telson has become elongated and narrow, and the spines upon its posterior end are much smaller than before. THE FIFTH LARVAL STAGE. None of the figures of the larve 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 fully 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. Xx1, Fig. 1, from which, however, it differs greatly as regards the telson and the sixth abdominal ap- pendage. The first five abdominal appendages are now represented by buds like those shown in Pl. xx1, Fig. 1, and in Pl. x1x, Figs. 1 and 2, but the terminal portion of the abdomen is nearly like that of Fig.3 in Pl. xx. The telson is greatly elongated, narrow, and its terminal spines are very small. THE OLDER LARVAL 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 antennz become elongated, the antennule develops a scale, the swimming exopodites of the maxillipeds and thoracie legs disap- pear, these appendages assume their adult form, and acquire gills, and the animal gradually be- comes like the one shown in Pl. 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 differences 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. The Bahama specimens hatch from the egg in the stage shown in side view in Fig. 1 of Pl. xv1ir. As this larva agrees in all details of its structure with the first stage of Alpheus minor shown in Pl. xv, Fig. 2, already described, no further description is necessary. THE SECOND LARVAL STAGE. Like Alpheus minus the Bahama specimens of Alpheus heterochelis molt within a few hours after hatching, but they undergo no essential change, and Pl. xv1, Fig. 2, exhibits all the essential characteristics, although this figure was drawn from a specimen of Alpheus minor. The most noteworthy specific difference is in the relative length of the marginal spines of the telson. In the first and second larval stages of both species there are eight pairs of spines, one pair on the outer edge and seven on the posterior edge, as shown for Alpheus minor in PI. xvi, Fig. 2, and for Alpheus heterochelis in P|. xvi, Fig. 3. In both species the pair next the median line are rudimentary and the next pair very small, but the three which arise from the rounded angle of the MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 365 telson are much more nearly equal to the others in Alpheus heterochelis than in Alpheus minor. If, as seems probable, the triangular telson of the macrouran zoéa is a secondary modification of the deeply furcated telson of a more ancient protozoea, then the first larval stages of Alpheus minor are in this respect more primitive or protozoean than those of Alpheus heterochelis. THE THIRD LARVAL STAGE. This is shown from below in PI. xv, Fig. g; and a comparison with Fig. 1 of Pl. xv1 will show its very close resemblance to Alpheus minus at the same stage. The only essential difference between them relates to the rudimentary thoracic limbs. In both species the first thoracic limb has a functional swimming exopodite and a rudimentary endopodite, and in both the fifth thoracic limb has a greatly elongated jointed cylindrical endopodite and no exopodite, 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 after the next molt. THE FOURTH LARVAL STAGE OF ALPHEUS HETEROCHELIS. This is shown from below in Pl. xv, Fig. 3, and there are no noteworthy differences 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 Pl. x1x 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 develop- ment which somewhat resembles stages two and three of the Bahama specimens. There are many important differences 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 of Aipheus minor. Just before hatching it has, like the Bahama form immediately after hatching, three pairs of fully developed swimming maxillipeds, but it also has buds to represent all five pairs of thoracic legs. The antennary scale and flagellum are much more advanced than they are at a much later stage in the Bahama form, and the abdomen is much more distinctly segmented. The larva, immediately after hatching, 1s shown in side view in Pl. xrx, Fig. 2, and in ventral view in Fig. 1. The antennule and antenna are shown on a larger scale in Figs. 3 and 4, and the mandible and first and second maxillw in Figs. 5, 6, and 7 of the same plate. The animal now has all the appendages which are present in the adult, but all behind the maxillipeds are rudimentary, although they all become functional after the first molt, as shown in Pl]. xx, Fig. 3. The antennule, Pl]. x1x, 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 endopodite or flagellum, which is short and rudimentary but much longer than it is in the younger stages of the Bahama specimens. The antenna, Fig. 4, presents even greater differences. The flagellum 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 (Pl. x1x, Fig. 1) are almost exactly like those of the newly hatched Bahama larva (PI. xvut, Fig. 1) or those of the Alpheus minor at the same stage (Pl. XVI, Fig. 2), but the thoracic appendages (PI. x1x, Fig. 1) are entirely different, and the ventral surface of the body is covered by a mass of limbs closely crowded, all pretty well developed, but all as yet SOE Se —_ ae a . 566 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. funectionless. Careful examination shows that there are five pairs (the five pairs of thoracic limbs), and that all but the last pair are biramous. In all, the exopodites are longer than the endopodites, which decrease in length from in front backwards, while the endopodites increase in 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 biramous buds projecting beyond the outline of the body, while the sixth pair are only faintly outlined under 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 spatulate; and of the eight pairs of setze the three pairs whieh in Alpheus minor lie on the lobe at the angle of the telson are not on a distinct lobe, nor do they differ in size from the adjacent sete. This larva molts a few hours after hatching, and at once undergoes the most profound changes, and assumes the form shown in Pl. xx, Fig. 3. Itis no longer a larva, but a young Alpheus. The eyes are almost covered by the carapace, the ear is well developed, and all the appendages are present and functional and essentially like those of the adult. The antennule bas two flagella, each with several joints. The flagellum 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, 5, and 9) have assumed the char- acteristic Macrouran 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 exopodites. The abdomen is now like that of the adult, and the telson (Fig. 4) islongand narrow. An older specimen is shown in Fig, 2 and a still older one in PI. xvii, Vig. 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 specimens hatch in a much more advanced condition than the Bahama speci- mens, aud, 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 specimens is not simply accelerated; it is profoundly modified, so that ne. exact parallel can be drawn between any larval stage of the one and a stage of the other. The statement that the Beaufort specimens pass, before ieaving 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 (Pl. x1x, Pig. 1), is more advanced than the fourth larval stage of the Bahama form (Pl. xvint, 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 in 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 heterochelis which oceur at Key West differ from those which oceur at Beaufort in about the same way that the latter differ from those from the Bahamas, as the metamorphosis appears to be entirely absent in 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 “ i: ; “s MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 367 chelz, and the eyes were nearly sessile. In this case also there seems to be modification as well as acceleration, as Packard says that there were only five pairs of abdominal feet and that these were well developed. It may seem to some that the fact that these three forms present such great and constant differences 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 modifications in the life histories of adults which have remained almost exactly alike. : Careful and minute comparison between adult specimens from Beaufort and Nassau showed the closest agreement in nearly all particulars (v. Chap. v, Pt. First, Section 11), and it has there- fore seemed best for us to regard them as belonging to q single species; the more so since our discovery that different individuals of another species found at Nassau (Alpheus saulcyi) differ from one another during their larval stages in somewhat the same way that the Beaufort specimens of heterochelis differ from the Bahama specimens. Alpheus minor and Alpheus heterochelis are very distinct species. The adults have diverged from one another so far that one could 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 remained almost absolutely unchanged, except as regards the reproductive elements and their product. SECTION V.—LARVAL DEVELOPMENT OF ALPHEUS SAULCYI. An egg of Alpheus saulcyi just ready to hatch is shown in Pl. xx1, Fig.5. The large claws are plainly visible through the transparent shell. The antennz are folded back alongside the body, while the abdominal and closely packed thoracic appendages are directed forward. The telson overlaps the head. . First larva (length, = 735 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 Pl. xx, Figs. 4, 6,7,9, and Pl. xx11, Figs. 1-8,12. In both varieties the animal hatched as a schizo- pod, loosely infolded in a larval skin, but not invariably, as I have noticed that in one or two cases, where females of the longicarpus with very few, perhaps half a dozen eggs, produced young, the metamorphosis was completely lost, the larvze being in a stage corresponding to that usually at- tained after the second molt and represented in Pl. xxi, Fig.8 This is referred to again at the end of the section. To return to the first larva (PI. xx1, 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. Rudimentary gills are present and a remuatt of unabsorbed green yolk is cOnspicuous in the stomach. The carapace 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 ocular spines (Pl. xx, Fig. 6), 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 carapace. A median eye or ocellus is present just below and between the bases of the lateral eye stalks. Both pairs of antennz are biramous and jointed. The antennules (Fig. 8) consist 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 antenne (Pl. xxu1, 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 palpus. The first maxillie (Ivig. 6, 368 MEMOIRS OF THE NATION AL ACADEMY OF SCIENCES. shown with more detail in Fig. 3, Pl. xx11) have adult characters. They are biramous. 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 maxillie (Fig. 6, Pl. xx1) the scaphognathite 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. xxtv. 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 tip. That of the third pair is three-jointed and equa] in length to the exopodite. In the first pair of thoracie legs (Pl. xxi, Figs. 4 aud 7) the inequality of the chele 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 are tipped with rudimentary invaginated hairs. The second pair of pereiopods (PI. xxu, Fig. 1) are chelate, but the articulations of the carpus are not distinet. The third pair 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 until after the first moult. The first pair (Pl. xxi, 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 Pl. XxIv, Figs. 4 and 5. This convenient sexual mark probably appears early, but can not be relied upon at this stage. The second (Pl. xxv, Fig. +) and three succeeding pairs of pleopods have a stout base, an outer blade like that of the first pair, and a shorter endopodite which bears on its inner margin a lobule or palp. The sixth pair, or uropods (PI. xx1, Fig. 9), are not yet free. The inner and smalier 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 notch. Its free posterior edge is fringed with seven pairs of plumose spines, the first or median pair being rudimentary, and the next four succeeding pairs long and nearly equal. "Second larva (length, 48; inch).—The first moult takes place either immediately or very soon after hatching. The animal as it now appears is shown in PI]. xx1, Fig. 2. The principal external changes thus produced are the following: (1) The rostram and ocular arches extend farther over the eyes. (2) Both divisions of the antennules are considerably extended. The flagella of the antenpe are from three to four times their former size and are articulated into twenty to thirty rings, the scale still not passing the peduncle. (5) The thoracic appendages have more of the adult characteristics. The articulations of the carpus of the second pair are distinet. The exo- podites of the first four pairs are functional, and the last pair has grown forward. (4) The pleopods presently acquire swimming hairs; the telson plate is free and the uropods are func- tional for the first time. (5) The last thoracic segment is still uncovered and the eyes are incompletely hooded. Third larva (length, about + inch).—The third larva as it appears after the second moult, which takes place in twenty-five to thirty hours after hatching, is represented in Pl. xx, 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 respects 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 prominent change at the second moult is the extension forward of the rostrum and the ocular spines, which form a hood over each eye. The antennal peduncle surpasses the scale, and its flagellum nearly equals the carapace in length. As in the adult, the large chele are very prominent. The exopodites of the thoracic appendages have dwindled to rudiments. The view of the head of a four-days old Alpheus is shown in Fig. 3, Pl. Xxt. » MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 369 The fourth form (after third moult).— When six or seven days old the third moult is passed, but only slight changes are introduced. The small chela and the inner and outer antenne of this phase are given in Figs. 9, 10, 16, Pl. xxm. The inner branch of the antennules is still relatively short; the basal or aural spine extends to nearly the end of the first joint. The bristle-bordered plate of the antennx has now developed a considerable spine near its outer extremity, a rudiment of which appears in the first larva (Fig. 7). This represents the squamal spine, to which the plate is ordinarily attached, in the adult. The spine is here developed from the plate. The latter nray disappear, as we shall see further on, to be finally regenerated from the base of the spine. The small chela has the adult form. The fifth form (after fourth moult).—These animals moulted the fourth time ten days after hatching. Very little change was apparent, except in size, and beyond this point we did not follow them. e, METAMORPHOSIS OF ALPHEUS SAULCYI FURTHER ABBREVIATED. As was Stated above, the metamorphosis of Alpheus saulcyi may be still further accelerated so as to practically disappear altogether. This fact is illustrated by a young Alpheus hatched in a glass dish April 25 (Pig. 17, Pl. xxi). The prawn (var. longicarpus) was taken from a brown sponge. The eggs, half a dozen in number, were slow in developing. The small chela is shown in Fig. 15. This phase corresponds with that usually attained after the second moult (shown in Fig. 8, Pl. Xx1), with which it corresponds in size and color. All the thoracic and abdominal appendages have nearly the adult form, the exopodites of the former being rudimentary, as in Fig. 8. The large chela is most prominent, being nearly as large again as the smaller one. The eyes are partly hooded, but not so much as the four-day old prawn 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. 94.24 . e 7. ALPHEUS: A STUDY IN THE DEVELOPMENT OF CRUSTACEA. By Francis H. HERRICK. CONTENTS. > Introduction. Part SEcOND—Continued. Methods. IV. The development of Alpheus—Continued. Part First: BHighth stage: Nine pairs of appendages present. I. The habits and color variations of Alpheus. Ninth stage: Eye-pigment formed. II. Variations in Alpheus heterochelis. Tenth stage: Ganglia of ventral nerve-cord III. The abbreviated development of Alpheus and its distinct and completely separated from the relation to the environment. skin. IV. The adult. Eleventh stage: Embryo about to hatch (Al- V. Variations from the specific type. pheus heterochelis). VI. Measurements. Twelfth stage: First larva (Alpheus saulcyi). VII. The causes and significance of variation in Al- Thirteenth stage: Young Alpheus, four to ten pheus sauleyi. days old. ParRT SECOND: V. Notes on the Segmentation of Crustacea. I. Structure of the first larva of Alpheus sauleyi. VI. Cell Degeneration. f - Il. The origin of ovarian eggs in Alpheus, Homarus, VII. The Origin and History of Wandering Cells in and Palinurus. Alpheus. Ill. Segmentation in Alpheus minus. VIII. The Development of the Nervous System. IV. The development of Alpheus. IX. The Eyes. First stage: Segmentation to formation of blas- The median eye of the larva and adult. toderm. General anatomy of the eye-stalk. Second stage: Migration of cells from blastoderm Structure of the ommatidium. to theinterior, The invagination-stage. Arrangement of the ommatidia. Third stage: Optic disks and ventral plate. The development of the compound eye. Fourth stage: Thickening of optic disks. Ru- (1) Origin of the optic disk. diments of appendages. (2) Development of the retina and the Fifth stage: Rudiments of three pairs of ap- optic ganglion. pendages. Optic disks closely united by The eye under the influence of light and dark- transverse cord. Degenerative changes. ness. Sixth stage: The egg-nauplius. X. Summary of Part Second. Seventh stage: Seven pairs of appendages XI. References. - formed. Explanation of figures (accompanying each plate). [With thirty-eight plates. ] ; INTRODUCTION. Fa The observations offered in this memoir were undertaken at Beaufort, North Carolina, in 5 June, 1885, at the Marine Zoological Station of the Johns Hopkins University. But little was accomplished, however, until the next and following seasons, 1886~87, when I enjoyed the advan- tages of this 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, and 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 Providence, and in all these the eggs have been obtained, and in nearly all the larve or first zoéas 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 zodlogy can be fully illustrated. 370 : — Fe -” Te MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 371 The majority of the decapod Crustacea have a long and complicated metamorphosis. That in a few forms the early stages are jumped, so that the young hatch in practically the adult condi- tion, is a remarkable fact, and the discovery of a probable cause for this phenomenon in Alpheus is one of the most interesting 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 Beaufort species, so that there is no work of others to refer to, which bears directly upon our subject. But the literature of the Arthropods is very great, commensurate indeed with the size of the group. During the progess of this work a number of important papers have appeared which are referred to either in the text or in notes. While much is known of the Arthropods as a whole and of that large division of them included under the Crustacea, it is probably true that a great deal of this knowledge is of a very fragmentary and unsatisfactory nature. There is great need for detailed and full accounts of the development 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 supplying the need just men- tioned, but how imperfectly it is unnecessary to say. ' The plan of making observations upon other Crustacea for comparison with the more detailed studies of Alpheus has been as yet ouly partially carried out. The early stages of Stenopus hispidus, Homarus Americanus, and Pontonia domestica have, however, been followed, and less completely those of Hippa talpoides and Palemonetes vulgaris. Spence Bate (3) states that the shortened development of Alpheus was first described in his memoir, with drawings, communicated to the Royal Society in 1876, from a specimen procured in the Mauritius. He named his specimen Homaralpheus, “from the impression that species producing a Megalopa could not be placed in same genus as those producing a Zoéa.” He says: “The orig- inal of my drawing is 2"™™ in length and was procured from a specimen 14"™ long, resembling the figure that I have given of Alpheus minus, Say. An inspection of this drawing (3, Pl. oxxu, Fig. 1) leaves some doubt as to whether there was not an error in referring this form to the genus. The general shape is unlike that of Alpheus, the abdomen being three times as long as the carapace, and there appear to be only three pairs of thoracic appendages behind the chelipeds. Packard (46) in 1881 was the first to describe a shortened metamorphosis for Alpheus heterochelis. In some brief notes published in the American Naturalist of that year, he states that both this and the small green Alpheus (A. minus) occur in abundance at Key West, Florida,in the excurrent open- ings of large sponges. This fact is interesting, and probably significant also, as will be later shown. Packard describes the first larva of this Florida form as mueh further advanced toward the adult state than is the first zoéa of the Beaufort species, according to the observations of Brooks. In fact it more nearly agrees with the first larva of a Bahaman Alpheus soon to be described, in which the metamorphosis is nearly lost. “The Nassau form of Alpheus heterochelis has, as I have recently ascertained, a complete 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 previously done on the embryology of these Crustacea. Several abstracts of the present work appeared in 1887~88 (20-22). P METHODS OF WORK. Several species of prawns, such as Stenopus and Pontonia, repeatedly laid eggs while kept in aquaria, and doubfless 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 phases of development, and were kept under observation in an aquarium for the length of time required. The ova were then carefully removed from the pleopods, and were hardened at intervals of thirty minutes or one hour or a longer time, according to the phase orage of theembryo. By obtain- ing a number of series in this way the whole life history within the egg could be followed, and by 372 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES, 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 werely 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 Kleinenberg’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 killing 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 Kleinenberg 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 punctured to allow the fluid to penetrate the shell more easily and they were then stained entire, in Kleinenberg’s hiemotoxylon. They were afterwards shelled, when this was possible; saturated with paraflin by the turpentine-parafiin method, and were then mounted. While the paraffin was congealing they were carefully placed in position with a hand lens. This last important and often troublesome process was rendered easy by the differential property of the stain, which affects only the embry- onic cells, leaving the ylok, which in preserved eggs is of a light straw color, unaltered. The embryonic tissues are thus made to appear 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 heemotoxylon 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 affected 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 effected by soak- ing the entire tissues in very weak solutions of nitric acid for a considerable length of time. Gaule’s quadruple stain of hzeemotoxylon, eosin, saffranin, 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 unneccessary.* 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 affected 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 aicohol. PART FIRST. y 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 species 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. saulcyi, 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 adopt new methods, especiaily in the treatment of the eggs for surface preparations. In most cases the egg-membranes are best removed by the aid of hot water. ro ‘ ee) ee ee ean >. ™ MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 373 far north as Virginia. From Florida and Cuba nine species are recorded. I have found twelve species of this prolific genus, or about one-half the number described for the whole American con- tinent, inhabiting the beautifal little reef of growing coral called Dix 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 (A. eebsteri Kingsley), first reported from Florida, was also discovered on Green Key reef, a few miles from Nassau. From collections which [ made at Abaco and Andros Islands, I am led to believe that the different species are quite generally distributed in the Bahamas, and as these islands have prob- ably been largely populated from the South, we may expect the same forms to occur at Cuba and at other West Indian Islands, This genus, however widely distributed, is essentially tropical and abounds in all coral seas. Of the great family of the Crustacea which make their home on the submerged reefs of growing coral, Alpheus is perhaps the most prominent and thoroughly charac- teristic. They pop out of almost every rock which is brought up from the bottom, and every 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 animals lead a semi-parasitic life in sponges, or seclude themselves in the porous limestone which forms the solid floor 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 defense 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 which are peculiar, carries the larger of these claws so folded under the body as to be completely concealed. It ean, 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 report is produced. This is true of nearly all the species, and so abundant are many in these islands that a constant fusilade is kept up along some of the shores at low tide. This snapping propensity is shared by both sexes whether in or out of the water, and it is undoubtedly correlated with their pugnacions habits. If two males or females of the same or different species are placed 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 heterochelis are the loudest I have beard from any member of this genus. We frequently kept this species in glass dishes in our room for several days at a time, and sharp reports liké the explosion of a small torpedo or pop gun were heard at intervals through the day and night. It sometimes swims with its large claw so widely opened as to suggest dislo- cation. This weapon then reminds one of a cocked pistol, and the report apparently follows in the same way\that the click follows the impact of the hammer on the lock. I have given this mattter no closer attention, but find that, Mr. Wood-Mason, who is quoted in a notice on“ Stridulating Crustacea” t in “Nature,” (65) has offered another explanation. According to this observer the sound always accompanies a sudden opening of the claws to their fullest extent, and may be caused either by impact of the dactyle upon the joint to which it is articulated or “by foreible 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 by impact, and most likely by the rapid closure of the finger into its socket.t : “This species is entirely new. The large concealed claw suggests a poison apparatus. The “ fingers” are ex- ceedingly slender and sharp at the points. Although kept for over a week in an aquarinm it emitted no sounds. t According to Wood-Mason sound-producing organs in Crustacea were first brought to notice by Hilgendorf, in V. der Decker’s “Reisen in Ost-Africa (Crustaceen),” and were afterwards observed by himself in his dredging ex- pedition to the Andaman Islands. The stridulating organs—scrapers and rasps—may be either on the carapace and appendages or on the appendages alone. {Both Kent and Wood-Mason speak of the sounds emitted by the Alphei as if produced by the extension or opening of the claw. As pointed out above, it is just the other way, the sound following upon the impact of dactyle and propodus, when the tooth of the dactyle is not pulled out of its socket but driven into it. None of the conditions of piston moyement are present. The walls and floor of the pit are relatively soft, while the tips of the claw 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 Alpheus heterochelis the dactyle of the large pincers is a curved blade which shuts down into a groove on the occludent 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 corresponding 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 produced 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 prepared 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 7 claw is not used as a clasper, but as a saber. The sharp external edgeis a weapon of such efficiency that I have seen individuals killed and almost cut in two by a single blow.—W. K. B.) A large brown sponge, Hireinia arcuta, which is not to be mistaken, grows on the shallow reefs and off the shores of all the Bahama Islands which I 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 14 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. Ifa 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 specimen. These animals have an average length of about 12™", They are nearly colorless, excepting the large chelie, 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 inch to one-twenty-fifth inch, and their number from six to twenty. These are most commonly 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 inspection the body is seen to be sprinkled with cells of reddish and yellow pigment. 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 mucous which some of them pour out when broken open. In about nine ont of ten of these sponges one will find 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 are distinguished by their large size (averaging about 23" in length) and uniform color. The females exceed the males greatly in bulk, owing to the large size and number of their eggs. Tn both sexes the large claws are bright red (v. Pl. rv, and for details section Tv). The female is practically inert during the breeding season, 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 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 pigment 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 THE NATIONAL, ACADEMY OF SC] ENCES. 375 Habitat of Alpheus. | Length of 9. aye of Diameter. Color. Color of adult. Inches. Inches. Brown sponge. .- + 19 ay Yellow (variable)... .| Large chelw,red (blue or brown in others. ) Green sponge. --- 1}; 347 vs Usually green; in | Large chelw, orange- this case yellow. red. These two forms, although apparently distinct, are seen, however, by closer study to belong to the same species; but besides the more superficial 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, Alpheus saulcyi, Guérin, it is necessary, for descriptive purposes, to distin- guish two varieties, viz: Alpheus saulcyi, variety longicarpus (from brown sponges), Alpheus sauleyi, variety brevicarpus (from green sponges). These two varieties shade completely into each other by numerous intermediate forms. The longicarpus varies greatly in size and in the color of the body and eggs (besides the other more profound variations mentioned in section V), while the brevicarpus type from the green sponges 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.* y Possibly the variety inhabiting the green sponge does require color-protection, especially since the females are very inert during the breeding season. They are, indeed, admirably protected when exposed on the green surface of sponges, alge, ete. The bright color on the tips of the large claws, which only are protruded from the places of concealment, recall the similarly colored heads of boring annelids, which abound on the reef, but this fact may have no significance. It seems quite probable that if we have in this Alpheus 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 Alpheus known to me within a restricted area. The colors of certain Crustacea, and also the colors of their eggs, are kuown to vary greatly with the surroundings. In the Alpheus, parasitic 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 differently 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 Alpheus heterochelis 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 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 in 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. ; Alpheus heterochelis from Beaufort, N. C., is uniformly of a dark olive-green color, with some red and blue on the appendages. It lives in the beds of oyster shells, which are more or less *A parasitic Isopod, probably a Bopyrus, is found on both the varieties, but is most common with the dweller in the brown sponge.» It appears as a tumid bunch, firmly rooted in the branchial cavity or to the under side of the abdomen. In this connection I will mention another curious parasite which was found infesting the eggs of a single female taken from a brown sponge at Abaco. This is a large, spherical, unicellular organism in the encysted state. The egg, with the embryo, is packed full of them. (v. Fig. 199 and section 1v, Part Second.) In looking over a collection of unpublished drawings of Crustacea, made by the associates of Louis Agassiz and deposited in the library of the Museum of Comparative Zoélogy of Harvard College, I find a sketeh (by H. J. Clark, December 23, 1857) of a Bopyrus taken from the branchial cavity of Alpheus heterochelis. 376 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. exposed at low tide. Alpheus minus 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 bleached 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 chele 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 larvee of a small brood of Alpheus saulcyi, all invariably had the left claw enlarged, and in a smaller number (al! 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 breediug season of Alpheus begins at Beaufort, N. C., about April 1. It covered the period of our stay at Nassau (March to July), and probably began earlier and lasted considerably later.| There the temperature is high and remarkably constant, the annual range being about 15° (temperature of air 70° F. in March, 80° in June), and in consequence 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 Alpheus heterochelis 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 differences, which systematic zodlogists might regard as of specific value, but they are no greater than we have proved to exist among individuals of the same species living in the same sponge. (v. Section V.) The Nassau specimens average smaller, but the chief difference lies in the shape of the small chela. The propodus of this appendage in the Nassau form is relatively shorter and tbicker in both sexes. Both fingers 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 that 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 set. Similar rows of setz occur on the sides of the opposing “ thumb.” Perhaps the most interesting variation which I have observed in the Beaufort heterochelis has reference to the size of the egg. The eggs in this locality have an average diameter of about one “Mr. J. J. Northrop, of Colambia College, while at Nassau in the winter and spring of 1890, kindly offered to collect for me some specimens of Alpheus saulcyi with young. On February 10 he collected six females, five from green sponges, one of which had a brood of sixteen young, and one small female with three larve from the ‘‘ loggerhead” sponge. In the first instance the left chela was the largest in the mother and in each of the sixteen young. Yn the latter, two had the right claw enlarged and one the left. The inference is suggested that when the claw of the same side is invariably the greater in all the young, this character is doubly inherited from both father and mother, but the data are insufficient to settle this point. t Professor H. V. Wilson found this species breeding around Green Turtle Key from July until December. Mr. Northrop found newly hatched young early in February. It therefore breeds the year-through, which is probably true of many of the Crustacea. MEMOIRS OF 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 glued to the anterior swimmerets. These eggs measured only one fifty-third to one sixty-fifth 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 metamorphosis long since laid aside. lll.—THE ABBREVIATED DEVELOPMENT OF ALPHEUS AND ITS RELATION TO THE ENVIRONMENT. Related species, as a rule, resemble each other more in their early stages of development 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 mammals, is spent either in the protecting membranes of the egg or within the body of the parent, 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. Here 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 themselves to this mode of life, and the variations thus entailed have led to the production of the zoéa, a locomotor larva, fundamentally different from the aduit. We may regard the zoéa as a secondary, adaptive form, directly descended from an ancestral protozoéan 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 complicated 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 themselves 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 zoéal stages, formally assumed 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, hatch as zoéa-like and have a complicated metamorphosis. Two species have been discovered, however, which have adopted a parasitic life, and in each 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 nonparasitie and has a complicated metamorphosis, while the same species from another locality is parasitic and has the metamorphosis abridged. We will now consider more particularly the history of these two forms, in order to make a clearer comparison. The species are— Alpheus heterochelis, from Beaufort, North Caralina. Alpheus heterochelis, from Key West, Florida. (2) Alpheus saulcyi, from Nassau, New Providence. Alpheus heterochelis, from Nassau, New Providence. ws ALPHEUS HETEROCHELIS FROM THE BAHAMAS. This species, found at Nassau, exemplifies the development common 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 = } inch).—The three pairs of maxillipeds, each with long exopodites ending in feathered hairs, are the principal locomotor organs. Two pairs of rudimentary 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 stout jointed stalk, the terminal segment of which bears four 3 sensory filaments. A long plumose spine springs from the extremity of the second joint on the inner side. The antenne are biramous, the two branches arising apparently out of a common basal segment. The outer division is a seale-like plate. It bears on its extreme inner border a row of plumose hairs, eight to ten in number. The endopodite is slender and shorter than the scale. It terminates ina - short spine or denticle, 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 zoéal spines, the number, relative size, and position of which vary slightly in the different species. There are in this case eight pairs of these spines. The first or median pair is rudimen- i tary; the second 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 appendages 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. ALPHEUS 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 Alpheus minus. 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. The 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 hatching. Theantennz 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 flat. spatu- late at the end, much as in theadult. There were five pairs of abdominal feet or swimmerets, each with endopodite and exopodite, like those of the second larval stage of the lubster.” 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 characters, very marked in the first larva, are all acquired in twenty-four hours 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 Alpheus saulcyi 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. The eggs of the Alplei, 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 — ae Re ete se MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 379 size and number of the eggs. These and the other facts which we have been considering are given in tabular view below: Species. Habits. Metamorphosis. eee eee Lae 4 f ) | Inch. Inches. Alpheus minus (from Beaufort).| Non-parasitic - ...--- Complete ...-.-.. -- "500 ae | 4-1 A. heterochelis (from Nassau) ...|....do0 ...-....-..----|---- 0 BE eS 300-500 toads | 8_]} A. heterochelis (from Beaufort) .|....do ......-. .-| Abridged. -----| 150-300 ty- or 1-1} A. heterochelis (from Florida) .-| Semi-parasitic....--.}....d0 -...--...---.|.--------- {ne ed PEAR coe A. sauleyi (var. breyircarpus) ...| Completely parasitic.| Nearly lost ...-.- -. 100-350 vr | 4-1} A. sauleyi (var. longicarpus)....|....do .........---.--| Completely absent 5-20 v5—vy | i ll (in some cases). / * Number not accurately determined. 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 number of eggs vary somewhat from the numbers given above, which are the average limits. In the genus Aipheus we thus have several stages in the abbreviation of the metamorphosis between the macronran zoéa stage and the adult form. What is the cause of this gradual suppres- sion of the zoéa like form? The 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 the young might be hatched fitted to live in an environment similar to that of the adults. It the zoéa brood were swept ont 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 larvie 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 newone. (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 ; consequently it has retained undisturbed its complex larval development. The Floridian form has become a parasite, and its metamorphosis is accelerated as the result. From this the Beaufort Alpheus with its less abridged development has doubtless been derived (the species extending north- ward from the Gulf of Mexico), and it is within the possible, at least, to suppose that in this form the metamorphosis, once lost by parasitism, is now being reéstablished. No fewer than three species of macroura, together with the Alpheus above described, occur in the large brown sponges (/Hireinia arcula) of the Bahama islands. These (one of which is also an Alpheus) live in the larger oscula, are less regular in their oecurrence, 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 sponges at Key West, but in this case we do not know, first, whether this is a fixed or only a transient habit, and secondly, we know nothing of its metamorphosis under these conditions. Thus while in Alpheus the abbreviated metamorphosis may be explained as an adaptation to a parasitic mode of life, the question is probably often complicated by conditions which are not easy to determine. There is a general tendency among the higher forms of certain groups, as in the Cephalopods among the Mollusca, to reach the adult conditions rapidly by omitting some of the early embryonic stages. * An egg of A. sauleyi var. longicarpus, just ready to hatch (Pl. xxt, Fig. 5), measures ;45 by fy inch. t The Alphei which inhabit sponges are commensals rather than parasites in the strict sense. They derive pro- tection from the sponge colony, and receive the benefit of the circulating currents of water which are set up within it, 880 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. An abridged larval development has been attributed to the following macroura: The lobster Homarus americanus; the crayfishes, Hippolyte polaris; Paleemonetes varians; Palemon potiuna; Pa- lemon adspersus and Briphia spinifrons (as first observed by Rathke, according to Packard); Bytho- caris leucopsis (observed by G. O. Sars, according to 8S. I. Smith); Alpheus heterochelis, and A. sauleyi. To this list we must probably add the names of many deep-sea decapoda, Munidopsis, Glypho- crangon, Elasmonotus inermis, Sabinea princeps, Acanthephyra gracilis, and Pasiphaé 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 (Parapasiphaé sulcatifrons,) which carries only fifteen to twenty eggs, each of which is more than 4 millimeters in diameter, and approximately equal to a hundredth of the bulk of the animal producing it—a case in whieh the egg is relatively nearly as large as in many birds!” ‘Although the great size of the eggs,” says Prof. Smith, “is highly 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 in closely allied species, even where both are inhabitants of deep water (59).” The larval life of both terrestrial and fresh-water Crustacea is generally short as compared with that of marine forms, and the case of the crayfish may find an explanation in 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 Paleemonetes 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 larvie, and, like them, swim at the surface of the ocean. S. I. Smith (58) and Ryder (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 in 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 Ryder, 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 theantenne are somewhatrudimentary. 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 fourth molt (fifth stage) the young lobster, now 14™™ long, quite closely resembles the adult. It swims more on the bottom. The flagella of the antennz 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 swimn- merets are developed in the seventh stage, at the end of which ee 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 corresponds with the third larva of Alpheus sauleyi (Fig. 8, Pl. XX1) 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 Palemonetes varians are very different, the adults of these two varieties resemble each other very closely. Much more remarkable is the case of Alpheus heterochelis, even if we regard the Nassau form as a distinct species, and that of Alpheus sauleyi, where we have the same species living in the same sponge, hatching now as a larva and now as a form possessed of all the external adult characters. Both the long and short metamorphosis has been attributed to the West Indian shore crab Gegarcinus. This highly colored crab (Gegarcinus ruricola) is very abundant 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, Trichodactylus and dAglea (‘mountain crab”). . : “A delicate moulted skin, which is easily overlooked, either comes off with the egg membranes at the time of hatching or is shed shortly after, as my own observations have clearly shown. MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 381 The habits of the hermit crabs, though secondarily acquired in comparatively recent times, have had no tendency to shorten the larval period. This is also true of the Pinnotheres. Simi- larly the commensalism of such forms as Pontonia domestica, which lives in the mantle cavity of several species of Pinna, has in no way affected its er atopiant IV.—THE ADULT. The Alpheus whose development has just been traced was provisionally named Alpheus pre- cox (22), in allusion to its greatly accelerated metamorphosis. It has since been found to agree in most particulars with the description and figure of Alpheus saulcyi given by Guérin in Ramon de la Sagra’s History of Cuba (18). In Guérin’s drawings the long spine (squamal spine) of the antenne 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 carpus of this appendage is one of the most constant of specific characters. If these figures are accurately drawn, the two forms in question are certainly not specifically identical; but though not at first able to satisfy myself on this point, or to decide from the short and imperfect description, it seemed best after further study to adopt Guérin’s name. The systematic zodlogy of the genus’ Alpheus is in a very unsatisfactory state, and in the absence of adequate and well executed drawings, and too often with only vague or general descrip- tions, the attempt to idengify 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 sauleyi resideut in certain ty 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 spines; barely surpasses the latter in length; without 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 propodus; 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, on 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", 4; largest, 42™", 2; average length, 25 to 30™™, Females exceed the males a little in length, and greatly surpass the Jatter in size when swollen with their eggs. Color: The color of this form is shown in Pl. rv. 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 maxillipeds. Body, pale, translucent, with scattered cells of reddish or yellow pigment, subject to quantitative 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 iead 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 2,33". Number of eggs attached to abdomen, 347, The male in this case also, after a moult, was apparently colorless, contrary to the rule that upon molting the colors 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 long, feebly convex above, without crest. The orbital spines are separated from the rostrum by a shallow superficial groove, and the marginal notch on each side has a regular -shaped outline. Length of spines and width of notch are slightly variable. The lateral compression of carapax is not marked. Frontal angle (angle made by middle line above and below rostrum, greater in 2 thanin ¢. 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 depression. The compound eyes 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 permanent ocellus (P]. xx, 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, Pl. xx111) 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 in 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 under side of the latter the sensory filaments (olfactory sets) are borne, distrib- uted in seven to ten bunches of two to three in a bunch. The antenne (Fig. 8, Pl. Xx11) are composed of three parts—a basal portion (protopodite), which carries a squamous spine (exopodite), and on its inner and lower side a léng three-jointed stem, which 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 spurs 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 plumose sete. The antennal stem or peduncle consists of two short proximal segments and along 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, Pl. xx11, and in Pl. tv. The mandibles (Fig. 3, Pl. xx111) are strongly bifureate, 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 (Pl. 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 (P]. xxtv, Fig. 9) is composed of three portions. (1) The long respiratory plate; the “bailer” or scaphognathite, fringed with a row of sete. (2) An outer and lobulated 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, Pl. xx111) are made up of a long, strap-shaped exopodite, with jointed setz at the extremity and a small setigerous plate at its base; a small, two-jointed endopodite, protopodite, and 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 (coxopodite). The epipodite is an oblong plate, united by a short stalk to the protopodite. en eS Me, See MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 383 The second pair of maxillipeds (Fig. 6) has a long, strap-shaped exopodite, like that of the first pair. The endopodite is incurved, and segmented into at least four parts. The dactylopo- dite or terminal segment is the longest, and is thickly studded with serrate bristles and setie. There is a small oval epipodite. The third pair of maxillipeds (ig. 5) consist of a basal piece (coxopodite) and a long two- branched appendage. The large branch consists of three distinet segments—a long proximal one (basipodite (?) and ischiopodite), a shorter one (meropodite), and a long terminal segment (carpo- podite, propodite, and dactylopodite). The exopodite springs from the base of the first segment, and is about equal to it in length. The lower surface of the two terminal joints is covered by numerous transverse rows of serrated bristles, and the end of this appendage is armed with several spines. , . The first pair of pereiopods or walking legs bear the great chelw (‘“hands” or “‘shears”). ‘he chelz are very unequal. Large claw (relatively larger in ¢) smooth, slightly twisted; outer and upper border sometimes marked by a linear crest; several spurs or tuberosities near the articular surface of the dactyle; 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 propodus 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 fingers barely overlapping. Dactyle sometimes overreaches propodus. Thumb (or extremity of propodus 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, Pl. xxrv) usually carried bent downward. Fingers nearly equal; three- fourths as long as palmer portion of hand; bent slightly downward and outward; propodus sub- eylindrical ; half as broad as long; tip simple or slightly bifid. Small bunches of set on fingers. Second pair of pereiopods (Fig. 1, Pl. xxi): The characters of this appendage appear to be remarkably constant and of considerable specific value. They end in a small claw, the fingers of which are provided with bunches of long hairs. Carpus superficially constricted into five rings or segments. First or proximal segment nearly equal to 2+3+44+5. Second, third, and fourth of nearly equal length; fifth equals 2+3. The third, fourth (Fig. 2, Pl. xxii), and fifth pairs (Fig. 1, Pl. xxrv) of walking legs are similar to each other, the fifth pair being shortest. Each ends in a short, horny dactyle which is bifid at apex, the primary claw bearing a smaller secondary tooth at base. Propodus little shorter than meros in the fifth pair, and carries numerous bunches of short sete on its under side. There are also found in this region of the propodus four to six stout appressed spurs. The first pair of pleopods is specially differentiated 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. 6. In the unmodified limb the protopodite carries as usual the two branches—endopodite and exopodite—each fringed with long sete. 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. The exopodite is short and the inner branch a small rudiment. In the female (Fig. 5) the modification has not proceeded so far. The endopodite is here the shorter and has no secondary branch. In the very young forms (first larve) these appendages appear to be nearly alike in both sexes (Pl. xxu, Fig. 5). The uropods or sixth pair of pleopods hardly require special notice (Pl. 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 closely set plumose sete. V.— VARIATIONS FROM THE SPECIFIC TYPE. We are now ready to consider the remarkable variations which this species undergoes. The form just described was taken as typical, and the largest adults invariably belong to it. (1) Variety Longicarpus: This is the widest departure from the first form or type and is very commonly met with in the brown sponges already noticed. Probably more than 90 per cent of the 384 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES, individuals found in them belong to this variety. The color variations of this form have already been given in section I. The rostrum is sometimes wanting, as in the individual from which Fig. 11, Pl. xxu, was drawn. This variation has been noticed in other species and is interesting, since the absence of the rostrum is a constant character in a closely related series of forms, which are placed by Dana in a separate genus (Beteus). These variations indicate that the uniform presence or absence of a rostrum is a specific and not a generic character, as has already been shown by Kingsley (29). The structural points of difference between the longicarpus and the other form lie chiefly in the antenne and first pair of walking legs. These may be seen by a comparison of Figs. 11, 13, 18, Pl. xxi, and Fig. 2, Pl. xxtv, with Figs. 4, 8, Pl. xxm1, and Fig. 3, Pl. xx1v. In the first pair of antenne the aural spine (Fig. 11, Pl. xxi1) is scarcely more than half the length of the first segment of the stem. It is blunt and somewhat ovate in shape, as seen from above. (2) In the other form (var. brevicarpus) the aural spine (Fig. 4, Pl. xx1i1) has a different shape, and is relatively nearly twice as long. In this case it extends beyond the first segment to two- thirds the length of the second. The second or outer antenna of the longicarpus is armed with two spines at its base (Fig. 11, Pl. xxm1); an inferior and outer basal spine, and a slightly longer one, the squamous spine, articulated to the joint carrying the latter. Thereis no scale. The basal spine is rather more than one-half the length of the antennal stalk. There may be present a small tubercle on the upper surface of the segment bearing the basal spine, near the articulation. In variety brevicarpus (Fig. 8, Pl. xx111) the squamous spine is stout aud reaches nearly to the ° end of the antennal stalk. There also springs from its inner and proximal margin an elongate plate or scale, the inner free edge of which is fringed with plumose set; scale not quite as long as spine. The inferior basal spine not one-half the length of the squamousspine. There isa rounded or pointed tubercle over basal spine near the joint. ; The small chela of the first pair of thoracic legs of the longicarpus (Fig. 2, Pl. xx1v) 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 bent or hooked tips. The carpus is ee very long, quite as long as the palmar portion of the propodus. In the brevicarpus the small chela is long and somewhat narrower (Fig. 3, Pl. xxtv). 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 differ noticeably from the brevicarpus type. (Com- pare Fig. 5, Pl. xxv with the figures on Pl. tv.) 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 and below in a rudimentary fictuttib with claw- ike tip. Dactyle overreaches propodus, and its inner margin is not concave, or but slightly so. These two forms, differing 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 in sponges and from porous rocks on a number of reefs, has resulted in the discovery of a complete series of intermediate links. These connecting 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 aboutfive per cent of the collection made at different points near Nassau present intermediate characters.* More fully stated, the noticeable points of variation are as follows: (1) The relative length of the antennular stalk and aural spine; (2) the lengths of the antennal 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 atarDys of the small cheliped ; B) the general shape and character of the large *While the species live, as a rule, in the interior of iy green and 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 individuale possess intermediate characters between the two varieties just described, 7s ati al mo ae | ae ; ‘. " ‘ol MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 385 claw. (1) With respect to the first point, we meet with a perfectly graduated series between the two extremes (Figs. 11, 18, Pl. xxu, Figs. 4, Pl. xxi). (2) The same is true of the relative lengths of the antennal spines, the scale, and peduncle (Figs. 11, 13, 14, Pl. xx). 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 arudimentary scale. In Fig. 13 this seale is further deveioped. (3) Great variation is seen in the small chela. The fingers of this claw may each end in two or three prongs, or one in two, the other in three, or the tips of the fingers may be simple or merely notched. The tuft of peculiar set on the dactyle may be reduced or wanting. (4) Various stages between the long and short carpus are observed, and (5) slight variations not easily described are constantly seen in the relative size, shape, and other characters of the large chela. ir These variations are shown in a general way in Table I. (For detailed measurement, v. Table II.) The fifteen cases here recorded were selected from upward of seventy-five, in a large number of which the variable parts were drawn for more careful comparisons. TABLE I.—Showing variations in Alpheus sauleyi and the intermediate stages between the varieties brevicarpus and longicarpus. = | No. | Sex. Habitat. Length. Aural spine. Squamous spine. mm. 1 & Green sponge.. .----- 29.7 | Extends } length 2d seg- | Extends nearly to end of antennu- ment of antennular stalk - lar stalk. 2 Cpl RC Biel a ae Be, [ht 3 To 41, 2d segment.-.-.....-. Do. 31 ieee Brown sponge... ---- Do. 4|_ 2 | Green sponge--..-.-.... Do. 5] @ | Rocks; Dix Pt. reef--. Extends nearly to end of antennal stalk. Gate Si 23500) Beadenvceacen= LOC AS | oe ace = do ...-..--.----------| Not nearly to end of antennal stalk. 7 Obed, see Mera an reer eat = 11.6 | 1. of Ist segment. .----.-.-.- Do. 8| fg | Rocks; Hog Id.reef..| 10 | Over 41. of Ist segment --.-] #1. antennal stalk. 9 eel eee ith ee ee a 10 Nearly to end 1st segment..| More than # antennal stalk. 10| ¢ Bopks Green Key 9.5 | #1, Ist segment..---...--.. Nearly to end antennal stalk. ree 11 g | Brown sponge ....-.. 17.5 | Nearly to end Ist segment-.-| # antennal stalk. 117 ey ia RE SC ee Se corte ihe a ESe ee GOpre. aelata asap ana More than 4 antennal stalk. 13 - Rocks; Dix Pt. reef. - 9.5 | 4 1st segment............-. Do. 14 a Brown sponge -..----- O75 fia 3. OOo Saar aes cee #1. antennal stalk. 15 2 Reef rocks: i-. st-c2 ll Nearly to end Ist segment. -| 3 1. antennal stalk. No.| Inferior basal spine. . Squawe or scale. Car us of Fingers of small chela. Remarks. 1 | 4lengthsquamous | Scale as long as | Short ---.| Tipssimple; notuft | Type of var. brevicarpus. spine. squamous spine, on dactyle. 2 | Less than 41. squa- |..-.do ..... sew en as on nO a ato = Tipssimple; notuft.| v. drawing, Pl.1v. mous spine. DB lsnckOd wasoae =u ae Scale nearly as |-..do ...-...|.... do ....-...----.| Claws dull red. long assquamous spine, APS Ld sce. apa keene Seale somewhat |..-do ...-..].... Orns oScnee sons shorter than squamous spine. . 5 | Nearly 4 1. squa- | Secale not quite 1. | Long.-.---. Tips simple; rudi- | Combines characters of mous spine. squamous spine. mentary tuft. both varieties. (6) 255200. s-sescee-eree Smallandrudimen- |.-.do ..---. Prongs; tuft on tary. dactyle. 7\, 41. squamous apine:|- 2.00) oe eos eeem ol omnis Hawn teenies oe en = mone 8 | $1. squamous spine.| Rudiment -.--..-.-. Short -....| Tipssimple; notuft-.| v. Fig. 13, Pl. xx11. a eee eee teenies ~ > Brow : Ot Eee ees OPP a ece Meeer Poy ee -- |sponge|sponge.|Pix Pt-|Green Key|Green Key lsponge. Dix Pt. - — ~ - - | [3 vs ESE oe eae ee ee eee eee 8] roa 9 f fe) ood DA: AVRO SN Int CER DIE rosacea lo nna. wi och ae dcnstw ives ceaee ue ine tes 2 1 10 6 Length of propodus of large chela .......-..-.----- 15 at | santos : Bait 4.5| 6 BK! Length of same to spine at base of dactyle.....--- 11 11 5.1 4.4 ea | ee eR st Greatest width of same .......--.....----5.----- SeGi inated. |ooe Ben Pats) 2 ye (El as Greatest uepth ofsamie -fe!ls 2.2 i225 85 4 BG | eee eee 4 2 2 Width of same at spine, at base of dactyle....-.-. rial ey, We eee Dae A eetendecualosaseelesotec Length of ‘‘ thuml ” of propodus. ...-.....--.---- eg Stel ae | Se onl eee ° PenpihOnagey lec. cse<\.c once csecee ce Sets ess 4 6 2 2 1 Pie ee Width of same, over tooth ...-.....---...--..---- 3 Cn Ber 1 pioneer &) Peet ry) ener Length of carpus of large cheliped, on upper me- ; Me Gees alec ome Satin sacs anea ns eae ec 2.6) 2.4 Length of meros of same. ..-.......-..----..----- 5.5] 5.3 Greatest width of meros of same..........-...---- 3 2.6 Length of propodus of small cheliped-....-...---.. OA eG Length of same to articulation of dactyle-.-...--.- 4 3.1 Greatest width of same -22--.<2o5-6.2. 2.2 2 2.4| 2 Greatest depth of same -.-..........---......--.- 178) eee Length of dactyle of same ........---..---------- Br or es Width of dactyle of'same <7. --..........2-..-.---: 1 0.9 Length of carpus of same .-......---....-.. -.--.] 2.3] 2 Length of meros of same. .--.-- Sere ae 6 5 Greatest width of meros of same....-..----..----- 2.7 | 2.5 Length of carpus of second pereiopod..--.--..-.--.- 7 5.5 Length of first segment of carpus of same -...---- APA ee eres c's Length of fifth segment of carpus of same --------| 1 |...2..|..---- Length of second, third, and fourth segments of GATPUR OL SANG Reena ois on eco esan ss sue desice~ s.2= 5 ee ee Sheree oa eee ites dle at oo ole ces lien ae oe Length of propodus of same..---.---------------- DoW ig a[ sae ate 2 1 1 UR ssc Length of meros of same-...--...-..-----.-------- HAN eer a (SS 2 a A oP eee eee cei c Length of propodus of third pereiopod ..-.--.--..- 5 LAS |: Sy Ee SS Se) AOS 8 ee Length of carpus of same...-...-..-.-----.------ Deen eney feaeee = fase eenaee | senerstnesi| somata! omereme Length of meros of same. ..--...----.------------ Grdelie. Os ilps | oes Sabet tepow see's [eecee an ae Length of ;,rotopodite of third pleopod....--. ---- 6 Udine = | Oe Ses es BES Bar nee eee Width OP Bam: fo oee tence an aes eeehacaas vocee= =e TA \6e8T is Le e ME el ae SS ee ey Pee Length of endopodite of same-...----..----...----| 8 Cena Ns 1c] Re ee ol |S ease Boece Greatest breadth of endopodite of same ...--.-.--. Le | EL ERAS oe eat ara eS et a eS Length of exopodite of uropod....-..-----.------ Gaye ro Tt EN OO Se oe Ser ee ceee Mesricc Breadth Of samess-s-apasnsseeeoetean ses sencee ADA Lh Caliteceae| = 24 Ste oy | see npn|se seal aseas Length of endopodite of uropod ...-- aerate te 5 Uedilseeeeel cea scees len ustaval ue scce| mone Breadth of same? seca sasee snes - sence ss watiec se 3.5-] 2.9 | Be ee eet ocaee lc cow davies | tekae| meee VII.—THE CAUSES AND SIGNIFICANCE OF VARIATION IN ALPHEUS SAULCYI. If we consider Nos. 1 or 2 of Table I as representing the nearest approach to the mean of the species, Nos. 5 to 15 must stand for individuals which have fluctuated 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 | find a still greater percentage of males. There can be little doubt that in those 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 than one-half that of the brevicarpus type. The brown sponges teem with a population of under- sized forms, nearly all of which are aberrant, and none of those which were examined exceeded the length of 17.5", which is considerably less than the average for the type. How 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, departing from the standard of the species and becoming different at different periods of its life, or do individuals deviate from the jean of the species, each along its own line? Further, are the variations congenital? While we 388 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. are not prepared to answer these questions as fully as we could wish, yet the facts are sufficient 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 larve of these prawns the external antennz have a well developed scale, and it is thus clear that this organ may degenerate and apparently disappear, to be reconstructed again at alater period. The variety longicarpus (No. 15, Table I) has no *‘squame,” although it is present in the young (Fig. 7, Pl. xx11), and the cases in which the organ is seen in various stages of development (Figs. 13, 14, Pl. xx11) 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 larvze 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 experi- ments 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 iJlustrate this fact: (1) The adult female in this case has the characters of No. 15, Table I. The antennular or aural spine is nearly three-fourths the length of the first antennular segment. The aural spine has a correspond- ing length in the larve 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 setz on the dactyle. In the first larva the fingers of the small chela also end in prongs, and there is a tuft of rudimentary setze on the dac- tyle. In the adult the carpus of the small cheliped is relatively very long. In the first larva the carpus of this appendage is about one-third the length of the propodus (relatively a little shorter than in the adult). Fig.11, Pl. xx11, may be taken to represent the mother (rostrum here wantirg), and Fig.17 the young. The small chela of the mother is shown in Fig. 2, Pl. xxiv, that of the young in Fig. 15, Pl. xxu1. Another case exactly like 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) (Pl. Iv, Figs. 1,2). The larvee are shown in Pl. xx1, Figs. 1, 2,3,8. The aural spine, at first short, is nearly as long as the first antennular segment when the larva is a week old (Fig. 10, Pl. xxm). In 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, PJ. xx11). 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 heredity. The females with ova are easily obtained; the young are readily hatched and kept 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 definite lines, as, for instance, the relative lengths of the antennular 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 different 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 oceurrence 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. ; 5 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 ~ We i ie OS. ek? >. aie ra aes : >, 2 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 389 it. Has natural selection, then, acted so far as to differentiate the species in more than one direc- tion? There are some facts which favor the view that it has done so, but before the question can be definitely settled we must determine more precisely how far intermediate or aberrant forms represent phases of the 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. I. STRUCTURE OF THE LARVA. (Pl. XLIX, Fig. 174. Pl. rim, Fig. 196. Pls. Lrv-Lvt1t.) These studies in the embryology of Alpheus begin with the growth of the ovarian egg and the early phases of segmentation and extend to the larval and adult periods. In order that the prog- ress of development may be followed in the light of the structure which the embryo finally attains, we will start with a general survey of the anatomy of the first larva of Alpheus sauleyi. A fuller description of the histology and histogenesis of the tissues will be given in the parts which treat of the different organs in detail. A profile view of the larva as if appears while still inelosed by the eggshell and of one imme- diately after hatching is seen in Pl. xx1, Figs. 1 and 5, and the brief and insignificant metamor- phosis which is required to provide it with the adult characters are illustrated and described in a separate paper (Pls. XXI-XXTv). Most noteworthy are the large, stalked, compound eyes, the segmented abdomen provided with its full number of appendages, the short, stumpy antenne, and the swollen chele or pincers of the first pair of thoracic legs. At this stage this Alpheus is a larva, but in a restricted sense, since many adult characteristics are present. It is a larva, with preparations for immediately assuming the adult state. Some of the larval peculiarities are the spatulate telson, the biramous or schizopodal pereiopods (first to fourth pair, inclusive), the radimentary pleopods, the unabsorbed foed 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. 196 (Pl. Lim) the plane of section is nearly vertical and median throughout, except for the posterior halfof the abdomen. The supra-cesophageal ganglion, which is usually spoken ofas “the brain” (8.0. g.),is a complex organ, composed of internal, medullary masses( punktsubstanz balls), and cellular tissue which completely invests them. It is made up of the fused ganglia of at least two segments, those of the first and second antennz. 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 comparison of the series of transverse sections (Pls. Liv, LV, Figs. 211-219) with those made in a horizontal plane (PI. Lyi, 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 Punktsubstanz and later by Dietl (1876) as Marksubstanz. As Krieger remarks, the latter name is bad, since it confuses this tissue with the spinal marrow of vertebrates, with whieh it has nothing to do. It is essentially a /elt of very fine fibers. We will therefore speak of it as the Punktsubstanz, or, to use a more descriptive term, the fibrous substance of the ganglia. The first pair of these, the anterior or optic fibrous masses (Pl. LV, Figs. 212-215), are the largest. They are completely fused on the middle line and form a single compact mass, which is slightly constricted laterally (Pl. Lym, Fig. 242, of.) and which is divided in front (Pl. Lry, Figs. 210, 211), where it gives off two diverging stems of fibrous tissue (sometimes called optic nerves) to the optic ganglia in the stalks of the compound eyes (see also Pl. Lvu, Fig. 240 of.). 390 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Next in point of size are a pair of large lateral balls, which appear kidney-shaped in transverse section (Pl. Lv, Fig. 216,1.f.). Hach is virtually segmented at the lower surface into two lobes (Pl. Lvu, Fig. 242, l. f.). These lobes are closely united to each other, and by a pedicel or stalk of fibers to the lower posterior extremity of the anterior, optic mass. A third pair of fibrous masses (Pl. Lv, Figs. 215, 216, af.) fuse with the anterior mass at the same point. Each of these balls is also bilobed, and from them issue the fibers of the antennular nerves. (Pl. Lyn, Fig. 243, n. au., also Pl. LV, Figs. 212-214, a. 0., nau.) The nerve of the first pair of antennz consists of cells and fibers, which pass to a mass of deeply staining cells (a. 0.), the ear, and to the tissues of the antennular stalk. The fourth pair of fibrous masses (Pl. Ly, Figs. 217, 218, gf., also Pl. Lv, Fig. 243) are intimately associated with the last and with the common bridge of tissue (Pl. 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, fo.) the commissures which surround the esophagus and unite the brain to the ventral nerve cord also originate (Fig. 220). These commissural bands meet immediately behind and below the esophagus, where they fuse (Pl. Ly, Figs. 222, oem.) 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 nerve fibers unite the successive ganglia, which form a doubie chain. These relations are well shown in Fig. 196 and by the horizontal section (Pl. Lv, 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 esophageal ganglion (ganglia of mandibles, first and second mavxillz, 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 (Iig. 196, g. 15-20; see also the series of trans- verse sections, Pls. 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 antennular and antennal nerves already mentioned. The relations and course of the fibers, which are very complicated, are partially indicated.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. LI, Fig. 198, gf). The optic stalks or lobes, bearing the compound eyes (Pl. Liv, Figs. 209, 210, and Pl. Lvu, Figs. 239-242), consist.of 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. Lin, Fig. 197; Pl. Liv, Figs. 209, 210, oc.) 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. The alimentary tract of the larva is a somewhat complicated structure, and the relations of its parts are best understood by reference to sections taken in more than one plane. We can recognize five well-defined portions: the esophagus, the masticatory stomach, the midgut, the hindgut or intestine, and the appendages of the midgut. These are shown in a semidiagrammatic way in the cut (Fig. 2), and the longitudinal section (PI. Lin, Fig. 196) and series of transverse and horizontal sections (Pls. LV—LV11) illustrate the structures in more detail. ° It is interesting at this point to compare the larva shown in Fig. 196 with the longitudinal section of an advanced embryo (Pl. XxLvul, Fig. 168). In both we recognize the foregut, a tube bent on itself, consisting of the esophagus and masticatory stomach (m.s.). In the embryo the latter is closed on the side of the food yolk. In both we also see a vertically directed fold of endoderm (/,, overlying mg® in Fig. 196) 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 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 391 with endodermal epithelium near the point where it communicates with the cavity of the gut. This in the larva corresponds to the midgut (Fig. 196, mg.) and its diverticula. The w@sophagus (Figs. 196, 218-220) is a straight, vertical tube, with very thick walls, which are thrown into longitudinal folds. There is an anterior and posterior fold and two lateral ones, which give to the lumen of the @sophagus the shape of the letter X when seen in transverse section (Pl. Lv, Figs. 241, 242). The walls of the masticatory stomach resemble those of the csophagus, and the folds of the latter are continuous with the valvular stractures of this region. The lateral and median thickenings (Pl. LV, Fig. 221, p. v.) at the point where this portion of the stomach passes into the midgut may be regarded as a rudimentary pyloric valve. The pouches formed between the median ventral fold (Fig. 221) and the lateral folds (p. v.) correspond to the gastrolith sacs in the crayfish embryo (54), but no gastroliths are found in Alpheus. The midgut appears in the longitudinal section (ig. 196, mg.) as a short, restricted cavity. It is, however, a spacious chamber, as we see by examining a series of sections made in other planes (Pls. LV-Lvu). It consists of seven parts or divisions: a dorsal, unpaired, median division (mg. in all the figures), and, opening from this, a pairof anterior lobes (mg.'), a pair of posterior (mg.") and a pair of ventral lobes (mg.”). All these parts are lined with a peculiar columnar epithelium, composed of endoderm 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 appears in the region where the hind gut communicates with the yolk. On the other hand, the demarcation between the wall of the masticatory stomach (of ectodermal origin) and that of the midgut (Fig. 196) is most pronounced. Correlated with this distinction is the fact that the foregut is a blind sac and completely cut oft from communication with the yolk until very late in embryonic life (PI. xiv, Fig. 168). The anterior lobes contain the remnant of unabsorbed yolk (Figs. 218, 237, y.), and in cases where the lining epitheliam is unformed, the food yolk is in contact with the brain. These lobes are sepa- rated by a median vertical partition (mp.), composed of connective tissue and muscle cells, which suspend this portion 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 anterior lobes is incomplete. The dorsal half of it consists of a downward-growing fold of endoderm cells, with a mesodermic core. The ventral and lateral walls of these diverticula are devoid of epithelium, so that the endoderm 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 Pl wt, Fig. 185, mg.*). They lie to one side of and below the hindgut (Pl. Lv1, Figs. 226-230, mg’., 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 in 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 off by the growth of a fold from the side next to the hindgut, downwards and outwards, to form a secondary lobule (gg.2). 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 best shown in a horizontal section (Figs. 236-238). It seems quite probable that a part of the epithelial 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 and 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 the anatomy of the 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 consist of three pairs of lobes or execa. One pair, corresponding to the posterior division of the midgut (Fig. 226, ng."), is imperfectly divided into three 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 OF SCIENCES. pairs pass forward on either side of the masticatory stomach to a point about on a level with the first maxillary segment. The ventral is the larger and longer 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 no food yolk. The gastric ceca are all filled with a coagulable fluid which stains feebly in carmine. The gastric epithelium for a short distance behind the 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, The walls of the blood vessels are exceedingly delicate, so that it is not easy to ascertain their distribution by means of sections alone. The heart (P]. Lu, Fig, 196, H.) is a short tubular chainber, flattened between the dorsal body wall and the enlarged section of the hind gut. It is suspended in the pericardial sinus (p. s.) to the body wall and surrounding organs by means of strands of connective tissue (alz-cordis). The walls of the heart are quite thin, and its cavity is partially divided into three compartments by the growth downward from its roof of two sheets of mesoderm cells (Pl. Lv1, Fig. 231, and Pl. 11, 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, 232, 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 13, to the left of pr.) 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 ophthalmic artery (Figs. 196, 215-229, op, a. op.), which runs for- ward to the region of the eyes and brain. It is not an ophthalmic artery, strictly speaking, but from the first, supplies arterial blood to the brain and anterior cephalic region generally. In Figs. 215, 216, 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 atthe surface of the egg passing forward on either side of the middle line toward the eye stalks, which possibly 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 filled 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 appetdages (Iigs. 193, 230-233, br >°). 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 appears to differ but little from the adulf. The flexor and extensor muscles of the abdomen are most prominent (Fig. 196, mu. f., mu. e.). The former consists of a double rope of fibers, fuse 1 completely together aud very much twisted. They extend from the sides of the thorax to the terminal 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 adductors of the mandibles and great chele. The former consists of a large band of fibers which pass from one side of the body to the other directly + a> MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 393 over the nérvous system (Fig. 221, ad. m.). Closely associated with it are the muscles of the maxille. The large flat tendon to which the adductor muscle of the forceps is attached, is well developed at the time of hatching. Itis formed by the infolding of a sheet of ectoderm cells at the point of articulation of the fingers of the claws, and in a plane at right angles to their plane of action. The outer ends ofthe cells of this infolded sheet now oppose each other and secrete the chitinous tendon, while to their morphologically inner ends the muscle fibers are attached. The connective tissues invest the organs and 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 mesoblast at these points. The green gland (PI. Lim, Fig. 198, ag.) 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 midgut, and of a solid, disc, shaped body. The walls of the tube are 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 body. 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 esophagus and passes down to the labrum and into the eyestalks. The solid almond shaped 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 of the gland is due. The reproductive organs, or what I regard as such, are difficult to find, owing to their very rudimentary condition. They consist of a small cluster of large cells on either side of the middle line between the digestive tract and the anterior end of the heart (Stage x, Fig. 173, R. O.). With this sketch of the structure of the larva we are ready to trace the histery of develop- ment from the earliest stages and to ascertain the manifold changes through which the unicellular egg with its great store of yolk passes, before it attains to the wonderful complexity of the larval and adult forms. Il.—THE ORIGIN OF OVARIAN EGGS IN ALPHEUS, HOMARUS, AND PALINURUS. (a) Alpheus.—The ovaries of Alpheus are paired cylindrical bodies which extend between che 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 (A. saulcyi) they are extremely conspicuous, giving to the female an intense green or yellow hue, according to the color of the egg (Pl. Iv). The oviducts open in the usual way by means of a slit-like valve on the basal joint of the third pereiopods. In Pl. 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 abdominal appendages had been laid. The ovarian ova are ripe by 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. Thus there is a constant snecession of young, and females are not commonly found without either attached or large ovarian eggs. The breeding season of this species extends, as we have seen, throughout the entire year. The structure of the ovary is quite simple (Fig. 11). It is essentially a sac lined with ger- minalepithelium. The external layer of the sac (O. W.) is muscular and contains numerous nuclei. Between the epitheliam and fibrous coat there is a wide space filled with blood. This may be unnaturally Jarge in the preparation owing to the disturbing effects of the reagents employed, _ but it is not wholly 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 polynuclear mass of protoplasm from which the ova are developed, but the eggs appear to originate directly from epithelial cells. The new eggs begin to develop, 394 MEMOIRS Of THE NATIONAL: ACADEMY OF SCIENCES. while the ovarian lobe is yet crowded with ripe ova ready to be laid, on the ovarian wall next 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. Hach 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 & 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') 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 zoéal stage, and the egg contains more than nine times as much yolk as the egg of Alpheus minus, in which the first larva is a zoéalike form, The materials for the yolk must be derived 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 reéntrant blood sinuses which penetrate all parts of the ovarian stroma, as in the lobster (Homarus) 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. 11, G. V.) is filled with coarse chromatin grains, and in the early phases grows relatively faster than the rest of theegg. In the egg, (e,' to the left) which is z3,5 inch in diameter, the diameter of the germinal vesicle is one-half that of the entireegg. 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 nucleoli. The older eggs are spherical; their food yolk is often vacuolated, as in later stages, and they are invested by a single membrane, 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 next 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 fased and always vacuolated in preparations which have been subjected to alcohol and turpentine. In the ripe egg the nucleus was not seen, but it is quite probable that careful sectioning would show 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 Homarus. (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 olive 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 syneytium and consists of a matrix in which great numbers of small nuclei are embedded. These nuclei, with surrounding protoplasm, 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 Pl. xxv, Figs. 3, 6. Vig. 6 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 germogens, the centers of dispersion 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 indifferent nuclei of the ovarian stroma to the large peripheral ova. The ovary is supplied with blood by means of sinuses which penetrate to all its parts (BI. 8.). The sinuses are definite reéntrant channels with thin membranous walls. The ovarian tissue (Ct. 8.) 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, 0”) swells out, becomes spherical, and its chromatin has the charac- hal rs, ~~ XN -* _ a * . Fr. ioe ie |, to , wre a - ig | MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 395. teristic granular appearance of the germinal vesicle of the young egg. The first trace of the yolk (O%, O*, O°) appears in the outer granular layer which surrounds the germinal vesicle. This layer represents primarily the cell protoplasm, in which the yolk is formed. The cell takes on a definite shape and is very early invested with a follicular coat (I. C.). In an egg a little older (O*) the nucleolus has appeared, and in still older eggs (Fig. 6, O, O') a delicate chorion (Ch.) can be seen. This is secreted by the cells of the follicular envelope (I. C.). The growing eggs pass out from the central to the peripheral parts of the lobe iv the sheets of stroma between the blood sinuses. Distinct yolk spherules are very early seen (O°) and are of uniform size, but in maturer eggs (Fig. 6, O, O') the germinal vesicle is sometimes surrounded by a central layer of small spherules and a peripheral layer of larger ones. The germinal vesicle is centrally situated and always contains a single excentric nucleolus, besides stellate masses in the chromatin reticulum.* (c) The Spiny Lobster (Palinurus).—In the spiny or rock lobster from the Bahamas the ova originate exactly as in Homarus, and the structure of the ovary is essentially the same. There are several nucleoli, as in Alpheus. The ovary is not nearly so richly supplied with blood sinuses as in the cases just considered. This is perhaps correlated with the fact that the amount of yolk and the subjoined notes are largely extracted from a preliminary notice on ‘The Reproductive Organs and Early Stages of Development of the American Lobster.” (23.) The structure of the mature ovary is somewhat peculiar. The free, unextruded eggs fill the lamen of the ovarian lobes. The lobe or tube itself consists of the proper ovarian tissue and the outer muscular wall, which is very thick. The stroma is characterized by the presence of gland-like structures, blood sinuses, and immatnre ova. The glands are in close relation with the growing eggs. They are plaited or folded structures, and consist 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 function 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 ceca have much thicker walls; the rapidly dividing cells are suialler, 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 cecum resem- bles a narrow bag with an egg pushed into its mouth. The glandular cells are directly continuous with those of the follicle. The axial portion of this ovarian lobe is composed of hollow spaces, blood sinuses, and loose stroma, int which very young eggs occur. Degenerating cells occur not only in the stroma, but probably in the developing ova also. In Peripatus Nove Zealandiaw the yolk is described by Lilian Sheldon as arising not only from the egg proto- plasm, but also from the follicle cells (57), When ten to fifteen days have clapsed after egg-laying (eggs in egg-nauplius stage), the gland-like bodies have almost wholly disappeared. The walls of the cxca are shrunken and crumpled, and the latter have been crowded to the extreme periphery of the ovary. The ovary now contains a solid core of immature 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 bands. At a still later period (eggs with eye pigment, four to five weeks’ old) the glands are present merely as shriveled remnants. Later still (lobster taken August 21; egg embryos in a late stage’) there is no trace of gland-like structures. In the ovary of a lobster (taken June 30), with eggs about to hatch, the condition is similar to the last. It is now abont eleven months since the eggs were laid, yet the diameter of the largest ovarian ova is only about one- half that of the 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 bave been described as probable yolk glands are present in the peripheral parts of the ovaries only during the limited period of from two to three weeks after the eggs are laid, and when the org ins are recovering from the changes which follow this event. Their structure is quite unlike that of bloodvessels or sinuses with which they are intricately associated, and their relation to the growing eggs seems to imply that they have some function to perform in the nourishment of the peripheral ova. Their short existence, on the other hand, might lead us to suspect that they were more or less rudimentary structures, or that they were concerned with the secretion of the gluey substance with which the eggs are coated at the time they are laid. Their true function, however, remains to be determined. Ovaries which I have examined, taken in summer (July) from lobsters ( ‘‘ paper shells”) which have receutly moulted and which do not carry eggs, present very thin walls, and the largest ovum measures in diameter about one- half that of the mature egg. These lobsters have probably hatched a brood the present season and have afterwards moulted. (Compare the ovary of the lobster taken June 30 above.) Some allowance is to be made for individual difference, but the slow growth of the ovarian ege, which we have traced from the snmmer when eggs were laid to the 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 each egg is very small, although the number of eggs produced by this animal is enormous. At Nassau, Palinurus begins to spawn in June. (da) Comparison.—Ishikawa describes very fully the ovaries and ovigenesis of the prawn At- yephyra compressa and concludes that the ovum “originates from the infer 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 chorion it secreted gradually during the growth of the egg by the cells of the egg follicle. The large glandular cells found in the oviduets of Atyephyra possibly secrete the viscid fluid by which the eggs are attached to the swimmerets, yet this point needs comfir- mation. The chorion was found in the ovarian egg of Pagurus by Mayer (39), who says: Das Eierstocksei von Pagurus ist in der ersten Zeit seines Bestehens eine echte Zelle mit Protoplasma, Kern und Kern-Kérperchen. Spiiter findet eine Einlagerung yon Deutoplasma und die Bildung einer Hiille aus Chitin statt. Endlich wird der Kern unsichtbar; das Ei stellt dann eine Cytode vor. Das fertige 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 fluviatilis) 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. 7 In Cranyon vulgaris Kingsley (31) finds that the late ovarian ova resemble the newly laid eggs. There is a thin structureless envelope (chorion), but no trace of an inner vitelline membrane. Ludwig’s general statement that the egg cells of all 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 protoplasm 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 Beneden, 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 category of secondary structures would fall also those secreted by special 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 separation 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 ou M. Claparéde I’a si nettement définie dans son travail sur les vers Nématodes: C’est la couche externe du protoplasma de Vuf, qui, ayant acquis une densité plus grande que la masse sous-jacente, se sépare de celle-ci par un contour net et tranché. Elle est A ’@euf ce que la membrane cellu- laire est 4 la cellule; elle se forme de la méme manieére. 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 (Gammarus locusta) 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 protoplasm 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 iasects it appears that a chorion is always present in ovarian eggs, while, on the other hand, arachnids possess a vitelline membrane and the eggshell is secreted in the oviduct. There is no simple rule to express the appearance of egg membranes in a diversified group like the Arthropods, and, considering that these structures are purely secondary to the cell and expensive products however formed, this is what we should expect. Their function is chiefly pro- tective, and where a chorion is present in the ovary a yolk membrane is not developed, but the latter is present, as in spiders, when the shell is a later product. Erdl (15) describes three egg- membranes for the lobster, but it is clear, as Mayer has already shown, that the inner, delicate membrane which has been described for the decapod egg, is a secretion product of the blastoderm. Ill. SEGMENTATION OF THE EGG OF ALPHEUS 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 spherules of minute and uniform size. The nucleus is central, or nearly so,* and consists of an ill-defined mass of protoplasm, in which a fine chromatin network is suspended. In the next phase (Pl. xxv1, Fig. 14) the nucleus is elongated and about to divide. Division appears to be direct and irregular. At a somewhat later stage the phenomena of the most interest occur (Figs. 12,13). Each product of the first nucleus has developed a swarm of nuclear bodies (S.8.), 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 tendency 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. In one case there were two large segments, which nearly divided the egg in two, besides several smaller ones. Nuclear matter consists either of small particles or of indefi- nite reticulated masses, resembling the first nucleus (Fig. 14). Clear areas are sometimes found. with nuclei which appear to be breaking down. About eight nuclear swarms or clusters are present in the stage shown in Figs. 12,13. The nuclei vary in size from refringent particles to bodies of ordinary nuclear appearance. Figs. 25 and 26 represent two sections of one of the clear areas in the same egg from which Fig. 12 was drawn. This clear field has several degenerating nuclei near its border. The largest one (S. C.) is included in both sections. A small chromatin mass with indistinct body lies next it (S. C.?), and other similar bodies occur in different sections. The cell S. C. contains two chro- matin balls, and in Fig. 26 (the next section but one in the series) this body appears to be dis- charging through its broken-down wall numerous minute elements (8.) 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 and 23 are also from the same egg. Here we see structures similar to the ceil just mentioned. They are surrounded by yolk and consist of a deli- cate reticulum in which usually one large nucleolus is suspended, besides great numbers of small chromatin particles. Various stages of growth are here represented, and 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- mal, and I conclude that we rather have in this species a remarkable modification of the usual indirect cell division, attended by an equally remarkable degeneration of nuclear material. In the last stage obtained (Fig. 29) the whole egg is filled 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 vr of A. sauleyi, 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 reference to these cells. This case is interesting when we compare it with the degeneration of cells to be deseribed in another section, and from a cytological point of view it deserves careful study. “In single sections the nucleus is strictly central, but whether it is so with respect to the entire egg it is not easy to determine. Minot states that the egg nucleus is always eccentric.—Am. Naturalist, Vol. xxu1, 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 Alpheus heterochelis of the Southern States, to a Bahaman form which hatches as a zoéa but which otherwise resembles this species very closely, and to Alpheus sauleyi, 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. sauleyi) 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 Pl. xxvu, Fig. 17. I regard the nucleus of this egg as the female pronucleus. It consists of clear protoplasm, which stains feebly and sends out processes on all sides into the yolk, and of an indefinite chromatin network suspended in it. The massive yolk is composed of corpuscles of uniform size, excepting at the periphery where they are much smaller. Numerous small Jacunz occur, representing parts 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 ; itis lenticular in shape, and granular in appearance, and is surrounded by protoplasm which spreads into the yolk. The once 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 nucleus 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 spberules 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 parts of the yolk (Fig. 10) around the nuclei, thus giving rise to sixteen blastomeres or partial yolk pyramids. 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 whieh 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 nucieus. The blastoderm or primitive ege 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 plates or cells, the nuclei and surrounding protoplasm of which lie at the surface. The fifth segmentation phase is shown in Figs. 15 and 51. 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. e 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. 4, Y. P.) agree with those in Alpheus and are probably formed in a similar way. In Pale- monetes vulgaris the history of segmentation appears to be essentially the same. The nucleus and base of one of the yolk pyramids of this form is shown in Fig. 24. Here we see that the peri- nuclear protoplasm has a rayed appearance, being produced in all directions into very delicate threads which ramify among the yolk spherules. Some of these threads moreover unite with 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. MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 415 The two divisions of the foregut, @sophagus, and masticatory stomach, have the relations already described. The wall consists of a single layer of tall columnar cells. In the masticatory division the wall has begun to thicken next the yolk screen, its cells being cuneiform, and the nuclei élongated and crowded below the surface. From the anterior wall, muscle or connective tissue cells extend forward under the brain. POM mg! Fic. 1.—Diagrams of transverse sections through the alimentary tract of an embryo of Alpheus saulcyi which is nearly ready to hatch, to show the origin of the gastric gland from the posterolateral lobes of the midgut. Section Lents the hindgut and lobes of the “liver,” Section 11 the hindgut where it merges into the meseuteron. gg', gg’, Secondary lobules of mg!; HG, hindgut; mg', postero-lateral lobes of midgut. HG HG HG Il The development of the mesenteron can be understood by reference to Figs. 162-165, 168, and 185. The endodermal epithelium spreads by the division of its own cells and by accession of cells from the yolk, both forward over the nervous system and upward against the sides of the body. This is shown in the series of horizontal sections (Fig. 162-165). Fig. 168 which is from an embryo a little more advanced, shows that the endoderm is rising from the nervous cord near its point of flexure, into a transverse vertical fold. Simultaneously with the upward growth of this ventral fold, two dorsal longitudinal folds grow downward, and\finally unite with the ventral fold and with each other, thus constricting off from the alimentary tract two lateral pouches, the pri- mary lobes of the “liver.” The folds grow forward and the constriction proceeds 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 essentially the same as in the previous stage. The cells are prismatic, and the nucleus spherical, and, as in all stages, filled with numerous nucleoli or chromatin balls. The cell walls are very delicate and the protoplasm often contains large vacuoles. / i 1 2 i } . 99 dy ang? mo, FS. Fic. 2.—Semidiagrammatic representation of the alimentary tract and its appendages in the first larva of Alpheus saulcyi. The middle line of the body is also shown. FS, foregut ; gg 1-3, secondary lobules of postero-lateral lobe of midgut; HS, hindgut; mg, midgut; mg 1-3, an- terior, lateral, and postero-lateral divisions of midgut; mo, mouth. _/— 7 1S Cee ean med el ores 416 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Wandering cells still occur in all parts of the yolk, though 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 epiblast is conspicuous in Fig. 168 just in front of the optic lobes. This corresponds in-position with the dorsal plate (Fig. 153 dp.), and is probably 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. 168,) 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. Auteriorly 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 antennary 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. 166-169, B. 8.) 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 168 (#.), and is essentially the same as in Stage 1x In Fig. 173 there is a small solid cluster of peculiar cells (R. O.) 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 differentiated 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 rx (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 parts of the body (Figs. 168, 171, 172, mw., mu. f., mu. €., g. m. a.), but most striking at this stage are the great flexor and extensor miele of the abdomen. The green gland (Fig. 170, A. G.) is another organ which we now meet with foe the first time. It is an irregular 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 find 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 XJ.—EMBRYO OF ALPHEUS HETEROCHELIS NEARLY READY TO HATOH. The later stages (Stages vI-x) have had reference to a single species of Alpheus, namely, Alpheus saulcyi, the larva of which is described in the first section. The embryo of Alpheus heterochelis 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 convénient connecting link between the larva described in Section I and the last stage. The embryo of Alpheus heterochelis is represented by a longitudinal vertical section and by a series of transverse ones (Pls. L, LI). The ~ longitudinal sections of Stage x, of this stage, and of the larva (Figs. 168, 180, 196), 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 1s 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 sereened from the yolk by a membrane composed of large cells, which extend backward over the nerve cord. A double band of muscles (Figs. 168, 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. t MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 417 The mesenteron (mg.) is very largely reduced in size and is filled with a granular coagulum, and, anteriorly next the head, with vesiculated and eroded remnants of yolk. The endoderm lines all but the anterior third of this cavity, extending farther forward on the dorsal wall. A few wandering cells are still presentin the peripheral parts of the cavity next the advancing edge of the endoderm. Those elements, represented in Fig. 182, prove to be endoderm cells mechanically detached from the wall of the mesenteron. The primary lobes of the midgut (“liver”) are larger but otherwise similar to those described in Stage x. The endoderm cells are greatly vesiculated, and the cell protoplasm has often a striated appearance. The heart (Figs. 180, 186, H.) has undergone very considerable changes since the period repre- sented by Figs. 164, 168. It is no longer dorso-veutrally 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. Its suspension in the pericardium is very delicate. The ectoderm cells send down spindle-shaped processes (Fig. 186), the Hcetoderm pfeiler of Reichenbach, and to these, meso- dermal elements become attached. The cavity of the heart is imperfectly divided by lateral partitions into three longitudinal compartments. In Fig. 186 the partitions 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 XIJ.—THE FIRST LARVA. We now reach the stage with which this paper began, the first larva of Alpheus saulcyi. The histological structure of the zoéa in the species with a regular metamorphosis differs dnly in minor particulars from the larva already described. The organs are all very much smaller, and the cells are relatively larger and less compact. The mesenteron is about half filled with the unaltered and unabsorbed food yolk. Wandering cells are almost entirely absent, and the endo- 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. Stace XIJI1—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 (Pl. Lut, Fig. 195.). These have now acquired the folds or plates for increasing the respiratory surface, and are more efficient 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 optic ganglia and anterior parts of the brain are drawn closer together. Ina larva four days old (Pl. xx1, 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 after the time of hatching. The structure of an Alpheus 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 fori. 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 differentiation 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 —_— characteristic is certainly not so apparent in Alpheus, yet I believe that in this form it is present in some stages, though in a less marked degree. Astacus (?)—I have studied several critical stages in the development of the crayfish, critical at least so far as the appearance of degenerative products is concerned, with an eye to comparison with Alpheus and Homarus.* The youngest set of embryos Coreen tiaa nearly to Reichenbach’s stage E, but differs from it in some details. Rudiments of five pairs of appendages are present, the two maxillw 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 antenne. The bodies which Reichenbach ealls ‘“‘secondary mesoderm” oceur in ainndatieet in or near the wall of the endoderm sae next the embryo. They also abound in the yolk under the ectoderm, and are most numerous in the area extending from the optic invaginations to the mouth or slightly bebind it. In thig 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. vii, 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 in 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 comntand, 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 outiines of vesicular bodies which exhibit but slight reaction to the stain. These I regard as degenerated cells. Z The next stage of Astacus which I have studied corresponds nearly to Reichenbach’s stage G. Right pairs of appendages are present, and there are rudiments of a ninth pair. The first and second maxille appear as distinct buds, while the third pair of maxillipeds is represented by a proliferating cell area only. 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 gndodermal 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 radjal 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. 18, a, b, ¢, or k, k,' Fig. 20), containing a single chromatin ball or several balls, occur not only in the yolk underneath the ectoderm and in the vicinity of the endodermal nuclei, but also in the central yolk of the endoderm sac, 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 studying the crayfish development af this time I am indebted to the kindness of my friend, Dr. William Patten, who sent me a number of important stages collected at Milwaukee. *. hat athe Nis vig [Ja ee _ > re wits oad \ ¥ MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 429 Reichenbach thus summarizes his observations on the “‘ sekundiire Mesodermzellen :” Die fraglichen Elemente sind als Zellen zu deuten, deren Kerne nicht immer die Beschaffenheit gewohonlicher Zelikerne haben, dieselbe aber friiher oder spiiter erlangen (Fig. 20, m, m?, Platexxvit). Sie nelmen ihren Ursprang innerhalb derjenigen Entodermzellen, welche die ventrale Wand des Urdarmsiickchebs zusammensetzen durch eine niiher zu erforschende Art endogener Zellbidung, bei welcher die in der Mehrzahl in den Elementen des Entoderms vorhandenen Kerne eine wichtige Rolle zu spielen scheinen. In den dem Stadium D vorangehenden Entwicklung- sperioden hat jede Entodermzelle meist nur einen Kern; dies trifft auch noch zum Theil fiir Stadium D zu. Bald ver- mehren sich aber die Entodermkerne ganz erheblich und endlich beginnen die sekundiiren Mesodermzellen aufzutreten. Wenn eine gréssere Zahl der sekundiiren Mesodermzellen in den Entodermelementen liegen, so scheint das Kernma- terial verbraucht zu sein. Es wandern nun aller Wahrscheinlichkeit nach diese Zellen, deren Kerne anscheinend noch in der Metamorphose sich befinden, aus dem Entoderm aus und begeben sich unter die Embryonalanlage. Die ketreffenden Contouren des Entoderms lassen oft noch Spuren dieser Wanderung erkennen. Ob sie wirklich aktiv auswandern oder auch ausgestossen werden, ist nicht festzustellen gewesen. Sie begeben sich nun unter die iibrigen Mesodermzellen und sind bald nicht mehr von ihnen zu unterscheiden. Aus diesem Grund fiihrte ich fiir sie den Namen ‘‘sekundiire Mesodermzellen” ein, wiihrend die ilteren Urmesodermzellen als primiire bezeichnet werden. Da die letzteren die Tendenz zeigen, za kompakteren Massen zu verwachsen, so darf man wohl vermuten, dass die sekundiiren Mesodermzellen die Blutzellen liefern werden (54, p. 36). It is interesting to notice that in Alpheus, Astacus, and Homarus degenerating cells appear in greatest force at about the egg-nauplius stage, and from that time on their numbers begin to wane. In Astacus, Reichenbach first noticed the “‘ sekundare Mesodermzellen” in stage D (that is, when the optic disks, the thoracic-abdominal plate, and the mandibles are outlined), which nearly corresponds to Stage Iv of Alpheus. In stage D the bodies in question are most abundant under the optie disks (Kopflappen) and in the region of the upper lip, but become more generally dis- tributed in the egg-nauplius. _ According to Reichenbach, “ gastrulation” 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.” He says of the latter: Sie bestehen aus protoplasmatischer, feinkérniger Substanz und enthalten vacuolenartige Einschliisse, die ilnen ein schaumiges Aussehen geben; ich habe sie als weisse Dotterelemente bezeichnet. Sie liegen entweder dicht unter dem Blastoderm oder im Centrum des kugligen Eies und verschwinden sehr bald (Op. cit., p. 7). According to my view these bodies correspond to the vesiculated elements (m, Fig. 20), and both represent cells in process of dissolution. If Figs. 18 and 20 are compared (the latter being a copy of Reichenbach’s Fig. 67) we will find a striking correspondence between these peculiar cell products in both Astacus and Alpheus, a correspondence which is even more marked when the comparison is made with the lobster. Reichenbach emphasizes the statement that naked balls of nuclear material never occur free in the yolk outside the endodermal sae. 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 Alpheus. My 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 appearance at nearly similar times and play a similar réle. They are derived from all three layers of the germ, and in Alpheus 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 and function as nutrition. That any play a formative réle, giving rise to blood cells for instance, as Reichenbach supposes, there is no direct evidence. The vitellophagous func- ’ tion seems to be in abeyance in Alpheus, but in all cases the yolk is comminuted and chemically changed in the neighborhood of these bodies. Nusbaum (45), following Morin, believes that 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 ameeboid, endodermal cells. This is reversing the account, and, in so far as the origin of the “see- ondary mesoderm” is concerned, it is not supported, so far as [ am aware, by a single observation. ‘’ SE nee ee AVE a ee we eo. . fe ee * rie bs 430 MEMOIRS OF THE NATIONAL ACADEMY CF SCIENCES. Ishikawa (27) finds in Atyephyra after the close of the invagination stage, certain proto- plasmic elements under the ectoblast, which he thinks may correspond with the ‘ white yolk ele- ments” just referred to, and he also identifies’‘‘ secondary mesoderm cells,” but does not trace their origin or function. * They are “ small granules,” easily stained by logwood solution, and some are of considerable size and have a clear cell Satine: “hese are mostly aggregated in the cephalic region between the involutions of the ectoderm cells, but are also found in all places.” In time of appearance and in their position, he says they seem to correspond to the “ secondary meso- derm cells” of Astacus. This short notice with his figures leaves little doubt that these bodies are similar to those just described in 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, Pl. xi), and Lebedinski (34) has deseribed ‘secondary mesoderm” in the embryo of the Mediterranean sea crab, Hriphia spinifrons. According to this observer they are found in all stages from the “ gastrala” on, to the egg-nauplius; they are derived from ectoderm, and probably give rise to blood cells. In the stage with one pair of maxillipeds these elements are in active proliferation : Man findet, die Zellen desselben bieten verschiedene Momente und Zustiinde des Zerfallens dar; dieses Zerfallen der Zellen steht in genauen Zusammenhinge mit der Entstehung der Blutkérper. He further says: Ueber die Bildung des Blutes kann ich nichts bestimmtes mittheilen. Im Stadium des ersten Paars kieferfusschen sind die ersten Blutkérperchen vorhanden, welche zum ersten Mal im Bereiche des Herzens vorkommen, wo sich auch am friihesten das sekundiire Mesoderm riickzubilden beginnt. From these quotations it appears that the “secondary mesoderm” shows sigus of degenera- tion, and its conversion into blood cells is an unverified inference. It seems more probable that the structures in question correspond with similar bodies already noticed in Alpheus, Homarus, and other Decapods, and that in all cases they have to do primarily with the dissolution and not with the construction of cells. Wheeler (67) in 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 probably also in Astacus. In Doryphora two masses of endoderm are found, one under the stomodum 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: The karyochylema becomes vacuolated, probably with substances absorbed from without, to jndge of the larger size of some of these nuclei, while the chromatin ceases to present the threadlike coil and becomes compacted into irregular masses between the vacuoles. Finally the vacuoles fuse and the masses of chromatin, formally numerous, agglomerate to form one or two large irregular masses which usually apply themselves to the wall of the clearly vesie- ularnucleus * * * 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 in Reichenbach’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 i is similarly disposed around the wall of a vacuole. Bruce (10) figures certain yolk cells undergoing what he considered to be endogenous cell division in an advanced embryo of a spider, and compared it with the endogenous cell division which Reichenbach describes as taking place in the endoderm cells of Astacus. The disintegration which has been attributed to the leucocytes of the mammalian blood affords an interesting comparison with the phenomena which have been described for the Arthropod embryo. Howell’s careful observations (25) support the view that the multinucleated leucocytes — are disintegrating cells. ‘The leucoblasts enter the lymph stream, and eventually reach the blood as unicellular leucocytes.” Here they undergo changes, acquire amceboid movements, while the nuclei elongate, become constricted, and finally fragmented. ‘The multinuclearstage * * * is probably followed by a complete dissolution of the cell.” Howell adopts the highly reasonable :! MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 431 view that the nuclear fragments persist for a while in the circulation as the blood plates, and considers it probable that the latter take some part in forming the paraglobulin of the blood. If the blood plate is then a degenerate body, it may be compared to the spore-like masses of chro- matin, which are discharged from the disrupted cells in the lobster or crayfish embryo. VII.—THE ORIGIN AND HISTORY OF WANDERING CELLS IN ALPHEUS. The wandering cells in Alpheus have a triple origin, from the blastosphere, from the invagina- tion, and from 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 inte the yolk (Pls. XxxuI-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 ceils.” Since these classes can 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-abdominal plate, and the parts of the embryo in front of it as wandering cells. Ihave 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 present paper, they must be understood to refer to the wandering cells which have been defined above. The term “embryonic nuclei” is used for convenience merely to discriminate the remaining nuclei of.the egg from those of the wandering cells. The object immediately in view is to determine the fate of these wandering cells, to ascertain what formative réle they play while the mesoderm, and more particularly the endoderm, are being differentiated into definite cell layers. In the following account, cells which have parted all con- nection with the thoracic-abdominal plate and have entered the yolk are enumerated as wandering cells. In an earlier part of this paper I gave an account of the origin and supposed fate of the wandering cells, the general conclusion being that in the early stages (Stages I1I-v) they pass from 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 equal probability as originating, in some measure at least, in the opposite way, that is, as budding from superficial cells not concerned with the thoracic-abdominal plate, and migrating into the yolk. A careful study of successive stages _ would not support this idea, but the objection could not be satisfactorily answered, and neither view could be readily proved. I therefore-undertook a renewed and wore precise study of the wandering ceils in Alpheus, and I think that their fate has been definitely settled. The number of wandering cells which occur in the yolk, and the number of “ embryonic cells” (that is, all the other cells of the egg) have been enumerated in five different stages, including seven different embryos, from the period of delamination at the close of primary yolk segmentation to the early egg-nauplius condition (Stages 11-v.) This covers the most important period so far as the wandering cells are concerned. ~Lhe rate of increase of both wandering cells and 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 and to the less differentiated regions, while it is understood that all the cells constitute the embryo. 432 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 2 TABLE I.— Showing the number of nuclei in yolk, and the number of other “embryonic nuclei,” and the relative increase and decrease in these bodies from the close of yolk-segmentation to the egg-nauplius period. 3 aa 2S ao Be here been wodified. ; Delamination.—(11) The segmentation has been thoroughly reviewed in Section vy, 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 blastodermie cells delaminate and their 4 products pass into the yolk. In Alpheus sauleyi a similar migration of cells from the superficial to~ ‘ the deeper parts of the egg occurs, but in this case it was not determined whether this migration : was preceded by delamination or not. These cells appear to originate in greatest number over that side of the egg which corresponds in position to the embryonic area. It seems possible that a these cells may represent a primitive endoderm, the function of which has been usurped. In the lobster they speedily degenerate. Invagination Stage—(12) The invagination stage, which soon follows, results ia the admis- sion of more cells into the yolk and in the formation of an organ called in this memoir the ventral _ or thoracic-abdominal plate. Cells also_ continue to pass into the yolk from the ventral plate, While cells are constantly being subtracted from the plate, it is constantly 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 cells, derived originally from three sources: from the blastoderm, from the cells which are first invaginated, and from those which originate later from the ventral plate, after all trace of the superficial pit has disappeared. Germ-layers.—(13) These migrating cells, which are collectively called “the wandering cells” in Section vil, spread to all parts of the egg. While it is perfectly obvious that these bodies represent mesodermice and endodermice tissues, it is not so easy to determine what particuiar cells give rise to this or that layer, nor iS it easy to décide in many cases, from a superficial study, whether migrating cells may not be derived from the ectoderm in various parts of the embryo. This sub- y “The structure of the ovary of the lobster has been recently described by Bumpus in a detailed paper upon the ae ae ee he. embryology of this species. He has called attention to the folded character of the ovarian epithelium, which is so # marked in the young or immature ovary. (The Embryology of the American Lobster, by Hermon Carey Bumpus, Journ. of Morphology, Vol. v, No. 2, 1891.) t Polar bodies have been recently described in the external eggs of the Jobster by Bumpus. Op. cit. 458 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. ject is fully considered in Section vu, the general results being: (1) That it is not possible to decide what part the primary yolk cells play in Alpheus, 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) that those celis which give rise to the endodermal epithelium in the egg nauplius 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 period. The mesoblast has become a well-recognized layer before the endodermal epithelium has appeared. (14) The egg, with centrally moving cells which have budded from the blastoderm, may be compared with the planula stage of Coienterates, and the internal cells may represent the primi- tive endoderm. 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 theinvagination 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 Alpheus and Homarus the primitive mouth arises on a line between the rudiments of the first pair of antenn, but these appendages are never post-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 v1. It is remarkable that the early segmentation stages of Alpheus minor are attended with the degen- eration of protoplasm. 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 differentiation of the germinal layers, and are not confined to any one layer at a later period, but in Alpheus saulcyi they are most characteristic of the wandering cells, which represent mesoderm and endoderm. The “secondary mesoderm cells” and “ white-yolk elements” which have been described by Reichenbach, are to be regarded as degenerating cells. Degenera- ting cells also occur in connection with the ‘“ dorsal plate.” The Eyes.—(18) The details of the structure and development of the eyes and nervous system are fully reviewed in Sections VIl and Ix. The eyes and optic glanglia are derived from the optic disk, in the formation of which there is in Alpheus ho 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 invaginate area of the optic disk of the erayfish. 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 retinogen, which is primitively a single layer of ectodermie cells. (19) I am inelined 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 etfeect on the development of the eye pigment, but in Palemonetes the distal retinular 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. ADELBERL COLLEGE, F « s MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 459 XI.—REFERENOES. 1. 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Animaux articulés 4 Pieds articulés, in Histoire Physique, Politique, et Natwrelle de V'Tle de Cuba, by Ramon de la Sagra. : 19. Heatucote, F»G. The Early Development of Julus terrestris. Studies Morph. Lab’y Univ. Cambridge, Vol. 11, Pt. 1, pp. 219-240, Pls. XXII-XXx11I. 1884. 20. Herrick, F. H. Notes on the Embryology of Alpheus and other Crustacea, and on the Development of the Compound Eye. Johns Hopkins University Circulars, Vol. v1, No. 54, pp. 42-44, Figs. 1-8. 1886. 21. ———. The Development of the Compound Eye of Alpheus. Zool. Anz., No, 303, Figs. 1-5, 1889. 22. ———. The Abbreviated Metamorphosis of Alpheus and its Relation to the Conditions of Life. Johns Hopkins University Circulars, Vol. vu, No. 63, pp. 34-35. 1888. In the same number are Notes on the “ Habits and Color Variations” and on the ‘‘ Development of Alpheus.” 23. ———. The Reproductive Organs and Early Stages of Development of the American Lobster. Johns Hopkins University Circulars, Vol. x, No. 88, pp. 98-101. See also No. 80 of Johns Hopkins University Circulars, 1890, and Zool. Anz., Nos. 361, 362. 1891. 24. Herer, K. Die Embryonalentwicklung von Hydrophilus piceus L. LErster Theil. Jena, 1889, pp. 1-98, Taf. I-XIL. 25. HowreLt, W. H. The Life-History of the formed Elements of the Blood, especially the red blood Corpuscles. Journ. of Morphology, Vol. tv, No. 1, pp. 57-116, Pl. rv. June, 1890. 26. Huxtey, T. H. The Crayfish. Jnt. Sei. Ser., Vol. xxvii. New York, 1880. 27. IsHikawa, CHryoMaTsuU. On the Development of a Fresh-water Macrurous Crustacean, Atyephira compressa, De Haan. Quart. Journ. Micros. Sci., Vol. xxv, New Ser., pp. 391-428, Pls. xxv-xxvur. 1885, 28. Kent, W. SavitLe. Sound-Producing Arthropods. Letter in Nature, Vol. xvu, p. 11. 1877. 29. Kinestey, J. 8. A Synopsis of the North American Species of the Genus Alpheus. Bull. of the U.S. Geol. and Geog. Survey of the Territories, Vol. 1v, No. 1, Art. vit, pp. 189-199. 30. ———. The Development of the Compound Eye of Crangon. Journ. of Morphology, Vol. 1, No. 1, pp. 49-64, Pl. 11. September, 1887. See also Zool. dnz., Jahrg. 1x, No. 234, pp. 597-600, 1886, and Amer. Naturalist, Vol. xx, pp. 862-867. October, 1286. The Development of Crangon Vulgaris. Second paper. Bull. Essex Inst.,Vol. xvi, Nos. 7-9, pp. 99-153, Pls. 1-u. Salem, July, 1886. 6, 31. 460 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. = 32 The Development of Crangon Vulgaris. Third paper. Bull. Essex Inst., Vol. xx1, Nos. 1-3, pp. 1-42, +6 Pls. 1-111. 1889. i 33. Krrecek, K. R. Ueber das Centralnervensystem des Flusskrebses. Zeit. f. wias. Zool., B. xxxii1, pp. 1-70, Taf. XXXI-XXXIII. 1879. a : 34. Lesepinski, J. Einige Untersuchungen tiber die Entwicklungsgeschichte der Seekrabben. iol. Cen’blt., B. x, 60, 61. Nos. 5 and 6, pp. 178-185. 1890. . LEREBOULLET, A. Recherches sur le Mode de Fixation des Gufs aux fausses pattes abdominales dans les Kerevisses. Ann. de Sci. Nat., tv Sér., T. 14, pp. 359-378, 1 Pl. 1860. j3. ———. Recherches d’Embryologie Comparée sur le. Développement du Brochet, de la Perche et de 1’Ecrevisse. Mém. prés. par divers Savants & V Acad, des Sci. de VInst. Impér. de France, T. 17, pp. 447-805, Pls. 1-6. Paris, 1862. = . Locy, W. A. Observations on the Development of Agelena naeyia. Bull. Mus, Comp. Zool., Vol. xii, No. 3, pp. 63-103, Pls. 1-12. 1886. . Lupwiac, H. Ueber die Eibildung im Thierreiche. Arbeit. aus dem zoolog.-zootom, Inst. in Wiirzburg, B. 1, pp, 287-510, Taf. xmi-xv. 1874. . Mayer, Paut. Zur Entwicklungsgeschichte der Dekapoden. Jenaische Zeit. Naturwiss, B. x1, pp. 158-269, Taf. — XUI-xXv. 1877. . Mrrescukowskl, C. von. Eine neue Art von Blastodermbildung bei den Dekapoden. Zool. Anz., No. 101, pp. 21-23, Figs. 1-8, v Jahrg. 1882. : . MorGan, T. H. A Contribution to the Embryology and Phylogeny of the Pyenogonids. Studies from Biol. Lab’y of the Johns Hopkins University, pp. 1-76, Pls. i-vu1. Baltimore, January, 13891. . Miuier, Fritz. Palewmon Potiuna. Kin Beispeil abgekiirzter Verwandlung. Zool. Anz., No, 52, pp. 152-167. 1850. Berichtigung, die Verwandlung des Paleemon Potiuna betreffend. Zool. Anz., No. 55, p. 233. 1880. . Nuspaum, JosepH. L’Embryologie @Oniscus murarinus. Zool. Anz., No. 228, pp. 455-458. 1886. L’Embryologie de Mysis Charmeleo. Arch. de Zool. Expér. et Génerale, 2d Ser., T. 15, Nos. 1-2, pp. 123-202, Pls. I-x11. 1887. }. Packarp, A. S. Notes on the Early Larval Stages of the Fiddler Crab and of Alpheus. Amer. Naturalist, Vol. XV, pp. 784-759, Figs. 1281. . Parker, G. H. The Histology and Development of the Kye in the Lobster, Bull, Mus. Comp. Zool., Vol. xx, No. 1, pp. 1-62, 4 Pls. 1890. “ > The Compound Eye in Crustaceans. Bull. Mus. Comp. Zool., Vol. xx1, No. 2, pp. 45-140, 10 Pls. 1891, . Parren, WintiaM. The Development of Phryganids, with a Preliminary Note on the Development of Blatta Germanica. (Quart. Journ. Micros. Sci., Vol. xxiv, New Ser., pp. 549-602, Pls. xxxvi A, B, C. 1884. . ——. Eyes of Molluscs and Arthropods. Mittheil. Zool. Station zu Neapel, B. v1, H. ry, pp. 542-756, Taf. 28-32. 1886. ——. Studies on the Eyes of Arthropods. I. Development of the Eyes of Vespa, with Observations on the Ocelli of some Insects. Journ. of Morphology, Vol. 1, pp. 193-227, 1 Pl. 1887. 2. Raruxke, Hernricn. Untersuchungen iiber die Bildung und Entwickelung des Flusskrebses. pp. 1-97, 5 Pls. Leipzig, 1829. Zur Entwickelungsgeschichte der Dekapoden. Archiv. f. Naturgesch., B. vi, pp. 241-249. 1340. . RercnEensacu, Hernricu. Studien zur Entwicklungsgeschichte des Flusskrebses. Abhandl. Senckenberg. Natur- forsch. Gesellsch., B. 14, pp. 1-137+2, Taf. 1-xtv, la-1va, 1vb. Frankfort, 1886. . Ryprr, J. A. The Metamorphosis of the American Lobster, Homarus americanus, H. Milne Edwards. Amer. Naturalist, Vol. XxX, pp. 729-742. j. SCHIMKHWITscH, WLADIMIR. Einige Bemerkungen tiber die Entwicklungsgeschichte des Flusskrebses. Zool. Anz., No. 195, pp. 303-304. 1835, . SHELDON, LiniaAN, Ovum in the Cape and New Zealand Peripatus. Quart. Journ. Micros. Sci., Vol. xxx, New Ser., pp. 1-29, Pls. 1-111. . Smiru, SipNey I. The Early Stages of the American Lobster (Homarus americanus—Edwards). Trans. Conn. Acad., Vol. 1, Pt. 2, pp. 361-381, Pls. xrv-xvu, + Figs. 1-4. 1873. Earlier papers in Am. Journ. Sei. and Arts, 3d Ser., Vol. 11, pp. 401-406, 1 Pl., June, 1872, and in Rept. U. S. Fish Comm. of Fish and Fisheries on the Condition of the Sea Fisheries of the Southern Coast of New England in 1871 and 1872, pp. 522-537. Washington, 1873. Report on the Decapod Crustacea of the Albatross Dredgings off the East Coast of the United States” during the Summer and Autumn of 1884. Ann. Rept. of Comm. of Fish and Visheries for 1885, pp. 1-101, Pls. ~-xx. Washington, 1886. x ¥ Van BENEDEN, PpovuarD, and Brssets, EMIte. Mémoire sur la Formation du Blastoderm chez les Amphipodes, les Lernéens et les Copépodes. Mém.Cour.et Mém. de Say. Etr. publ. parl’Aead. Roy de Belgique, T. XXXIV, pp. 1-59, Pls. I-v. 1870. VIALLANES, H. Etudes histologiques et organologiques sur les centres nerveux et les organes des sens des animaux articulés, Premier mémoire. Le ganglion optique de la langouste (Palinurus vulgaris). Ann. des Sei, Nat. Zool. et Paléontol. t ; MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 46] 62, ———. Etndes histologiques et organologiqnes sur les centres nerveux et les organes des sens des animaux articulés. Cinquieme Mémoire. I. LeCerveaudu Criquet (@dipoda corulescens et Caloptenus italicus). II. Comparaison du cerveau des crustacés et des insectes. III. Le cerveau et la morphologie du squelette céphalique. Ann. des Sci. Nat., Zool. et Paléontol., I. rv., Nos. 1-3, vir Ser., pp. 1-120, Pls. 1-6. 1887. 63. Warasr, S. On the Morphology of the Compound Eyes of Arthropods. Studies fr. Biol. Lab'y of the Johns Hop- kins University, Vol. Vv, pp. 287-334, 7 Pls. 1890. 64. WaLprEYER, W. Eierstock und Ei. 65, Witson, Henry V. On the Breeding Seasons of Marine Animals in the Bahamas. Johns Hopkins University Circulars, Vol. vimt, No. 70, p. 38. 66. Woop-Mason. Stridulating Crustacea. Remarks of Mr. Wood-Mason at the November meeting of the Entomo- logical Society of London. Nature, Vol. xvin, p. 53. 1878. 67. WHEELER, WILLIAM M. The Embryology of Blatta Germanica and Doryphora Decemlineata. Am. Journ. Mor- phology, Vols u1, No, 2, pp. 291-386, Pls. xv-xxr. 1889. APPENDIX I. THE LIFE HISTORY OF STENOPUS. _ Since this paper was written Chun has described (Die pelagische Thierwelt in grésseren Meere- steefen, Bibliotheca Zoologica, 1, 1888) a small transparent crustacean which he calls Meiersia clavigna. It occurs at the surface and also at various depths down to 600 M. A comparison of his description and figure (Taf. tv, Fig. 6) with the Stenopus larva shown in Pls. 1x and x of this memoir shows that Chun’s Meiersia clavigna is undoubtedly a Stenopus larva, a little older than the one shown in Pl. x. (W. K. B.) It is suggested at the bottom of page 340 that the cement by which the eggs are fastened to the abdomen may possibly come trom the oviducts. According to recent observations of Cano (Mittheil Zool. Stat. Neapol., 1X, 1891; abstract in Journ. Roy. Mic. Sov., No. 83, 1891) this is derived from cement glands situated in Stenopus under the epidermis of the pleopods. 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 through which spermatozoa reach the ova, In order to reach the eggs the sperm cells probably pass through pores in the chorion. This paper was written in the summer of 1888, before I had seen the report of Spence Bate on the Challenger Macrura (Report on the Crustacea Macrura dredged by H. M.S. Challenger during the years 1873~76, Zoology, Vol. xxtv, p. 209, Pl. xxx, 1888). The Challenger brought home only two specimens of Stenopus hispidus, one fiom erate: Fiji Islands, and one from Bermuda. Spence Bate says that Stenopus 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 Squilla greenlandica of Seba, which appears under several names, may be the same as Stenopus hispidus. “The genus,” says Bate, “thus appears to inhabit regions so widety apart as Greenland in the north, the Bermudas and Mediterranean in the west, and the southern coasts of India and the Fiji Tslestae 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, despite this cosmopolitan range, it has not been recorded as having existed in any geological formation.” While the conelusion that the Arctic form is a Stenopus may be correct, it seems highly im- probable that it is specifically related to Stenopus Atepuias. There is no evidence at least to show ~ that this is the case. Bate figures a late egg embryo of Stenopus (Fig. 40, p. 212), and erroneously concludes that the animal has a short metamorphosis and that it hatches as a “‘Megalopa.” He also gives a draw- ing (PI. xxix, Fig. 2, v.) of the first larva of Spongiola venusta (a prawn which is placed by Bate in the tamily Stenopide). This is clearly not a zoea, but a protozoea, as is better shown by the sketch of the recently hatched larva (Fig. 42, p. 216) by von Willemoes Suhm, and the strong resem- blance which it bears to ne protozoea of Bionbpus hispidus is very striking (compare with Pl. vu, Fig. 11, of this paper). 462 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. According to Bate the branchial formula of Stenopus was first elucidated by Huxley in his memoir on the classification of crayfishes (Proc. Zool. Soc., London, 1878). There are six pleuro- branchie ; eleven arthrobranchiz, five of which are anterior and six posterior; one podobranchia, and six mastigobranchie, of which the first is the only efficient appendage. Spence Bate states that after careful comparisons he failed to find specific differences between specimens from the Eastern and Western Hemispheres. ERRATA. As numerous errors have unavoidably occurred in this paper, I will correct the more important of them. Page 341, line 8, for *‘ Pl. vir” read Pl. x. Page 341, line 13, for ‘* Lesneur” read Lesueur. Page 343, line 2, for ‘‘ cells have spread more rapidly at a given point on the egg” read cells have increased more rapidly over a given area of the egg. Page 343, over table for ‘‘ Temperature 80° F.,” read Temperature 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, line 20, for ‘‘ Fig. 10” read Fig. 11. Page 345, line 30, for ‘‘ Fig. 11” read Fig. 10. Page 345, line 38, for ‘‘ the first and second maxillipeds” read the amd and third maxillipeds. Page 346, line 31, for ‘‘ larger than telson” read longer than telson. Page 347, line 16, for ‘‘ x11 and Fig. 40” read x1 and Fig. 39. Page 347, line 29, for ‘‘and 38” read and 39. Page 347, lines 37 and 41, for ‘‘ Pl. x1” read Pl. x11. Page 347, line 40, for “ Figs. 43, 45” read Figs. 43, 44. Page 347, line 47, for ‘‘ Fig. 47” read Fig. 46. Page 348, line 15, omit “‘errinem--_- -- larve. Page 348, for lines 32-34 read: Body nearly cylindrical; tergal surface covered with spines. Carapace witli prominent laterally compressed rostrum and distinct cervical and branchio-cardiae grooves. Outer antenne with long bristle-bordered scale bent under the inner antenne toward the middle line, Second maxillipeds with setig- erous lamina, attached to endopodite. Page 348, line 46, for ‘‘ a marked transverse fossa” read a marked cervical groove. Page 348, last line, for “‘ transverse furrow ” read cervical or mandibular groove. Page 349, line 17, for ‘‘ Fig. 40” read Fig. 39. Page 349, line 21, for “ their inner borders which meet in the middle line” read the inner honda 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 chelw ” read bearing the great chele. Page 390, first line, 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 350, line 9, for ‘* Fig. 41” read Fig. 40. * Page 350, table, tenth line from bottom, for ‘‘ Length of chela” read Length of chela of same. Paye 352, line 10, for ‘‘hartschilig” read hertschalig. Page 352, tenth line from bottom, for ‘‘Crustaces, Arachnidses” read Crustacés, Arachnides, APPENDIX I. PARASITIC FUNGUS IN THE EGG EMBRYOS OF ALPHEUS SAULCYI. The remarkable parasite of Alpheus sauicyi, to which allusion was made in Part First of the Memoir on the development of Alpheus, is illustrated in Fig. 199, Pl. Lim. 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. longicarpus, 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. - MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 463 The sections of these embryos were very kindly examined by Professors Joseph Leidy and W. G. Farlow. In reference to them Dr. Farlow writes as follows: The parasite is certainly of great interest. I cannot find any description of it in botanical literature, although it appears to be a fungus belonging to Chytridiacex. The fungus has no mycelium, but is composed of single cells of various sizes. In a section like that shown in Fig. 199 nearly one hundred large cells or cysts can be counted, and it is seen that the peripheral 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 with the parasitic growths and showed traces of degeneration. The parasitic bodies are mainly (1) large naked cysts or encysted cells, and (2) very small spore-like bodies. The naked cyst (¢. s., Fig. 199) is a thick shell which has collapsed and curled up with the eseape of its contents. It is yellowish and is unaffected by staining reagents. The surface of the cyst is covered with very uniform, short projections or tubercles, which refract the light in a characteristic way. Other eneysted cells contain a protoplasmic reticulum (es'), and there are very similar but smaller bodies which are either naked or possess but a slight cuticular wall. These encysted bodies just described possibly represent zoosporangia, and give risé to the myriads of minute spores which occur in close relation with them. The spores (Fig. 199, sp., represented by small black dots) are minute, oval, and highly refractive. 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- bryonie cells which have undergone modification. Occasionally one of the cysts appears black (es?), which is due mostly, if not wholly, to refraction. According to Goebel, reproduction in the Chytridiee 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 zoosporangia. These give rise to swarm spores, which are liberated into the water. The Chytridiee are described as parasites on other aquatic plants, Fungi, Algze, and Phanerogams. _ According to De Bary resting spores are known to occur in certain species. These develop directly into sporangia or produce them after a short intermediate stage, and appear to resemble the sporangia in 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 in the Introduction published in the Johns Hopkins University Circulars, No. 97, April, 1892. The part relating to the embryology 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 Alpheus minus of Say 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, May, 1892, ‘Size, = ameters.) twice natural > i (Enlarged eight a i) E NATIONAL ACADEMY O. TH. & MEMOIRS OF Dorsal view of a specimen of the gray variety of Gonodactylus chiragra, ¢ Ad =) =} on) 3) < Nee Yore , del. FAH ALPHEUS SAULCY!I, VAR. BREVICARPUS. wa See. en Lg ae y 472 Dorsal view of the saat male Ricnomss hispidus. Nassau, N. P., June, 1887. L=13in. L. first Excepting the brilliant pigment bands the body and appendages are nearly white,’and could be Puate V. antenna, exopodite—3{ in., endopodite—33 in. L. second antenna= =4U in, x13. better represented against a black background. The arching flagelia of the antennz are greatly foreshortened, and the spines and sete are of necessity we empha-— sized in a pen and ink drawing. “SNGIdSIH SNdONALS “pop 2rrtapy FY] nm) many 2 eytnstonar MATOYTNAS BEERS “ ha 4a » ier ae Te Pid) say ler BA tite ae iy a His « © 0), fy . Si . i Ane i, De 3 i : PA iit awe oar en al Ba See oy ty ancien arches CRS L: eles gika me dD “4. 1 Shell A a ~~ -. 4 oy ry. . . : eat ae 7 ren aed? Poy ery a Ps. 474 Fig. Fie. Fic. Fie. Fig. Fic. Fie. Hm Oo bo (6 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. - Puate VI. . Part of section of egg, showing the male pronucleus. 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. . Section of egg with four nuclei, none of which are at the surface. 152. . Part of same section, showing the nucleus and surrounding protoplasm and yolk. x 276. . Lateral section, cutting yolk segment on a level with the disk-shaped nucleus. Compare Fig.5 a. Hight-cell stage. Age about 12 hours. x276. Section through egg in eight-cell stage. Compare Fig. 6. Age about 15 hours. x 152. . 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. x78. Section of egg in the fourth segmentation stage. Sixteen cells. x 152. Fic. 8. Fifth segmentation stage. Age, 19 hours. Cells not yet at surface. x 152. Wic. 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 egg envelopes (removed, except in Fig. 5). Ep, ectoblastic cell. ‘ Ig, shallow pit of invagination. y.¢., yolk spherule. Plate VI. Fig.6. ies PPM) CPS ERD Dect NO co FH. Herrick, del. Sac 18 Wilbelon Lather Co Mew York STENOPUS HISPIDUS. r~ wa Pa Ine \e-< S — Ss, 7 ¥ Pink | . - # Ake yt + a= wy ai MEMOIRS OF THE NATIONAL” ACADEMY OF SCIENCES. Piare VII. . | Pg nee Fic. 10. Left second maxilla of larva at the point of hatching, before the first molt. x 276. Com- ; pare with Figs. 25 ané 21. Fie. 11. First swimming larva, after the first molt, seen from below. Pigment cells, brown. © L= 7, in. (measured from tip of rostrum to median notch of telson). Length of rostrum =;65 in. x70. = Fie. 12. Right first maxilla of first larva, seen from the outer side. Sete welder thai Compare : : Figs. 19, 25. x 276. ; Fie. 13. Telson of larva before first molt, seen from below. Compare Fig. 11. The setie are invaginated and covered with a loose cuticle. x 276. Fic. 14. Right first maxilliped of larva on the point of hatching, seen from the outer side. Sete invaginated. Compare Figs. 22,25. 276. = Fig. 15. Labrum and right mandible of larva, seen from above. 276 ; 7 Fig. 16. Right third maxilliped of larva on the Bane of hatching, seen erate the outer side. Com-— pare Fig. 25. 276. : REFERENCE LETTERS. ; H = a, ontermost spine in telson of larva at the point of hatching. 3 d, equivalent of a in first locomotory larva. Lb, labrum. >. = ee ee ee eee ee, ee ee Sack eh Witdeis Lamers phiog Co New York FH. He STENOPUS HISPIDUS. ; 478 MEMOIRS OF THE NATIONAL ACADEMY OF SC! x rate, Pah ee RUATE SV LED Wiser i Fie. 17. Second larva after second molt. L=,%}; in. x70. fe 73 ee Fic. 18. Left mandible, outer side, of second larva. x 276. ig ace Fie. 19. First maxilla of second larva. x 276. ye ae eae Fie. 20. Telson of second larva, seen from below. x70. ; bey Fic. 21. Left second maxilla of second larva, seen from the outer side. x276. Seas Fic, 22. Right first maxilliped of second larva, seen from the outer side. x 276. _REFERENCE LETTERS. ee po — i 9 9, gastric gland. ness ; ae . . . . the dotted line in Fig. 20 points to the outer spine, the equivalent of d, Fig. 11. mies Plate Vill. At a f BANG } PA NAY o My = we = Le 4 aa ee Say = ss va \\ \y / EH Merrick det. STENOPUS HISPIDUS. ail | a? ae # MEMOIRS OF THE NATIONAL ACADEMY OF na, drawn from — - 4 | = "d : ree ! Ie “i jt Pete ie ‘. : ' 1 al 5 i Paty oe | j * i ie’ sp i | “ Foe) y fai ‘ } SI a | \ t PS f } j \ ; / I | \ j ots PD ~ } ‘ We Se cree life by | Advanced pelagic larva of Stenopus hi. Se i / pe . eae Beaufort, North Carol ‘us, trom “W. K. Brooks. WK. Brooks, ded. STENOPUS Plate IX. nig Ce New York ~ ‘ tue beh Say y W.-K. Bre drawn from life b 4 i aS a a 8 8 q | A ; A IS & © mM : ie) a al a Dorsal view of a larva like the one shown in Plate TX, Plate X W K. Brooks, del. STENOPUS : i ie CoS eee a Nit SOT 6 AURIS NOs aah eats Bart: 57 Ae eee 484 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. ® Puate XI. ; Fic. 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. Fic. a Right first antenna of alder larva. x70. Fic. 27, Profile view of hinder end of abdomen of same larva. x28. Fic. 28. Second maxilla of same larva. x 276. Fic. 29. Mandible of same larva. x 276. Fic. 30. First maxilla of same larva. x 276. Fic. 31. Portion of third maxilliped of same larva. x 70. Fig. 32. Terminal segment of Second pereiopod of same larva. x 70. Fic. 33. First pereiopod of same larva. x70. ‘ : Fie. 34. Portions of third, fourth, and rudimentary fifth pereiopods of same larva. x70. REFERENCE LETTERS. A, I, first antenna. A. IT, second antenna. Md., mandible. Vapd. I, III, first and third maxillipeds. R., rostrum. Th., Th. 1, first maxilliped. Th. 3-Th. 5, third to fifth maxillipeds, 1, first maxilliped. Plate X/ Fig. 27 Ca, ic = = a at Fig52. FH. Herrick, del. Sackett & Wei Latgraphing Co: New Yors STENOPUS HISPIDUS. ‘> —— ~~ : é ee IOTEY S o *. — 5-4) ny . iim wits <= eo 4 - dex tA ie ae: eh ae “Sea. wed Prare XII. a Fic. 35. Older larva, taken in the tow-net outside of Nassau Harbor May 7, 1887. L=9™™. L. — ey of eye-stalk=2™™. L. between eyes=4.7™. x15. The long flagella of the antenne 3 are conventionally represented to bring them into the plate. They trail above and . behind the animal as it swims eee the water. ‘ Plate XI. Figure 33. FH. Herrick, del. cts Wiens Labgaghg Ca Bw Yah STENOPUS HISPIDUS. cas Sige liar Grid o. AE ee 7 sik. Ye i af ore s > fz ra af 4 iy 488 . First maxilla, outer side. Adult male. »15. . Lateral view of carapace of adult male. x5. . Left mandible, outer side. Adult male. Seale re <2 - Stalk and portion of flagella.of left first antenna, seen from above. Aduit male. x5. oes . First right pleopod of male, outer side. x14. 5 . Left second antenna with flagellum cut off near its base. Adult male. Seen from - Second maxilla of adult male. x 14. : . Right first maxilliped from outer side. Adult male. x 14. - Right second maxilliped, from outer side. Adult male. x 14. - Right third maxilliped, from under side. Adult male. SOL aera ate - Right first pereiopod, under side. Adult male. x5. . Right fifth pereiopod, under side. Adult male. x5. = : - Prats XIII. above. x5.. = Pate XTIl FH. Herrick, del. acc W thai Latregrazing Ce New Yor STENOPUS HISPIDUS. ‘. 5 GZ "ss A Digan oe. oN at ee iat vs ie wea tS 490 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. XN +2) PraTrn oc by: : x Metamorphosis of Gonodactylus chiragra, drawn from life by W. i Brooks. Fic. 1. Dorsal view of egg just befere hatching. ~ ~ Fic. 2. Front view of the same egg. 3 Bao Fie. 3. Side view of the larva immediately after hatching. Fie. 4. Side view of the same larva after the first molt. | Fic. 5. Side view of the same larva after the second molt. z Fic. 6. Dorsal view of the larva at the beginning of its pelagic life. 3 ee laa J \ ° — \ ~ a \ e ~ — < = ~ - = * 2b { Y é . ~ Sie ay , —_ ¢ a — yee ; ‘ ¥ OY ce ae ot a or - 2 by 7 Sea Z Plate XIV. WK. Sroaks, del. GONODACTYLUS CHIRAGRA. 492 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. | = 4 Di: PuatTe XV. Metamorphosis of Gonodactylus chiragra, drawn from life by W. K. Brooks. ce : Fic. 7. Dorsal view of the larva shown in PI. xIv, Fig. 3. - Se _ Fic. 8. Ventral view of the same larva. ere? Fic. 9. Dorsal view of the larva shown in Pl. xtv, Fig. 4. 4 ot Fig. 10. Ventral view of the larva shown in | Pl. 7M Fig. 5. Fic. 11. An older larva in dorsal view. Fic. 12. Same in ventral view. Fic. 13. Raptorial claw of a still older larva. . ? AV, Plate WK. Brooks, del. GONODACTYLUS CHIRAGRA. 494 Fig. FIG. Fig. Fic. Fie. Fig. Fic. Fie. MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Puate XVI. Metamorphosis of Alpheus, drawn by W. K. Brooks and F. H: Herrick. . Third larval stage of Alpheus minor from below, drawn by W. K. Brooks. . Second larval stage of Alpheus minor, about one-tenth of an inch long, drawn from below by W. K. Brooks. - . Telson of the Nassau fourm of Alpheus heterochelis during the second larval stage, drawn at 10 a. m., April 17, 1887, by F. H. Herrick. . 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.) . First and second maxille 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 Pl. x11, Fig. 3. ‘ . First maxilla of Alpheus minor during the first larval stage, drawn at Beaufort, June 2, 1881, by W. K. Brooks, D. 2. . Second maxilla of the same larva. . Mandible of the same larva. Mate XVI Brooks, & Herrich,del ALPHEUS J f ; a . oa ~ 2 Se ee ‘- Pi oie Py as ae Ry eee DS rata xy ° nes ae ‘ ‘ = La! pierec vere: mR. MOK Feral ate cnrn eK, ice YB b rie ap ASO ERY o Dy tiie ah oh on ee oe ue gil ope ee ee | x 7 "tty Eb rea tage inl ad Baa af Sw Wie eee oe Ser 496 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Pirate XVII. poe Metamorphosis of Alpheus, drawn from nature by W. K. Brooks. 5 Fic. 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. Fic. 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. Fic. 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 Pl. xx, Figs. 2 and 3. Plate XVII WE. Brooks, det. Sacer Widsetnas Labegrasting Co Mew York ALPHEUS = ae ae. o Lele Oe Pre is > ae Le > © eS is Pas \ 498 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES, Prare XVIIE Metamorphosis of Alpheus, drawn by W. K. Brooks from sketches by F. H. Herrick. Fic. 1. Side view of first or second larval stage of Alpheus heterochelis from Nassau, drawn oa the night of April 15, 1887. Zeiss A. camera. 4 <3 ; Fic. 2. Ventral view of the third larval stage of Alpheus heterochelis from Nassau, drawn aun 18, 1887. at. Fic. 3. Ventral view of fourth larval stage of Alpi heterochelis from Nassau, ‘drawn APS are 21, 1887. eee Fic. 4. First ramen of the first larval stage of Alpheus minor. Plate XVIII Brooks, & Herrich,del . ALPHEUS 4 \ - * 7 ip eer Phee shee teria’? SW bereits Free wits cd RATS Beret UR ey ~ ; “ . bi 7 rl % Mote * rind ‘ he ; a at fs eo wnhte PA Fa! Barwa Myers Pr tey parstt af — ; hi , aR iets CO Sie ta ESAT ee Foran nls al 9h a4 “qtie i : visielat 7 i ie : ° ya J WIR eee ees Thre eee: vs oi . ae BPP Paley a) 1 ken wf - = . h ae ey oy eh TET Agra Sint bee Rt et fijecchs © Ps as ? oy 500 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES, = & Prats XIX. Metamorphosis of Alpheus heterochelis at Beaufort, North Carolina, drawn from nature by W. Ko Breoks. Fic. 1. Ventral view of the larva immediately after hatching. ; : : Fic. 2. Side view of the same larva. ‘ < Fic. 3. Dorsal view of the antennule of the same larva. Fic. 4. Ventral view of the antenna of the same larva. ; = 3; Fic. 5. Mandible of the same larva. ; es Fic. 6. First maxilla of the same larva. : : : Fie. 7. Second maxilla of the same larva. Plate XIX. ~~ = = FSO SSS eS Sask ot & Wildehes Lathograyneng Co Mew York W.K. Brooks, ded. ALPHEUS ae a. a ee, eas VRPT IS gE Mn ope Oa aN at ep eee ae fer) oY, " 3} Lan y dat = he £ ba ra = atl “a 4 & Mein : 502 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. EO hehe i {= # PLATE, Metamorphosis of Alpheus heterochelis from Beaufort, North Carolina, drawn from nature by W. K. Brooks. - Fie. 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 Pl. xvu, Fig. 3, and a little older than that shown in Fig. 3 of this plate. Vic. 3. Ventral view of a larva little younger than Fig. 2 Fre. 4. Telson and swimming appendages of the larva shown in Fig. 3. Fic. 5 First maxilla of the same larva. Fic. 6. Second maxilla of the same larva. Fig. 7. First maxilliped of the same larva. Fie. 8. Second maxilliped of the same larva. Fic. 9. Third maxilliped of the same larva. :— Plate XX. WK. Brooks, ded. ALPHEUS u awh a “elie. ahi At Rie tg PS Ween pay ree a = oh Pan oa ie “ax eo Bele, a ak tA: we ey $ ue “ Ny Abe Beaty Wipes . ie per rer Ciaita er At ) Tear reps rE erie iabakasr 4 or Boots si Saha = ish gi ures ei sn cies Ses soh ‘i er Ronee ee fi ae, MN £4 ns O est a ‘? ure rh ee 504 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 6 eee Puate XXI. Fic. 1. First larva of Alpheus saulcyi, var. brevicarpus, from “loggerhead” sponge. Hatched at 4 p. m., June 10, 1887. A small amount of unabsorbed food yolk remains in the stomach. x 26. 7 Fic. la. Line to indicate length of larva. L.=3.5™™. Fie. 2. Second larva of same, from brood hatched on evening of June 8. Food yolk neraly absorbed. About twenty-four hours old. x 26. Fie. 2a. Line to show length of larva. L.=4™™. Fic. 3. Head of young from same brood. Four days old. x52. f1G. 4. Right first pereiopod of larva of A. saulcyi, var. brevicarpus, before the molt preparatory to stage shown in Fig. 1. Seen from inner side. x52. Swimming hairs of exopodites rudimentary. ; Fic. 5. Egg embryo of A. sauleyi, var. longicarpus, nearly ready to hatch. The large chela of the left first pereiopod is conspicuous below the antennee. x46. Fic. 5a. To show natural size of the same. Slightly too large. Dimensions: ;45 78> inch. Fie. 6. First and second maxilla of first larva (Fig. 1) before preparatory molt. The parts are gloved with the embryonic skin, which is usually cast off at the time of hatching. x 227. Fic. 7. Left first pereiopod of same, seen from inner side. X52. Fie. 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. Fic. 9. Telson and rudimentary uropods, seen from below. x 52. Plate X.X/ FH. Herrick, del. ALPHEUS SAULCYI —_. = =". s a. o> s ¢. Ot * eit aia eee 1 '=bo5 bs: 506 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. | P Prats XXII. Fic. 1. Left second pereiopod of first larva of A. saulcyi, var. brevicarpus, from inside. x 64. ; $ Fic. 2. Left third pereiopod of same, from inside. x 64, ; Fig. 3. First maxilla of first larva of A~saulcyi from brown sponge. x 255. Fic. 4. Left second abdominal appendage of first larva of Alpheus sauleyi, var. brevicarpus. x 64. 24. Fie. 5. Left first abdominal appendage of the same. x64. = Fie. 6. Rostrum of the same, seen from above. x 64. Fic. 7. Right second antenna of the same, seen from below. x 64. : Fig. 8. Right first antenna of the same, seen from above. x64. ~ Z Fic. 9. Second antenna of young of Alpheus saulcyi, var. brevicarpus, six and a half days old. x 64. Fic. 10. First antenna of the same. x 64. $ i ’ Fic. 11, Head of male of Alpheus saulcyi, var. longicarpus, trom “ loggerhead” sponge. Median Ba spine of rostrum wanting. Drawn from life. L.=5.5™™, 31. Fie. 12. Mandible of first larva of A. saulcyi, var. brevicarpus. x 255. Fig. 13. Left second antenna of male of A. sauleyi, seen trom below. No.8 of Table I, p. 385. x33. Fic, 14. Left second antenna of female of A. saulcyi. From No. 9 of Table I. Xd: ; Fie: 15. Small chela of larva of A. sauleyi, var. brevicarpus, shown in Vig. 17, at time of hatching. Compare this with the same appendage of the adult. x64. _ te ‘Fig. 16. First pereiopod (small chela) of young of A. sauleyi, var. brevicarpus. From green sponge. ; Compare this with Fig. 3, Pl. xxiv. x 64. ; : Fic. 17. Front of a larva of A. sauleyi, yar. longicarpus, which was hatched April 25. Drawn ) under pressure; eyes slightly distorted. Equivalent to the ordinary third larva, Fig. Te 8, Pl. xxr x64. Fig. 18. Part of stalk of right first antenna of male of Alpheus saulcyi, seen from below, showing the auralscale. The median eye is seen on the right, between the basal segments of the antennules. From No.8 of TablelI. x26. ) Plate XXII Sacken Widanions Laegraciuny Co New Yow FH Herrick, del. ALPHEUS SAULCYI, Ae ‘ . a ie ve. he} ye vite Tile janet aS ae Pir ASG aS ies ff f ml ee See LTE | - Ae <> ¥ Aires 7 3 ; TC oat a ain OD ; Litiieits Sighs The 508 . Right second pereiopod of male of Alpheus saulcyi, var. brevicarpus, seen from the outer | . Terminal segments of right fifth pereiopod of the same. x33. . Left mandible of the same, seen from the outer side. x 64. - . Left first antenna, and left compound eye of the same, seen from above. x33. . Left third maxilliped of the same, seen from outer side. x33. . Right second maxilliped of the same, seen from the outer side. x 64. . Right first maxilliped, seen from the outer side. x64. . Right second antenna of the same, seen from above. x33. oe Puate XXIII. side. x33. | a oe FH. Herrick ,del . ALPHEUS SAULCYI. Plate XXt/1 Fig 2. r ‘ ie ma oat a Nh \— 3 “ es Se #ig Pa a | i ERNE T Se : 510 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Prare XXIV. { : Fic. 1. Right fifth pereiopod of male of Alpheus saulcyi, var. brevicarpus, seen from outer side. x33, = Fie. 2. Small chela of male of A. sauleyi, var. longicarpus. From No.9, Table I. x33. aA _ Fic. 3. Small chela of male of A. sauleyi, var. brevicarpus. From No. 8, Table I. Compare with | : the typical form of the other variety, shown in Fig. 2. x33. Fie. 4. First pleopod of male of A. sauleyi, from “loggerhead” sponge. x33. ae Bat, Fic. 5. Left first pleopod of femate of A. sauleyi, from “loggerhead” sponge. A single egg is seen, we attached to three hairs of the protopodite. The hairs are coated with glue, and the | gluey threads are twisted into a chord, which is continuous with a thin sheet of this i substance (the membrane of attachment or secondary egg-membrane which envelopes 5 > the egg). Below is seen a single hair, from which an egg has broken loose. Drawn s from an alcoholic specimen. x33. Fic. 6. Right second pleopod of larger female of A. saulcyi, showing a number of eggs attached, seen from behind. x14. Fic. 7. First maxilla of A. sauleyi. Endopodite bent out of position, to a point below the large a coxopodite. x64. é ; Fie. 8. Large chela of female of A. saulcyi, from “loggerhead” sponge. Compare with the Brea. = is carpus shown in Pl. tv. x33. ie: Fic. 9. Right second maxilla of A. sauleyi, seen from outer side. x64. (Sait Pit a a ost i Pree Ws ae fee a ah ae ee a eee terete) we SO a Plate XXIV. PO eee eee yee eee Sackeo & Wilbelms Lithographony Co New Yarie ALPHEUS SAULCYI, FH. Herrick, del. * . phe Nee Pi ely , = F<» a bars = a Vaal hog EA eon ‘ “a > Ne ~~ La Fatt t dA et ee ase 512 Fic. FIG. Fic. Fic. Fic. Fie. Fie. 6. The eee z an, so ee tae! — + i tO ee ah. Sl al na “ om . = . he Sd rng at « nied : Sey ska pa Sie gre F> r Sit SEs ee EN Te re me MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. PuatTeE XXYV. . Surface view of segmenting egg of Hippa talpoides. Thirty-two yolk pyramids present. x 38. . Embryo of Hippa talpoides, showing optic disks and thoracic-abdominal plate. x 38. . 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. x 281. . Section of egg of Hippa talpoides in yolk segmentation. Sixty-four yolk pyramids pres- ent. x70. . Part of segmenting egg of Alpheus minor, showing a single large nucleus and two smaller nuclei. Compare with Fig. 23. x 281. : Central portion of transverse section of ovary of the lobster, corresponding nearly to that shown in Fig. 3, 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. Egg-nauplius embryo of Hippa talpoides. Appendages appear as simple buds. x38. Fic. 8. Post-nauplius stage of Hippu. Abdomen bilobed at tip. Buds of at least three pairs of post-mandibular 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. Ab. P., thoracic abdominal plate. = B. C., blood cell. Bl. S., blood sinus. Ch., chitinous eggshell. Ch. W., limiting membrane of blood sinus. Ct. S., ovarian stroma. EL. f., egg follicle. F. C., egg follicle. Ger., germogenal area. I, E., ovarian stroma (undifferentiated). 0, o'-o7, nuclei of ovarian stroma and developing eggs. O. D., optic disk. : O. L., optic lobe. Y. P., yolk pyramid. Y. S., yolk spherule. Vae., yolk vacuole. Plate XXV. HIPPA,HOMARUS AND ALPHEUS. = 514 MEMOIRS OF THS NATIONAL ACADEMY OF SCIENCES. ! PLate. XXVI_ . Fie. 9. Section through segmenting egg of Alpheus sauleyi. Hight cells present. Yolk unseg- mented. Egg membranes diagramatically represented. x 70. : Fic. 10. Surface view of the same. Sixteen cells present. Yolk pyramids formed. The peripb- eral nuclei are seen through a thin layer of yolk. x 70. Fic. 11. Transverse section through 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 fiftieth of an inch. Contents of ovarian egg, one thirty-seventh of that of the extruded egg. x 281. Fig. 12. Section through segmenting egg of Alpheus minor, from Beautort, North Carolina, show- : ing nests of nuclei. x70. : Fic. 13. Swarm or nest of nuclei, like those of preceding figure. x 251. Fic. 14. Section through egg of Alpheus minor, cutting segmentation nucleus. Nucleus elongated, with irregular, indefinite boundary. x 70. REFERENCE LETTERS. Al. C., alimentary canal. B. C., blood cell. B. 8., blood space (possibly unnaturally distended). Ch., chitinous egg envelopes. D. A., dorsal aorta. e, el, young ova. F. E., ovarian stroma. F. £.', follicular epithelium. F.C., follicular epithelium. Ger., germogen. Ger.', position of germogen in ovary, with ova nearly ripe. G. V., germinal vesicle. O. W., ovarian wall. SS, swarm of nuclear bodies. Vac., yolk vacuole. Vit., vitellogen. x, cell shown in Fig. 30. Y. P., yolk pyramid. ~ . 2 s Plate XXVT. F-H. Herrick, del. ine 8 Wiens sageghng re York ALPHEUS SAULCYI AND A.MINUS. Page ae ard & > — = Oe aS 7 inc} yee as VE ¥ ". tana" tom. PA Jae ee se thie Te ertads vivo dy a] 4 [igitergh &ovi 516 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. ~ 7 Puate XXVIII. Fic, 15. Section of egg of Bahaman variety of Alpheus heterochelis in typical yolk pyramid stage Sixty-four cells present. x70. Fic. 16. Segmentation nucleus of egg of A. sauleyi, nearly central in position. x 277. Fic. 17. Section of an egg of A: sauleyi, which was normally laid but unfertilized, showing the 5 female pronucleus. x70. ’ Fie. 18. Degenerating nuclei containing spore-like bodies, from the egg-nauplius embryo, the structure of which is shown in Pls. XLI-XLIlI. Xx610. Fic. 19. Blood cells of adult Alpheus. x 610. ; Fic. 20. Endodermal cells from the ventral wall of the primitive alimentary cavity of Astacus fluviatilis. After Reichenbach (54) Taf. vin, Fig. 67. This is taken from the egg- nauplius stage to show the origin of ‘‘secondary mesoderm.” The elements here marked m', k are described as cells which have originated from the endoderm, and completed their metamorphosis into ordinary mesoderm cells. These may be com- pared directly with J, Fic. 18, and s, s’, Fig. 21, from the egg-nauplius of Alpheus sauleyi, and are rather to be regarded as nuclear bodies in the earlier stages of retrogressive metamorphosis. x 256. Fic, 21. Part of transverse section through the foregut of the egg-nauplius of Alpheus saulcyi, to show the degenerative cell products. x 610. REFERENCE LET'lERS. A. Y.S., altered food-yolk. Ch., chitinous egg membranes. ec., ectoblast. i., nuclear body, with vesicular chromatin mass. k, k,l, m, m'-, nuclear products in yolk. Mes., mesoblast. N., N.', nuclei of entoblastic cells, n., nucleolus of entoblastic cell (not clearly shown). OL., oil drop. Ret., protoplasmic reticulum. S, 8, 8?., degenerative products. Sep., cleavage plane. Std., foregut. Vac., yolk vacuole. Y., yolk. Y. P., yolk pyramid. Y.S., yolk sphere. Plate XXVII. F-H. Herrick, del. Sach a8 Wilhelm Lthegpraphu Co. New York ALPHEUS AND ASTACUS. Res Wn ee getting ree a ne Pe Pe tS ee ee ee ez etn uate Sah Nae , . ~ 2 ~ ane ey " meray J e : % Ee Des : ; - = B - a re 518 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Pirate XXVIII ‘ : Fia. 22. Part of section of segmenting egg of Alpheus minor from Beaufort, North Carolina, show- ing nuclear body in clear area. x 277. Fic. 23. Swollen, probably degenerating, elements, from segmenting egg of A. minor. X27. Fie. 24. Section through base of yolk pyramid of egg of Palemonetes vulgaris. About sixty-four cells present. x 277. Fies. 25, 26. Two: successive sections through clear area in segmenting egg of Alpheus minor, showing degenerative products and nuclear bodies in process of breaking up. x 277. Fic. 27. Part of section through segmenting egg of Pontonia domestica, betore cleavage of the yolk. The egg contains three nuclei, one of which is seen to be in karyokinesis. x 277. Fic. 28. Part of section of an Alpheus egg in same stage as that shown in Fig. 9. Cell dividing indirectly and in horizontal plane. x 277. Fria. 29. Section of-egg of Alpheus minor, probably at close of segmentation. x 277. Fic. 30. Enlarged view of cell x, and part of section shown in Fig. 9. x 277. REFERENCE LETTERS. Ch., egg membranes. N., nucleus. P. A., protoplasmic area. P.N., perinuclear protoplasm. SO, SC, degenerating cell products. Y, yolk. Y. B., yolk ball. Y.8., yolk sphere. Vac., vacuole. ALPHEUS AND PONTONIA. Plate XXVIII A Wittens Laeogragrony Co. Mew York eS 2 e- ~~ x , Lae ie > od ge abst . : att & 520 Fie. 31, Fig. 32. Fic. 33 Fig. 34, Fie. 35. Fie. 36. MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Puate XXIX. Part of section of egg of Bahaman variety of Alpheus -heterdchelis, showing two yolk pyramids. Same stage as Fig. 15. Sixty-four cells present. 277. Part of transverse section of egg-nauplius of A. saulcyi, showing the fold of one of the antenne and the mesoblastic cells and degenerative products contained within it. x 610. ; - Wandering cells in yolk above the same embryo, showing protoplasmic union. x 610. 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. : Part of transverse section of older embryo, showing blood cells and wandering mesoblast cell (Mes.). Eye-pigment beginning to form. x610. Part of longitudinal section of embryo shown in Fig. 153, to show the degenerative prod- ucts of the dorsal plate. x610. REFERENCE LETTERS. App., appendage. ay A. Y.S8., 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. Mes., 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. 7 _» , XXIX Plate Sep. rps a aeue: @ App. FH. Herrick, del. ALPHEUS 7 _?), 22081 Soe 2. Baas - © eo ok * aig , Me Oe ee, RN ae Sa ees git oo ae a me Saal ae Pan eee gee wert f r Oe hos ae i Z ; ax a 3 a 522 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. — . + PATE OKO Fic. 37. Part of section of egg before invagination stage, showing primary yolk cells. All the — figures on this plate, excepting Fig. 46, refer to the Bahaman form of Alpheus hetero- chelis. X27. Fic. 38-44, Consecutive 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. x70. Fig. 45. Section through the same egg, showing semidiagrammatically the structure of the yolk. x 70. ; Fic. 46. Section through the egg of A. sauleyi at a slightly later stage, but before invagination. The blastodermie 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 Rye and a secondary cleavage has occurred below the surface. x 70. Fie. 47. Surface view of the side of egg, corresponding ve the germinal area in nearly the same stage. x70. Fie, 48. Tangential section, showing tilastodarmic cells of same egg. x 277 5 REFERENCE LETTERS. a, a7, cells migrating from blastoderm into the yolk, Bd. C., blastodermie cell. Ch., eggshell. G. D., embryonic area. Sep., yolk cleavage plane. Y. B., yolk ball. Plate XXX. Fig.46. Fig. 47. FH. Herrick del. ALPHEUS ” . 524 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. PuaTeE XXXII. Fies. 49-55. Serial transverse sections through 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 (G@. 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, b?°, Figs. 52-54) and their product, 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 amceboid cells with large granular nuclei making their way from the bottom of the pit into the depths of the yolk. Figs. 49, 52-55, x115. Figs. 50, 51, x 291. REFERENCE LETTERS. b, b?-b*, in-wandering cells derived from the invaginate cells and their products. Ch., egg capsule or shell. Ep., ectoblast. G. D., embryonic area. y I. C., invaginate cell. Ig., pit formed by the invagination. 4 Y. B., yolk ball. E > P. Y. C., primary yolk cell. : : Y. S., yolk sphere. : FH. Herrick, del. i Ep:- ALPHEUS —— a ee Plate XXX1. a co oe -_— © ¥ le &e 5S 5 f,) 526 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. ~_ PrArE XOX: Fics. 56, 59, 60. Longitudinal serial sections through the entire embryo in the stage shown in Fig. 58. Fig. 59 is median. The primary yolk cells (P. Y. C., Fig. 60) can still be distin- guished from the wandering cells derived from the invagination (S. Y. C., Fig. 60). In Fig. 59 a primary yolk cell (P. Y. €.') is in the metakinetic stage of division. Traces of the primary 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 (Ch.) is not removed it is seen to be considerably distended and to have epiblastic cells sticking to #t, showing the close adherence which normally exists between the egg membranes and the egg. x115. = Fie. 57. Section through egg, cutting germinal disk just before invagination. Twenty and one- half hours older than yolk-pyramid stage seen in Fig. 15. x75. , . Fic. 58. Surface view of embryo after the appearance of the thoracic-abdominal plate and the optie \ disks. The shallow depression which marked the invaginate area has disappeared. eae,» Its approximate position is indicated by Ig. Compare Jg., Fig. 59. x 291. ; REFERENCE LETTERS. ; Ab, P., ventral plate. 3 Ch., eggshell. Ep., Ep.', ectoderm. G. D., germinal disk. Tg., pit of invagination. L. Cd., lateral ventral bands. O. D., optic disk. sige P. M., wandering cells, seen below surface, coming off from ventral plate. = F ° P. Y. C., P. ¥. C2, primary yolk cells. Sep., yolk cleavage plane. S. Y. C., 8. Y. €.!, wandering cells derived from the invaginate cells and their products. T. Cd., cell area unitiug optie disks. . : Y. B., yolk ball. : a Y. C., primary yolk cell. sx 4 Plate XXXII F’H. Herrick, det ALPHEUS { 4 _ ‘ y ' i ie > es en ae J eee! ee ee Pe See ia Cee | et eee eee Sie 4 i. al Mee ty =o ° UA # Shiny ‘Yist s o Sea ’ - re bt Sead 528 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. __ Puate XXXITI. Fics. 61, 62, 68, 69. Transverse sections of embryo in stage shown in Fig. 58, Pl. xxxu. Fig. 61 cuts the thoracic-abdominal plate, and Figs. 68 and 69 involve the optic disks. Pri- zu mary yolk cells (P. Y. C.. Fig. 69) are still plainly distinguishable. 115. Fic. 63. Portion of median longitudinal section of the same stage. The larger and clearer nuclei 3 in the invaginate area represent the mother cells of both mesoderm and endoderm. % The yolk ball or secondary yolk segment is characteristic of this stage. 291. Fics. 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 Fig. 64. 291. REFERENCE LETERS. Ab. P., ventral plate. Ch., eggshell. Ep., ectoderm. % Ig., invaginate cavity. ae : L. Cd., lateral ventral cord. ay: O. D., optic disk. een P. Y. C., primary yolk cells. Sep., yolk cleavage plane. S. Y. 4, in-wandering cells derived from ventral plate. eS ¥. B., yolk ball. ; ; Plate XXX1II. FH. Herrick, det. “Secket 8 Wiens Labepraphiog Co New Yok ALPHEUS = i aig BNL Swish W ; = Rp biti ie s Hes jee f Ad bee Pe wi , : a # # io oe 530 MEMOIRF OF THE NATIONAL ACADEMY OF SCIENCES. eT. PLatE XXXIV. = MST (Stage IV.) Fias. 70, 71, 73, 74. Longitudinal serial sections of the entire embryo in the stage shown in Fig. 72. In Fig. 73 the plane 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. 115. 7 Fic. 72. Surface view of embryoin Stage rv. Rudiments of the mandibles and first pair of antenne are present. An area of cell ingrowth in the optie disks (C. M.) is characterized by the large size of the nuclei. From them and their products the optic ganglion takes its origin. Some of the surface cells on either side of the middle line were acciden- tally cut away. x291. — - REFERENCE LETTERS. og A. (J.), proliferating center of first antenna. Ab, P., ventral plate. / C. M., proliferating area of optic disk. _Ep., ectoderm. ase 2 L. @d., lateral ventral cord. = Ma., proliferating center of mandible. 0. D., optie disk. T. Cd., transverse cord uniting optic disks. Y. B., yolk ball. Y. C.,-Y. C.', wandering cells. : . - Plate XXXIV. Fig. 14. fi ‘ fe bine iyi ‘ i “dy Beer. NX FH Herrick, del. ALPHEUS. ae an / ‘ v ha ES 5 Ms a F ‘ ° en Ti TES ‘ é nt boZ MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. | : | Zs Puate XXXYV. (Stage IV.) er ¥ p Fic. 75. Median longitudinal section of the entire embryo. One of the wandering cells, whieh is se approaching the surface of the egg opposite the thoracic abdominal plate, is in the ey process of division. 115. Fias. 76-83. Consecutive serial transverse sections through the left optic disk of same, to illus- oa trate the earliest stages in the thickening of the disks. The most posterior section a iy (Fig. 83) cuts the first pair of antenne. x 291. Steet is Fic. 84. Transverse section through the middle of optic disks. x 115. eee el Fig, 85. Transverse section through thoracic abdominal plate, showing the multiplication of sur- be 4 ‘ a face cells, by which the plate is increased, and cells below the surface (Y. C.) which — ae. ie P pass into the yolk. x 291. ry td, : 7 ae om " REFERENCE LETTERS. er = ; A. (1), first antenna. - f We Beets Ab. P., ventral plate. F tre Rae “ie < “ Ch., eggshell. : sm C. M., proliferating area of optic disk. 2 Ss. ec., ec. 8, ectodermic cells of ventral plate (Fig. 85). ec., (Fig. 80) ectodermic cell of optic disk. Se ; : Ep., ectoderm. : + ee: - y x 0. D., O. D\., optic disks. : ; és = ~ Ret , protoplasmic reticulum. ; T. Cd., transverse cord. . = Y. B., yolk ball. fe 5 Y. C., ¥. C.-, wandering cells. Y. S., yolk sphere. etre ty pre & 5 iid as = te Bote 7 = "y 4 ». ae Hlate XXXV. YC eee (0D: Fig.84) ec. wh J Fol FH. Herrick, del. schol ie ALPHEUS ee eae. ite Aiiriee” GA" eee - jm crate Sry, ee pet eS ee ferns f Sr eis , Bee anes Cee ey 534. MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. | Puatr XXXVI. (Stage VY.) Fis. 86, 87. Parts of longitudinal sections of embryo seven or eight hours older than that shown in Fig. 72. The optie disk (0. D.) is cut in Fig. 86, and in Fig. 87 its inner part is involved, with the outer border of the thoracic abdominal plate. There is no sharp demarcation between the protoplasm and the yolk, as is indicated by the dotted lines — under the embryonic layers: x 291. Fires. 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 ae in Fig. 90 through its central proliferating area (C. M.), and the rudiments of ae three naupliar appendages appear in Fig. 89. x 115. Fic. 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 Tigs. 86, 87. Wandering Fy cells ( Y. C.') have traveled to remote parts of the surface, and earyokineae figures Se (Y. C2, Fig. 89) prove that they are in active division, 115. REFERENCE LETTERS. A. (1), rudiment of first antenna. A, (IT), rudiment of second antenna. Ab. P., ventral plate. * App., area of appendages. Ch., eggshell. C. M., proliferating area of optic disk. ec., Migrating ectoblast cell. Ep., ectoderm. Md., rudiment of mandible. O. D., optic disk. S., product of degenerating chromatin. St. 4., sternal area. es T. Cd., transverse cord. Y. C., Y. C.!-, wandering cells. Y. S., yolk sphere. Plate XXXVI FH. Herrick, del. acon W dsinn LAbegrebing Ca Be ALPHEUS ar ay nS oe g Be eth a eR: Scale at Es Ee ig 2 j a4. oF - ph Ss 3 . Aran Md * is yg ws . 5 : 4% " 536 ‘ MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. . + 2 Pirate XXXVI. (Stages V-VI.) ae Fie. 92. Part of transverse section, showing the structure of the keel-shaped ventral plate, and : indicating the origin of mesoblast from the surface of the latter. x.291. Fie. 93. Surface view of embryo with buds of naupliar appendages. The sateen area (St. A.) is covered by a single layer of ectoderm. The invagination of the mouth has not 2 se yet appeared. Some nuclei of cells which lie immediately below the surface, especially hee in the thoracic abdominal plate region, are represented. x 291. ; ‘ hae, ag Fias. 94-95. 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.', s.2, rae Fig. 95) are present, aud two cells are seen delaminating side by side in Fig. 95. REFERENCE LETTERS. A, (1), rudiment of first antenna. A, (IT), rudiment of second antenna. 2 Ab. P., ventral plate. , 5 a C, M., proliferating area of optie Eanglion: Eet., ectoderm. “A saat j { Md., rudiment of faanazbie c Mea wandering cells (mesoblast) attached to ectoderm. 4 0. G., rudiment of optic ganglion. 0. D., optic disk. s.', 8.2, products of degenerating chromatin. St. A,, sternal area. 7. Cd., transverse cord uniting optic disks. ¥. C., wandering cell; Y. C.', wandering cell degenerating. Platé XXXVII. FH. Herrick, del. ck 8 Wine Langage Ye ALPHEUS “Se ut b Foal Ra G MUS eT hee, ( Pay ftp eviw Sw “* FS Be Pana, ie ae 6 : S 7 ie oi = q F . 2 Bee =F \ : SBE OED i 8 =e 4 at ne Se =aee i ; ‘ ao 538 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. | = Prats XXXVIIL (Stage VI.) Fries. 96-97. Longitudinal sections through the embryo shown in, Fig. 93. The more lateral of the two, Tig. 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.). 295. Fras. 98-100. 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 optic disk is in the act of delami- nating. Large numbers of degenerating cells and their products are now encountered (S. C., s.). 295. REFERENCE LETTERS. A, (I), bud of first antenna. A, (IT), bud of second antenna. Ab., Ab. P., Ad. P., ventral plate. App., area of appendages. C, M., proliferating area of optic disk. ¥ ee., ec.', migrating aud dividing cells at surface of ventral plate. Eet., Ep., ectoderm. Md., rudiment of mandible. Mes., mesoderm. O. C., optic ganglion. O. D., optic disk. s., 8, products of degenerating chromatin. S. C., S. C..~, cells in various stages of degeneration. St. A., sternal area. Std., stomodeum. T. Cd., Transverse sheet of ectoderm uniting optic disks. Y., Y. S., yolk spheres. Plate XXXVIZ. FH. Herrick del. ALPHEUS ware Ne a So a | ; ma f _ 7 _ — 7 Ju Sr ed ] Q = ee. . Nageayey A> igi hoe 540 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Puate XXXIX. (Stage VI.) Fras. 101-105. Serial longitudinal sections of early nauplius embryo, twelve and one-half hours older than that represented by Figs. 98-100, Pl. xxxvul, and eighteen and one-half hours older than the stage represented in Fig. 93, Pl. xxxvul. The thoracico-abdomi- nal fold or papilla is now forming, apparently by the ingrowth of the surface ectoblast (Fig. 104, Ab. O.). Fig. 102 is exceptionally favorable in showing the undoubted 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 stomodzeum. x 295. Fic. 106. Longitudinal median section of embryo several hours older than the last. A deep, narrow, transverse furrow (Ab. C.) now abruptly separates the thoracico-abdominal papilla from the sternal area lying between it and the stomodzeum. x291. ~ Fic. 107. Transverse section through the optic disks, from same stage. Cell delamination in this region is again met with. x291. Fra. 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 molted membrane is present, as is better shown in Fig. 106 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. 115. REFERENCE LETTERS. A, (J), bud of first antenna. A. (IT), bud of second antenna. Ab., thoracico-abdominal papilla. Ab. C., transverse superficial furrow by which fold of the thoracico-abdominal process is formed. A. Y. S., products of degenerating chromatin, B, Z., budding zone. Ch., eggshell. C. M., proliferating area of optic disk. : Ct. S., cells on ventral side of yolk next to optic disks, probably representing mesoblast derived from wandering cells. ee., ec.1, dividing ectoblastic cells. Eet., Ep., ectoderm. M., wandering cell at surface behind thoracico-abdominal fold (Fig. 108). Mb., embryonic molt. , Md., rudiment of mandible. Mes., mesoblast. O. D., optic disk. O. G., optie ganglion. O. S. G., brain. Pd., proctodxum. S., S..-°, products of degenerating chromatin. S. C., degenerating cells. St. A., sternal area. Std., stomodeum. Y., Y. S., yolk. ) Plate XXXIX. FH. Herrick, del. asso Wise ibagagtang (ore ALPHEUS '¢ Ko ~ 542 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Prats: XL: Boe (Stage V1.) : = ‘ Fie. 109. Sketch of egg-nauplius. Anus not so clearly seen in surface view, as represented 21) Te Pp this and the following figure. Mouth on a level with antennules. x72. =o} Fic. 110. Sketch of older embryo. Appendages all bending backwards and inwards toward | middle line.” x72. ; Fia. 111. Egg-nauplius less developed than shown in Fig. 109, but from same batch of eggs. The position of the mouth, which is post-antennal from the first, is now on the middle — line between the antenn# and the antennules. 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. 157. | : Fig. 112. Oblique transverse section, through egg-nauplius of a common shore érab of Beantort, North Carolina, probably Sesarma. x 286. . 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 (Y. C.), and in Fig. 113 degenerative products (Deg.) are met with. x 286. é REFERENCE LETTERS. A,, anus, A, (J), antennal bud. 5 Z A, (1), antennular bud. . : a Ab., thoracico-abdominal fold. t F Ch., eggshell. F : : By: ke : Deg., degenerative cell products. = ‘ Ep., ectoderm. 3 fee. Gl., ectoblast of neural plate. wale : : : H,, mesoblast cells, forming rudimentary heart. — > & E Hg., hind gut. ae . Lb., labrum. ; 9 Md., mandibular bud. Mes., mesoblast below surface, . 2 ais O. G., optic ganglion, : , O, L., optic lobe. . ane: ee 0.8. G., 8. O, G., rudimentary brain. $e ike ? Std., stomodeum. : mS nek Vac., vacuole. ua Y. C., wandering cells. ‘ Numbers 114-125 mark the planes of the transverse and longitudinal sections represented on Pls. A, XLI-XLIII. ; : Plate XL Fig.110. --- Mes. r “orssn., Mt( 1). FH. Herrick, del. ALPHEUS AND SESARMA? a Ble KO's gf 4 lev aad 544 Fries. 114-118. Transverse serial sections of egg-pauplius in stage shown in Fig. 109. Plane of s a ae MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. *y ane -PratE Gk = (Stage VL) I “ section indicated in Fig. 111, 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 delaminating cell (ec.) at the surface of the optic lobe is cut, andin Fig. 115 a superficial ectodermic cell next the brain is dividing perpendicularly. Ge Ss 4 intimate fusion of the brain and the optic ganglion is seen in Figs. 115, 116. Fig. aon 117 cuts the stomodeum passing through the mouth and the antennze. Mesoblast is — already well established in the pockets of all the appendages, as indicated at an earlier period. Degencrating cell products (S., A. Y. S., Fig. 18) are very abundant oho ies in the region of the stomodeum, and oceur also in the appendages (S.-8.!, 8S. C., Fig. an 118). «291. : a REFERENCE LETPERS. A, (J), antennal bud. a . ‘ a) A, (ID), antennular bud. A. Y.S., alteration products of yolk. xe wy 7 Ct. S., cells partially covering brain, derivatives from yolk-wandering eells, ec., surface cell of ectoderm dividing horizontally. ; Ect., Ep., ectoderm. Md., mandibular bud. Md. G,, mandibular ganglion. © M. F., median furrow. 0. G., optic ganglion, — O. L., optic lobe. Ret., protoplasmic reticulum. S.S.!, products of cell degeneration, 8. O. G., brain. Sid., stomodzum. Vac , vacuole. Y., ¥. C.,-yolk. > ‘I F-H. Herrick, del. Fig 118. ALPHEUS SAULCY!. Plate XZ 546 Fies. 119-1 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 4 Piare XLII. | (Stage VI.) | ee 22. Serial transverse sections of the egg-nauplius, continued from Pl. xu1. 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, mu.) the abdominal muscles are already undergoing differentiation Se out of the mesoblast of the ventral plate. 295. 7S Ab., abdomen. _ : me. A. Y.S., yolk undergoing change. ; B.Z., budding zone. : : Fem, Det., ectoderm, — = y 0 pe aa Hq., intestine. Pe Sl Md., mandible. aS ae Ma. G., mandibular ganglion, ; eS ake Mes., mesoderm, 2 : : pias : M. F., median groove. . mo Mu., muscle cells. ee te Mz. (1), first maxillary bud. ; re s.', products of cell degeneration. = tes S. C., degenerating cells. Y., yolk. ¥.C., Y. €.', wandering cells. Vac., vacuole. Plate XLIT E\H1. Herrick, del. sect 8 Wlaeions Lathapraphung Ca New York ALPHEUS SAULCYI!. ae ee Ses es ee ee ee. ae Pale ta Puare XLII. = (Stage VI.) -. Fias. 123, 124. Completion of series of transverse sections of egg-nauplius. Cells marked Mes. probably represent endoderm in Fig. 124.. The heart is being formed at about this time out of mesoblast cells at H, Fig. XL, and the endoderm ee a plate between it and the central yolk (v, lig. 133). x 295. Fie. 125. Median longitudinal seetion aes same stage. Compare with Fig. 106. The thoracico- | abdominal fold is now distinctly directed forward, ani is overgrowing the sternal area between it and the mouth. The stomodzum isa bent tube. x 295. Fic. 126. Transverse section, cutting proctodeum. From an embryo of about the same age as that represented in Fig. 106. 295. = Fig. 127. Transverse section of embryo and entire egg on level with anus, ahowiee wandering cells (Y¥. C., ¥. Or i) soba rams a REFERENCE LETTERS. : ; Ee A., anal invagination. : Ab., abdomen. -* A.Y.S., altered food yolk. : Ch., eggshell. _ - : d ‘ Pax ; Ect., Ep., ectoderm. ; ; 4 ; eae: Gl., ganglionic rudiment. E : ; H., rudiment of heart. : sa Hg., intestine. ; ; ; Lb., labrum, . ; 3 z Mb., embryonic molt. Mes., mesoderm. : - My Mo., mouth. : ae x ; Pd., region of proctodwal invagination. Shey Fea 8.,8!., products of cell degeneration. a s. C., wandering cells, probably in early stages of degeneration, S. 0. G. , rudiment of brain. St. A., Ciortal area. > Std., stomodzeum. : VAS aos Y.C., Y. C2, wandering cells. ¥Y.8., yolk spherules. — Vac., vacuole, Fig. 125, FE: H. Herrick, del. ALPHEUS SAULCYI Plate XLUI det: & Widnes Ladhoprmsticng Co Seow Vth Pratt XLIV. oe é (Stage VII.) Fra, 128. Transverse section through embryo, in the region of the first maxilla. Nervous system not yet differentiated from the skin. x 234. . Iria. 129, Lateral longitudinal section through optic lobe and extremities of antenne. The differ- entiation between the retinal and ganglionic parts of the eye is very clear. Meso- blastic cells, representing rudimentary muscles, are seen attached to the body wall. x 234. Fic. 130. Surface view of embryo of this Stage, with buds of four post-mandibular appendages present. The antennz are covered with a hairy exuvium, which was probably stripped off from the antennules 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 emarginated. 137. fia. 131. Median longitudinal section in the series from which Fig. 129 was taken. x 234. Fries. 132-135. Serial transverse sections through embryo in similar Stage. The germinal layers, definitely established in the egg-nauplius stage, are clearly differentiated at this period. An incomplete layer of elongated cells (probably mesoblastie in origin, com- ing from wandering yolk cells), Mes., Figs. 131, 132, is seen between the yolk and the neural thickening, trom which the nervous system is in process of development. In Fig. 134 rudimentary muscles suspend the stomodzum 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 serum, between the entoblastic lamella and the ectoblast. x 234, . REFERENCE LETTERS. A.J, first antenna. A. IT, second antenna. Ab., thoracico-abdominal fold. A. Y.S., alteration products of the yolk. Ect., ectoderm. End., endoderm, G. L., rudiment of optic ganglion. Gl. 4. II, antennular ganglion. Lb., labrum. Mes., mesoderm. Mo., mouth. Mu., rudimentary muscles. Mx. I, first maxillary bud. 0. E., retinal portion of optie lobe. S. 0. G., brain, Std., stomodzeum. Plate XLIV. F: H.. Herrick, del. Sack et & WDetms Labaprgtang Co Merwe Tort ALPHEUS ms < a= AG a i eae ae ‘a J ; 552 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. ; ¥ PLATE-XLV. . (Stage VIII.) od Fie. 136. Lateral longitudinal section of embryo in stage intermediate between VII and VIII, represented in surface view in Fig. 110. To this phase also belong Figs. 137, 144, and 145, Fig. 136 is to be compared with the slightly older embryo in Fig. 129. Blood cells (. C.) and other wandering cells are here seen settling down upon the body wall. A wandering cellis also seen nearly in contact with the optic ganglion. x 241. Fig. 137. Transverse section of embryo in same phase, just behind the level of the first antennz, 4 showing the relations of the wandering cells at this period to the embryo and egg. x 61. i Figs. 138, 139. Serial longitudinal sections through embryo in Stage VIII. Fig. 138 should be compared with Figs, 136 and 129. All the ganglia of the nervous system, at least as far back as the eighteenth segment, are marked at the surface by deep constric- tions. The gangliaof the nineteenth and twentieth segments are less distinct. The ganglia of the eleventh segment lie in the angle made by the thoracico-abdominal 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. "241, : Fies. 140-143, 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 réle of certain wandering cells which reach the surface and represent mesoblast. In Fig. 140 two cells (ms., ms.') are partially flattened against the surface, but here, as in Fig. 142, the wandering cell ms. is clearly distinguishable trom the spindle-shaped ectoderm cell on the left. Compare Fig. 34. x 241. Fias. 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 (Dp.)—which is characteristic of a later stage (Fig. 153, Dp.). The strictly superficial cells of the dorsal plate are probably 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 thoracico-abdominal fold. The wandering cells which appear in this part were taken from four consecutive sections, including that represented in the drawing. x61, REFERENCE LETTERS. A. TJ, first antenna. A. II, second antenna. an., lower margin of optic lobe. A. 8. a., Superior abdominal artery. B. C., blood corpuscle. b.m., basement membrane. ch., eggshell. Dp., dorsal plate. End., endoderm. G, IV-XVIII, segmertal ganglia. Gl., gangliogen, H., heart. hd., hypodermis. Hg., hindgut. mes., mesoblast. mo., mouth. ms., ms.', wandering cells at surface. 0. L., optic lobe. Rt., retinogen. Std., stomodeum. Th. ab., thoracic-abdominal fold, y.c., wandering cells, Plate XLV. NS Daw F-H. Herrick, ded Sac a1 8 Withee ghng Ue few Yar ALPHEUS ; iin 554 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES, _ : Puate XLVI. (Stage LX.) Fias. 146-151. Serial transverse sections, through the embryo ot A. sauleyi, at the time when pigment is first deposited in the eye. In Fig. 146 the developmental history of the retinal layer is well shown. x 230. Fia. 152. Nearly median longitudinal section of embryo in similar stage. x48. Fig. 153. Sagittal section of similar embryo, showing degenerating elements in yolk below dorsal plate. x58. REFERENCE LETTERS, A.J, first antenna. A. IT, second antenna. Ab., abdomen. B. C., blood corpuscle. B.S., blood space. cp., carapace, Deg., degenerating cells. - Dp., dorsal plate. End., endoderm. Sfy., foregut. fs., fiber mass of nervous system. g. II-III, brain. g.¢., ganglion cell. g.m.a., anterior gastric muscle. H., heart. hd., hypodermis. Hy., hindgut. Lb., labrum. Md., mandible. Mes., mesoblast. Mu. f., flexor muscle. ocm., esophageal commissure. 0.g., optic ganglion, 0. L., optic lobe. pk., punct substanz. pr., perineurium. Kt., retinogen. S. 0. G., supra-wsophageal ganglion. ’ T., telson. 3 Tc., transverse commissure. Th., thorax. Vac., vacuole. y., yolk, ¥.C., wandering cells. dhe Plate XVI. F-#f Herrick, det. ALPHEUS 556 MEMOIRS OF THE NATIONAL Puate XLVII. a = ee (Stage IX.) 5 Pate Pies, 154, 155. Transverse sections through entire embryo of Alpheus saulcyi. In Fig. 154 a yolk oar ¥ nest is cut. Blood spaces occur near the surface of the egg. x61. 2 Si Fic, 156. Cell nest, containing degeneration products. Its position in the yolk is shown in Fig. : 5 154. x 245. pe Fie. 157. Part of median longitudinal section through the thoracic-abdominal flexure. The grow- : ake ing endodermal epithelium and its fusion with the lining of the intestine are particu. Bary larly well shown. Wandering cells appear to be uniting with the endoderm. »x245. Fic. 158. Sketch of egg embryo, Alpheus saulcyi, of same phase as that represented by Fig. 157. x 61. " ; g Fic. 159. Horizontal section through brain and eyestalks of a slightly older embryo. x61. Hg., hindgut. imb., intercepting membrane, mg., Mesenteron. mo., mouth. mpgT, first maxillipedal ganglion. Mu. E., extensor muscles, Mu. f., flexor muscles. O. G., optic ganglia. p.8., pericardial sinus. Rt., retinogen. S. O. G., supra-cesophageal ganglion. T., telson. Th., thorax. ; M Th. g. I, ganglion of first ambulatory limb. y-¢., wandering cells. Plate XLVI ‘ en é . (d Eo, \S ( V g) = 5 ry) CU a. G Ow NC YQ F-H. Herrick, del ALPHEUS mere ; : att fA ‘MEMOIRS OF THE NATIONAL ACADEMY or ‘ot Puate XLIX. ahs ie aa. _ (Stages X and XIL) ie ea a ; - Se Figs. 169-173. Parts of serial transverse aéetions through the embryo of Alpheus Sint: in Stage X. In Fig. 173 the reproductive organ KR. O. is cut. x129, (Fig. 173, x 234.) my : Vic. 174. Horizontal section through nervous system of the first larva, on a level with the eaaphaee eae geal commissures. 234. > “= Vias. 175, 176. Transverse sections through the neural cord of the first larva. In Fig. 176 th ans transverse commissure of the ganglie of the tenth segment is eut aud aim ne es 9% aes sectioned. x129. | : >, REFERENCE LETTERS. “ = . AT, first antenna, - aN : : : 2 A. II, second antenna, = aie ‘ b., abdomen. + ee —_ag., antennal gland. : . : \ B.c., blood corpuscles, 3 ers: —B.S., blood sinus. : s eye. aks Br., branebia. cp., carapace. : vite aye Se End., endoderm. : ; JS hig pee Jq., foregut. z j , oo ; g.¢., ganglion cell. y . — PRON eee! AAR ee Had., hy podermis. Y : aA ss as hindgut. , an Ces 1. f., lateral fiber-mass of, brain. a ign Md., vase of mandible. < Sees et Mes., mesoderm. z Bes be te aed Mg., wesenteron. . : FROME Sav oh LP Mu., muscle. xs : Mu.e., extensor muscles of abdomen. — en : - Mu.f., flexor muscles of abdomen. =, Zz bs ane Mzx., base of maxilla. . , ; pes Muepd., base of maxillipeds. ; af V4 -g re n.c., neural cord, . a of., optic fiber-mass of brain. 0.9., optic ganglion, Pr., perinearium. bat, ete k, O., reproductive organ. : Ee Sic Sie 80g.) DEIN. se : and pasa Hat t.c., transverse commissure, ; x eee: y.c., Wandering cells, : ee Pa Plate XLIX. FH. Herrick, del. ALPHEUS MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. — | Prare =; s (Stage XL.) , 1 ate as Fes. 177-179, 181, 182. Serial transverse sections of the embryo of Alpheus heterochelis, whieh i is nearly ready to hatch. The shell is somewhat diagramatically represented and appears = thickened in Fig. 182, owing to a coagulable substance beneath it. The cells rep- resented in the yolk in Fig. 182 appear to be endoderm cells, which have become 2 mechanically detached from the walls of the mesenteron. x 74. e Fic. 180. Nearly median longitudinval section through a similar embryo. The endodermal lining = ri: of the mesenteron is not yet nearly completed. x 74. f s i : REFERENCE LEWTERS. : Ae Ab., Vi, ganglion of sixth abdominal appendage. ag., antennal ganglion, ans., anus. = ch, ex., external ene f ect., Sctiee 7 end., endoderin, ‘ ; he JSq., foregut. : ; BE Xn 2 gma., anterior gastric muscle, =i: ‘ H., heart. ; Pa Si SE eae hg., hindgut. 3 : , rian goog he's hy., Ly podermis. ~ Se yd ey 1f., lateral fiber-mass of brain. \ Fy, hoe mg., mesenteron. + Sw ye, mg.! mg? of other figures, posterior lobe of midgut. ‘ ; ; ear mu. f., flexor muscles of midgut, pine mu. é., extensor muscles of midgut. Per eee ; meee ~ oem., esophageal commissure. ‘ ss 4 o. pd., optie peduncle, ; ; 4 . * Ret., retina. soq., brain. > : ss T., telson. : ease, 08 gat 1-4, ganglia of eye-stalk. . Plate L.. FH. Herrick, del. 2.01 8 Wtaetns Labographeng Ce. Mew York ALPHEUS HETEROCHELIS. Phare. Bs? ee eae oe ee : | aes (Stage XI.) j epee) ory, Figs. 183-186. Continuation of series of transverse sections of embryo beeun on Plate ve x4 Fic. 187. Part of sagittal section of similar embryo, cutting eyestalk somewhat obliquely. Th / specimen was depigmented in nitric acid. The distal retinular cells, occupying the _ * spaces (P9.c.) between the peripheral ends of the cones, are not represented. x 305. Pork REFERENCE LETTERS. \- Ae ei ~ ac. P., accessory pigment cells. a “! ye eh ad.m., adductor of mandible. ‘ aL ‘ Cnty ey a. 80., eee abdominal arter y- MG q é > bg., branchiostegite. “ ; = ~ b.v., blood vessel. : Pay ce (ees crystalline cone. : 1 ara eg., corneagen. , “es, ORE ect., ectoderm. | LAr) ey 4 end., endoderm. — : saan Say iat sa Sat \ ; : f9-, foregut. : bod Sa ee ed 1 R #., heart. : ey et eS ee A hy., hypodermis. : 3 imb., intercepting membrane. ‘ ea Sets mg., midgut. es | : Mice ees ing.®, posterior lobe of midgut. g : fee Mu., muscle of eyestalk. = ' 4 poe Mu. e., extensor muscles of abdomen, Mu. f., flexor muscles of abdomen. Si SAN Alnor 0.¢.m., esophageal commissure. = ee i : Pq. C., position of distal retinular cells. etek Ps., pericardial sinus. ie cet Rtu., proximal retinular cells. Oy Mer, : Rtu.', nuclei of proximal retinular cells. Seg e 3, 4, ganglia of eyestalk. (ft 2 i * Ped ee ee a Se Plate LI. Sachets 8 Wilber Ltbegrapneng Co. Mew York FH. Herrick, del. ALPHEUS - ie MEMOIRS OF THE NATIC NAL ACADEMY OF = if ‘ ia PLATE Tse a2 Fias. 188, 189. Parts of transverse serial sections front the embryo of Baleannates vulgaris, 2 a +e. _ the stage when pigment is just appearing in the eyes. In the anterior Bestion (Fig. 188) the retinogen is a unicellular layer. 305. = rahe Fias. 190-191. Parts of serial transverse sections through the brain, the optic ganglia, : and eye. of." an embryo of Alpheus heterochelis. In the anterior section (Fig. 190) the clusters (8) nef cells which represent the ommatidia are well shown. Numerous eaneuee cells are ace dividing. x305. : =. aa tales Fic. 192. Part of transverse section through eye, optic ganglion, and brain at a later stage x 305, — REFERENCE LETTERS. : ‘ é Pits hehe A.J, first antenna. : iy Ab., abdomen. : cae i Phy a's ce., erystalline cone cells, ; : : imb., intercepting membrane, ‘ “. mes., mesoderm. Paty ee Ret., retina. é ‘ TEN rtl.’, rudimentary eighth proximal retinular cell, 8og., brain. T., telson, “ ' re X., stratum of large ganglion cells. ; : t 1, 5, 4, proximal, external mda and distal peenenia of optic ganglion, ; Plate LI. Fig. 189. AL GpVORG a. AU \ pee, FH. Herrick, del. ALPHEUS AND PALAEMONETES. Pe | TA ee ay et — v 568 Fic. 193. Fia. 194. Fie. 195. Fic. 196. Fie. 197. Fie. 198. Fie. 199. MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. Prats LET Part of transverse section through an embryo of Alpheus sauleyi, which is nearly ready to hatch, showing the third left branchia covered by the branchiostegite. x 289. Part of sagittal section of eyestalk of a slightly younger embryo. x 289. Part of transverse section, showing branchia, of the third larva of Alpheus sauleyi (twenty- four hours old). x 289. £ Nearly median longitudinal section of first larva of same. The anterior lobes of the midgut (mg') still contain unabsorbed yolk. Compare Pl. xxi, Fig.1. x58. Part of transverse section, showing the papilla, which bears the median eye in the first larva of same. x 289. Transverse section of first larva, cutting the lateral fiber balls of the brain, the anterior lobes of the midgut, and the green gland. x 289. Part of transverse section through an advanced embryo of Alpheus sauleyi, parasitized by a fungus, most of the cells of which are encysted. From brown sponge, Abaco, Bahama Islands. v, Appendix II. x 186. ab., abdomen. Ab, VI, sixth abdominal appendage. acp., accessory pigment cells. ag., green gland. ag.s., end sac (?) of gland. as. d., Superior abdominal aorta. bg., branchiostegite. b. s., B.S., blood space. br., branchia of third left ambulatory limb. ce., crystalline cone cells. eq., corneagen. el,, lens. co., crystalline cone. cs., c8.‘~, cysts of parasite. es.°, smaller, naked cells of parasite. g.+°, segmental ganglia. gf., tiber-mass of second antenn:e. gma., anterior gastric muscle. H., heart. Hd., hy podermis. Hg., hindgut. Lb., labrum. l.c., longitudinal commissure, mg., midgut. REFERENCE LETTERS. mg.', anterior lobes of midgut. mg.*, lateral lobes of midgut. mg.*, posterior lobes of midgut. mo., mouth, ms., masticatory stomach. mu. é., extensor muscles of abdomen. mu. f., flexor muscles of abdomen. n.¢., neural cord. oc., ocellus, oe., esophagus. O.G., 0.g., optic ganglion. of., optic enlargement of brain. op., ophthalmic artery. ps., pericardial sinus. pr., perineurium, f., rostrum. Ret., retina. rtl., nucleus of proximal retinular cell. sog., brain. Sp., parasitic growth. St. s., sternal blood sinus. T., telson. y., yolk. Plate Lil FH. Herrick det. ALPHEUS Puate LIV. Fic. 200. Ommatidium of eye of small adult Alpheus Sea (from brown sponge) ; pigment. removed | by nitric acid. x 294. “ Fics. 201-204. Transverse sections through four wajacant ommatidia of first eae ofsame. In Fig. 201 the corneagen is cut, and in Fig. 202 the nuclei of the cone mother cells. In Fig. “204 the rhabdom is sectioned and the seven proximal retinular cells. 294. | Fias. 205-208. Transverse sections through adjacent ommatidia of the adult eye, taken at various levels. Fig. 205, the deepest section, shows the peculiar seven-pronged figure of the rhabdom. The proximal retinular cells appear in sections, asif fused together. x 294. Fies, 209-211, Transverse serial sections through the first larva of Alpheus saulcyi. x74. REFERENCE LETTERS. A. TI, first antenna. A, II, second antenna. a. cp., accessory pigment cell. ac.pn., nucleus of accessory pigment cell. ao., ear. Bm., intercepting or basement membrane. ce., crystalline cone cells. ¢g., corneagen. el., lens. Co., co., crystalline cone. emb., cone membrane. hd., hypodermis. me., membrane of distal retinular cells. nf., nerve fibers. oc., ocellus, og., optie ganglion. of., optic enlargement of brain. pap., papilla of ocellus. p.g.¢., distal retinular cells. X., rostrum. Rb., rb., rhabdom. Ret., retina, rtl., proximal retinular cells. Plate LIV. F-H1. Herrick, det. Sect d Wikchanegryting Ca Rew Te ALPHEUS ; . bN Rat MEMOIRS OF THE NATIONAL ACADEMY OF od PLATE: GV " oor pes : (Stage XI1.) seers ; oie Fics. 212-223. Transverse serial sections of the first larva of Alpheus sauleyi from Joes same indi- vidual as Figs, 209-211, excepting Figs. 222, 223.- shag REFERENCE LETTERS. ; pean es A. II, second antenna. - oe PoRe j ‘ ad. m., adductor of mandible. ee ' - ag., green gland. : Eres aon af., antennular fiber- -mass of brain. 4 a ao., ear. ‘ sees Wy 2) Te ; a. op., ophthalmic artery. : , ; yrs Bg., branchiostegite. ~ : i: ”; B.gl., gland-like body. — OA ce 4 B.S., blood sinus. - 2 ae ; Pic atlea ant Sy., foregut. ; 3 ah SA ge oii ae te So., fiber-mass continued into esophageal commissure. 2 eee a gf., antennal fiber-mass. 3 gs., lateral pouch of masticatory stomach, ‘ and Lb., labrum. x ; = Agee lf., lateral fiber-mass of brain. a Md., mandible. ~ Mg., midgut. Mgq'., anterior lobe of midgut. er Mg?.. lateral lobe of midgut. 5 Mp., septum between anterior lobes of midgut, ‘ = nase M.S., masticatory stomach. Mts., metastoma. Me. T, first maxilla. Mupd. I, first maxilliped. n. ag., antennal nerve. : nose n.an., antennular nerve. 0c., ocm., «esophageal commissure. of., anterior fiber-mass and transverse commissure of brain. p. V., pyloric valve of masticatory stomach. — st. s., sternal sinus. ‘ Plate LV F-H. Herrick, del. FIRST LARVA OF ALPHEUS SAULCY!. ov MEMOIRS ov THE NATIONAL Ac EM OF Prate LVI. (Stage XI. My REFERENCE LETTERS. Ab. V, fifth abdominal appendage. a.i.a., inferior abdominal aorta. a. op., ophthalmie artery. ~ a, 8, @., Superior abdominal artery. bg., branchiostegite. br., branchia of ambulatory appendage. B.S., blood sinus. gg. ©, middle, ventral, and dorsal lobules of posterior lobe of midgut. 25 Be hear ‘ hg., hindgut. hy., hypodermis. R le. th.-ab., longitudinal commissures uniting last tee with first abdominal ganglia. a 3 _ Mq., midgut. is Mg. *, lateral lobe of midgut. Mq.*, posterior lobe of midgut. Ms., masticatory stomach. Mu.e., extensor muscles of abdomen. Mu, f., tlexor muscles of abdomen. Mrpd. I-III, first to third maxillipeds, pleu., pleuron. ps., pericardial sinus, Th. I-V, tirst to tifth ambulatory limb. 3 Plate LV1 ala. F:H. Herrick, del. FIRST LARVA OF ALPHEUS SAULCYI. : DP eal by sre Pirate. LVI. (Stage NTL). _ Fias. 236-245. Horizontal sections of first larva, jNoacebag: further the penctomy Be. the limen tary tract and the nervous system. x 57. REFERENCE LETTERS. A.J, 11, first and second antenna. ag.. green gland. af., antennular fiber-mass. a0., ear. bg., branchiostegite. Pnd., endoderm. Jy., foregut. : Jo., fiber-substance of wsophageal commissure, gf., tiber-mass of second antennz. gg-'~*, middle, ventral, and dorsal divisions of pouiesion lobe of midgut. : hg., hindeate : /f., lateral fiber-mass of brain. Md., mandible. Mq., midgut. Mq.', lateral lobe of midgut. Mp., partition between anterior lobes of midgut. Mts., metastoma, Me. I, I, first and second maxille. Mxpd. I-LII, first to third maxillipeds. ‘n.an., antennular nerve. n.¢c., ventral nerve-cord. of., anterior fiber-mass of brain. og., optic ganglion. Ret., retina, t Th. I-V, first to fifth ambulatory limbs, y., yolk. Plate LVI FIRST LARVA OF ALPHEUS SAULCY!. * , : * 4 zy a v : x —— i —— = y ) PE a ea Sone A Fae a So Ayal 7 OF aM ry a an ta fi aati ee Face = aA annem 52 on if ARARA AA Aa aS Aig.) Py aa ALS. 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