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THESIS,

ON THE
ANATOMY AND DEVELOPMENT
0 F
CASSIOPEA XAMACHANA, S£.n.

A THESIS

Presented to the Board of University Studies in the
Johns Hopkins University
For the Degree of Doctor of Philosophy
By
Robert Payne Bigelow, S. B.

Baltimore, April, '1892.

3-^, 2,iO

CONTENTS.

INTRODUCTION
TECHNIQUE
SYSTEMATIC PART

Diagnosis

Comparison with Other Species
GENERAL DESCRIPTION

Form of the Body

Stmcture of the Jelly

Color Markings

Variability of Marginal Sti^ictures

Structure of "arginal Sense Organs

The Oral Arms and their Branches

The Oral Disk

The Subgenital Cavities and the Digestive
Tract

GNrOGEI.^Y

Historical Review

Development of Gassiopea from Buds

Formation of the Bud

II. The Plpaiula-like Larva
III. Formation of tlie iviouth
IV. The Eight Tentacle Stage
V. The Sixteen Tentacle Stage
VI. The Complete Scyphistoma
VII. The Strobila

Development of the Rhopalia
Other Phenomena of Strobilization
VIII. The Ephyrula
IX. The Later Stages

CONCLUDING RMIARKS

LIST OF PAPERS REFERRED TO

EXPLANATION OF THE FIGURES

VITA.

INTRODUCTION
oOo-----

In the Island of Jc-jnaica, at the west side of the mouth of
Kingston Harbor, there is a large pona of salt '.v--.i.er cornpl^bely
separated from the sea by a sana boach, wiach au its narro'/esu
pari is several rods in vyiduh. It is said, ho^^ever, by tliose
who livG near, that in times of storm or freshet this barrier
is sometimes broken through.

One morning in June, 1801, '-'r. (r. W. Field ;vhile hunLing
birds along thb seaward shore of this pond, came upon a little
jbay connected witli it by a narrow inlet. This bay is overhung
by low cashaw ana mangrove trees. At one side is a sunny, sandy
spot, where a crocodile had made its bed and from tiiis there
'was a fresh zigzag mark left by its tail when it last slid in-
to tiie -.'/aver. Upon tht:-. submerged roots of Uie mangroves were
to be founa barnacles and sea anemones, but the most inoerest-
iing thing observed was a collection of beautiful rhizostoma-
'tous mf^ausae, Lhat, at one end of the bay, completely covered
the bottom, to the verj edge of the wauer. A fev very small
specimens mighL be seen swimming about, but most of Lhe medu-
sae, especially the larger ones, would nob leave tne bottom un-
less they were disturbed. They lay thsre upon theii* backs with
-their voluminous, branching mouth pai'ts spread out oYer their

! -.- ^

disks, vviiich were motionlbss except, fo. ocv^asional fl^ips oi'
uheir mai|:ins. If any of ^nesG animals were sbii'red up they
would swim about like ordinary medusae but it would not be longj
before they would settle do\vn again and assuine their usual at-
titude upon the bottom. V'ithin this limited area there were
countless nu.mbers of them., and in m.ary places they were so
thickly spread that their margins touciied upon all sides, or
even overlapped.

In order that tho rest of us mi;-:ht know something of this
marvel, Mr. Field dinped up a numl^er of these medusae in a pail
and brought them into the iviarine Laboratory of the Johns Hop-
kins University, which was stationed at this time at Port Hen-
derson, about two miles away. Upon examination of the me-
dusae they were found to ijelong, all of them, to a single nev/
species of Gassiopea, a ,H^enus not known before outside of the
Red Sea, Indian Ocean and souLh-west Pacific ; and this pail-
ful, taken up at random., contained both adults ai^d youn:; in m;a
ny stages of growth. Of some of these ^rofesso>' brooks m.ade
drawings. Subsequently I visited thb Salt Fond to obtain more
of the youn;'; medusae and witli them I collected at random sub-
merged bits of wood and stems of plants, in the hope of find-
ing scyphistomas. On returning to the Laboratory, I was de-

lighted to find some of these objects thickly beset in places
by the larvae for w}:ich I was looking. I was still more de-
lighted wher: in one of the largest of tliese larvae I noticed |
certain glistening spots in the bases of the tentacles ana
found on exar.iining them with a microscope that these spots
were, as I suspected, unmistakably masses of crystals that
would form parts of future marginal sense organs. After this

discovery, I entered, with the advice of Professor : rooks, in-

t
to an investigation of this i'laterial, th'. results of which are

embodied in the present paper. I wish to express my thanks
to him for his lielp and encourci^'jom.cnt during this work and I
am also indebted to him for su£';^jesting the na,me by which I
propose to call this species. Tt is derived, from Xam.acha, .
which was the name used by the Aborigines for the island that
we now know as Jamaica.

A single "lonstrcus specimen with but two subgenital cavi-
ties, with extraordinarily large oral vesicles, and otherwise
misshapen, that perhaps belongs to this species, was found in
the harbor near "ort Poyal . Except for this doubtful specimen
the only locality in which this species has 'neen found is the
lagoon that I have described. Although the adults and the
young in nearly all stages were present at this place in such

- 3 -

great numbers searches for males and for females with ripe eggs

were equally fruitless. The great abundance of young and the

range in their apparent ages was, therefore, surprising, until

I founa a method of buuding in the scyphistoraas, to be desci-ib-

ed later, which easily accounts for these phenomena.

The full grown medusae could be kept in good condition in
I
iaquaria for a number of days and could be kept alive for weeks,

iwhile the young medusae and scyphistomas woula thrive there an
indefinite time if there was a little pond ooze at the bottom
of the aquarium, and the v;ater was changed twice a day. In-
deed the growth and multiplication of the scyphistomas would
proceed actively under these conditions. Ey keeping the lar-
vae in shallow dishes I was able to watch the whole course of
non-sexual development, but the development from eggs remains
unkno^vn to me because of the impossibility of finding any that
woula develop.

I shall first give a systematic description of the specieS;
with an account of the anatomy of the adult, and follow this
with what I have learned of the development, from observation
of the living animals while in Jamaica, and by study of sec-
tions of the preserved material since my return to Baltimore.

- 4 -

TECHNIQUE.

For preservation of the material I used a one-cjuarter sat-
urated solution of picric acid with 2% of sodium chloride ad-
ded, Erlicki's fluid with the same addition ; end l/^'X osraic
acid followed by Erlicki's fluid. The last two methods pre-
serve external structures and the general shape of the animal
very well, but the first method is much better for internal
structures.

SYSTEM ATICPART.

Cassiopea Xamachana, species nova.
Diagnosis. The umbrella is concave on the aboral side

forming a sucking disk. The number of rhopalia is regularly Kl
but often from 17 to 23. when there are 1(3 rhopalia there are
80 short obtuse lobes in the margin of the umbrella, separated
by deep grooves on the surface of the umbrella (in each of the
16 parameres 3 velar lobes between 2 ocular ones.) The exum-
brella is marked by a white circle at the periphery of the con-
Qavity ; from this there extends outward a white band along
each marginal lobe, and in the radius of each rhopalium there
is also a white band tapering centrally from this circle to a

- 5

ipoint about half way to the stomach. These radiatin?-; bands
are not always connected with the circle of white. The eight
oral arms are roimded and slender, never argular, with 10 to
15 alternate primary branches and numerous secondary ones.
The distance from the centre of the oral disk to the tip of an
extended arm nearly equals the diameter of the umbi-ella. In
the axil of each branch there is a flattened oval or linear
vesicle varying in length with the size of the adjoining branch,
the length of the eight largest ones (one in the axil of the ;
chief branch of each arm) may be one to three centimeters, but
many do not exceed the size of one of the oral funnt-ls. There
are also 5 to 13 large vesicl'-s on the oral disk, the one in
the centre being the longest, sometimes equalling l/4 the di-
ameter of the umbrella. L. full gro'vn individuals there
are no oscula, or oral ■ .jinels, on the oral disk, except near
its margin. Their place is taken by a great number of vei'y
:es.

Comparison with Other Species.
This species is very similar to Cassiopea Andromeda. Esch.
and to C. polypoides^Keller. It differs from the first as
described and figured by Tilesius, in the shape of the umbrel-
la ; in having' much longer and stouter oral arms, with ten or

more primary branches that are never triangular in section ; in
having much larger oral vesicles ; and never anything corres-
ponding to the flattened condition of the ultimate branches
figured by Tilesius and mentioned by Haeckel. T-he arrange-
ment of the white spots and other color markings is also some-
what different. It is distinguished from the second by hav-
ing fewer of the large oral vesicles and having these of a
smaller size ; by having more slender and graceful oral arms
than those figured b;- Keller, with a greater number of primary
jbranches ; and by a difference in the coloration.

It is readily distinguished from G. omata, Haeckel, by
its large oral vesicles and from C. .MerLensi, Brandt, G. de-
pressa, Haeckel, and G. picte, Vanhoffen, by the number of mar-

ginal lobes.

GENEPAL DESCRIPTION.

Form _qf the Body.
To one who has only seen the Gyaneas, Aurelias, and the
like, of our northern coast, the shape of this medusa appe-rs
very strange. The aboral or exumbrella surface, instead of
being convex, as one would expect, is concave when at rest, ex-
cept for a slight convexity over the stomach, and except in
the region of the thinner marginal part of the umbrella, where

- 7 -

it is also convex. The surface of the sub umbrella, on the o-
ther hand, is convex except in this same thinner marginal area.
This is evidently an adaptation to the animal's habit of rest-
ing on the bottom with its oral side uppermost.

The gelatinous layer of the exumbrella is fii'm and elas-
tic and when the animal comes to rest on a flat surface and
the subumbrellar muscles art relaxed, this jelly tends to as-
sume its normal shape and the slight suction which is thus
produced gives the animal somethirg of a hold on the bottom,
and makes it less liable to be disturbed by the action of waves
and currents. The marginal zone of jelly is much thinner and
is capable of motion independently of the central concave disk,
and it is by its frequent movements that currents of water are
kept up bringing food and oxygen to the animal .
Structure of the Jelly.

Keller's description (1883) of the stn.cture of the jelly
in C. polypoides would apply equally well to our species. Be-
sides connective tissue fibres the jelly contains sevei-al kinds
of elements. First there are scattered through it many star-
shaped cells that remind one of osteoblasts and are probably
analogous to them. Ham.ann (1881) speaks of them as Collo-
b lasts. Then there are great numbers of the so-called green
cells, especially in th'i subumbrella. These may be isolated

or in clusters. Each is a sphere with a well marked cell
wall anci contains one or two nuclei that stain deeply, and a
number of what appear to be chlorophyl bodies. Although these
cells have every appearance of being unicellular algae, Keller
thinks they are not algae but that they are essential elements
of the "mesoderm," for accordirg to his experiments they do
not have cellulose in their cell walls.

There are al^o in certain regions peculiar little vesicles
the nature of which is not clear, and which appear in the fresh
tissue to be highly refractile granules. There is a nucleus
to one side of the vesicle, otherwise it is empty in the pre-
served specimens. Accordirg tc Keller, the cell is clear and
colorless at the centre while its periphery is thickly filled
with minute scales or granules.

Color Markings.

The coloring of this semi-transparent animal consists of
certain white markings together with shadings of subdued tints
of brown, green and blue that are often very beautiful. This
is largely due to the last two of the elements in the jelly
that I have just described. The green cells give a general
greenish brovm color to the entire animal, while the refractile
granules produce the white pattern that is so characteristic
of this genus and the related Polyclonia.

- 9 -

If we turn the aboral side of the animal towards us we
find often a brownish band produced by the green cells encir-
cling the disk at the periphery of the concavity. This shades
off on both sides. Deeper in the jelly beneath this there is
a much wider white circle, and from this there are white bands
extending outward along the marginal ridges of the jelly, one
nearly to the tip of each marginal lobe. The bands to the
rhopalial lobes are interrupted, however, by a roughly circu-
lar, transparent area over each rhopaliurn ; and in young spe-
cimens the other bands are not fused with the circle. On the
inner side of this circle there are, deep in the jelly, a num-
ber of white areas tapering towards the centre. Each one is
in the radius of a rhopaliurn, tind extends to a point about
half way from the periphery of the concavity to the edge of the
stomach. These areas, like the marginal spots, are not always
continuous with the circle. At the centre of the umbrella
the stomach ana subgenital cavities may be seen throigh ohe
jelly as a reddish bro^m circular area with a diameter of a-
bout one-seventh of the total diameter of the disk, while sur-
rounding the stomach there is a deep blue halo with points that
extend outward between the last mentioned bands of white.

If now the animal be allowed to return to its usual posi-
tion, the subumbrellar surface will be found to be pretty even-

- 10 -

ly stippled by the greenish brov/n cells in the jelly. Appa-
rently beneath this stippling there is a blue color forming a
circle around the margin of the stomach and extending outward
in broad bands, one along each interrhopalial radius nearly or
quite to a large, more or less distinct patch of blue, that
lies close to the margin between every two rhopalia. The ra-
dial canals and the fine connecting network of tubes appear as
rather indistinct opaque white lines.

The jelly of the oral arms is transparent and colorless,
except for an opaque white stripe beneath the dorsal surface
of ear^h arm of the same character as the white markings of the
umbrella. There is a similar stripe on the dorsal side of
each of the larger branches. which may, or may not, be continu-
ous with the stripe on the main stem. The bases of the oral
funnels are of a delicate blue color, which often extends on
to the brachial canal. The margin of each funnel is a deep
brown, that shades off over the blue, while the small tentacles,
or digitella, that spring from this margin are pure white.
The larger, tongue-shaped vesicles on the arms and oral disk
have a greenish yellow color with a bluish green, longitudinal
stripe. The smaller vesicles on the ar-ras are coloi-ed in a sim-
ilar way and are inconspicuous, but the cluster of ve-ry small
vesicles that occupies the greater part of the oral disk have

- 11 -

a very different appearance, being lightly tinted by fin^r, red-
dish brown pigment spots.

Variability of Mare^inal Structures.

One of the most striking peculiai^ities of this species is
its great variability. Undoubtedly sixteen is the normal num-
ber of the parameres, but we as often find specimens with seven-
teen or eighteen. The number of rhcpalia does not always
correspond to the number of parameres. There are often seven-
teen or eighteen of these and specimens have been found with as
many as twenty-three, Fig. 22. The introduction of additional
rhopalia seems to be a process analogous to the formation of
double monsters in higher animals. We find all stages from a
bifurcated rhopaliiun to two complete parameres in the place nor-
mally occupied by one. Indeed, we may trace the process further
back to forked tentacles in the scyphistoma larva.

As in all Rhizostomae there are no marginal tentacles.
The margin of the disk is, when regular, divided into sixteen
scollops, the sinuses separating these being the sensory nich-
les. Each of these primary lobes is divided into five second-
ary ones, (fonning the 80 marginal lobes mentioned in the diag-
nosis) and from each of the shallow notches separating these

- 12

there is a groove rannin^^ towards the centre for a centimeter
or more along the aboral surface of the umbrella, in the bottom
of each groove the gelatinous layer is extremely thin. [

Structure of the Mar,^inal Sense Organs .
The rhopalia have each a pigment spot on the aboral side
near the extremity and each one lies in a deep sensory niche.
The dorsal sensory groove common in the Pelagidae, Aurelia,
etc. is entirely lacking, althoigh Keller found in C. polypoi-
des a slightly depressed thickening of the ectoderm that cor-
responds to it. The sensory niche and rhopalium are^with the
exception of the pigment spot, similar in all essential partic-
ulars to what is found in Pelagia. The rhopalium is the on-
ly organ in the sensory niche, Fig. 44. It is a hollow, fin-
ger-like projection attached by its base to a low ridge that
runs along the roof to the central wall of the niche. This
ridge is penetrated longitudinally by the continuation of a ra-
dial carnal fi'om the stomach and into the distal end of this ca-
nal the lumen of the rhopalium opens. In the distal half of
the rhopalium the lumen is nearly obliterated by the increase
in thickness of its entodermal lining. Here the entoderm, in-
stead of being a columnar epithelium as elsewhere, is a mass
of parenchyma-like cells each of which contains a large calca-

- 13 -

reous concretion, a so-called otolith. A thin supporting
membrane separates the entoderm from the ectoderm. At the
distal extremity of the rhopalium the ectoderm is a thin cu-
boidal epithelium, while over the rest of the surface it is a
thick sensory epithelium resting on a thick network of fine
nerve fibres. This, in turn, rests on tlie supporting mem-
brane. I have observed no ganglion cells in this layer of
nerve fibres, which is continued under the epithelium of the
rhopalial ridge to the central wall of the niche where it be-
comes imperceptible. There are no thickened bands of these
fibres running to ciliated pockets such as T found (1890) in
Dactylometra, and these fibres probably spread out finally in-
jto a thin network underlying the general epithelium of the sub-
umbrella.

I The one feature in which this rhopalium differs from what
is found i^- Pelagia is the presence of the pigment spot, already
mentioned as lying on the aboral side of the rhopalium imme-
diately c...;Ove the centre of the mass of concretions. This is
an area sensitive to light and only differs from the rest of
the sensory epithelium in that here the superficial cells are
deeply colored by a yellowish bro'.vn pigment. A more careful
exai-nination would undoubtedly show the histology of this strnic-

ture to be similar to what Schewakoff (1889) has found in Aure-
lia.

14

The Oral Arms and their Branches.
I The eight oral arms (Fig. 26) arise from the central oral
disk at about equal intervals and, when an arm is extended, the
distance from the centre of the oral disk to the tip of the
arm about equals the diameter of the umbrella. But the anns
are very contractile and may be shortened to half this length.
The arms are slender and graceful in shape, the jelly tapering
very gradually to the tips of the finest branches. The bran-
ches are ai'ranged alternately. The largest one, which is the
one first formed, is at a point about two-thirds the length of
the arm from its base. From this point the branches gradually
decrease towards the base of the arm, and rapidly decrease to-
Iwi.rds its apex. The general outline of the ar-m, therefore,
including its branches, is roughly spatulate.

The Oral Funnels and Brachial Appenda^;es.
Just below the surface of the oral side of each arm, there
is a longitudinal tube, the brachial canal , that ramifies to
each branch and finally opens to the exterior by funnel-shaped
oscula (os. Fig. 26) at the tips of the numerous ultimate
branches, and at many places along the course of the tube.
The margins of these oscula, or oral funnels are provided with
short, tentacle-like projections, or digitella. These are i
covered by an epithelium containing nettle cells and each has

- 15 - I

an axis of jell.y in which there are transverse plates of great-
er aensity than tiie rest of the jelly, and these give the struc-
ture the cellular appearance first described by Hamann (1881).
The epithelium lining the funnels and tubes is ciliated.
I There open also into the brachial canals the li^mena of the
oral vesicles, (v. Fig. 26). These structures, as already
stated in the diagnosis, have their points of attachment in
the axils of the branches. All except the smallest are flat-
tened laterally. The smaller ones are oval in outline, the
larger ones linear. At one side near the apex there is a
cluster of short processes that Hamann has homologized with di-
gitella.

The Oral Disk.
Although the eight oral arms seem to be placed at equal
distances and to be alike, they are morphylogically in pairs,
each pair being homologous to one of the four lips of an Aure-
lia, for example. The line tnat separates two members of a
pair is therefore according to Kaeckel's nomenclature a perra-
dius. The brachial canals from each pair of arms on entering
the oral disk converge and unite into a single tube that is
continued to the centre of the disk, where it unites with the
other three. In this way the course of the tubes on the oral
disk forms a pattern that resembles a I'laltese cross. At the

16 -

centre of the cross there is attached the large central vesi-
cle. In a living specimen 11 cm. in diameter this measured
3 cm. in length. There are four other vesicles that most near-
ly approach the central one in size and these arise from the
arms of the cross near the junntion of the brachial canals.
In full >^:rom\ individuals there are eight more vesicles, a lit-^
tie smaller, one on each canal distal to the junction. It
is only near the periphery of the disk that the canals are pro-
vided with oral funnels. For most of their course on the disk,
the canals give rise to the very small vesicles finely speckled
with a reddish brown pigment that have already been mentioned.
These have nettle batteries at their tips and are so numerous
as to completely cover the greater part of tlie disk and to hide'
the course of the canals. This mass of small vesicles is not
acquired, ho>v ever, until late. Specimens as much as 6 cm. in
diameter will be found to be without them. In such specimens
we have the five largest vesicles and a number of oral funnels
are scattered along the canals just as tliey are upon the arms.

The Sub^enital Cavities and the Digestive Tract.
At each of the four points of junction of the brachial can-
als there is a si it-like passage dipping vertically into the
jelly of the disk and opening into the stomach. This is a
lens-shaped cavity. It has a gently arched roof and its floor

- 17 - I

consists chiei'ly of four lozenge- shaped areas where the body
wall is very thin and pleated in radial folds. (s.g. Fig. 26.)
These thin parts of the body wall form the roofs of the subgen-
ital cavities, which open to the exterior, each by an eliptical
orifice in the side of the oral disk near the siibumbrella and
in the angle between two pairs of arms. The ovai'y appears as
a band crossing this membrane tangtntially at its greatest
width. Just central to etich ovary there is a multiple series
of very small gastric filaments. These are ciliated and pro-
vided with nettle and gland cells. I say "oA.'ary" because of
the many individuals that I examined, every one was without ex-
ception a female. It is a curious coincidence that of a num-
ber of specimens of Polyclonia that we found in the harbor near
Port Poyal all, on the other hand, were males. The portion
of the floor of the stomach not made up of these lozenge-shaped
membi-anes is bounded by the firm jelly of the oral disk. This
area has the shape of a Maltese cross, and it is in the arms of
this cross between the subgenital cavities that the passages
from the oral canals open into the stomach. Fig. 26.

Near its periphery the floor of the stomach is marked by
radial grooves. These are continued, each into one of the
radial canals^ that extend outward from the edge of the circular
stomach to the marginal r^ion of the umbrella. There are

18 -

regularly t;hirt:;-two of these, sixteen in the radii of the rho-
palia, and sixteen interrhopalial. V/hen the number of rhopa-
lia is increased the number of radial canals may or may not in-
crease in proportion. There are often thirty-four or thirty-
six of them. The rhopalial radial canals are larger and more
nearly straight than the interrhopalial ones and all are con-
nected by a fine net'vork of anastomosing canals, among which
no distinct circular canal can be recognized. The meshes in
the network of canals are not free from entoderm, for in these
areas the entoderm of adjacent canals is connected hy a plate
of entodermal cells, the entoderraal lamella. This lamella is
also in contact with the subumbrellar ectoderri along a line
encircling the umbrella a short distance from its margin, so
tliat there is a complete sheet of entoderm separating the ex-
umbrellar from the subumbrellar jelly.

19

0 N T 0 G E N Y.

Historical Review.
Goette in his well knorvn work on the embryology of Aurelia
and Gotyloi'riiza (1887) attacked the previous work of Glaus
(1883). In 1890 Glaus replied by an article embodying the re-
sults of more recent research on Gotylcrhiza. In this some
of Goette's conclusions are confinneu., notably the one as to
the origin of the septal muscles, and the ectodennal nature of
the lining of the proboscis, but in general the author main-
tains his previous views. This paper has been followed quite
recently by a pamphlet from Goetta (1891) in which, instead of
presenting any new facts, he makes an elaborate attempt to prove
from Glaus' o^vn words that in almost all points Glaus has re-
ceded (1890)from his former position (1883) and now, while re-
ally agreeing with him, seeks to mask this by arabiguity of lan-
guage and by casting reflection upon him. The chief differ-
ence between these two authors is that Goette regards the scyph-
istoma as essentially ar actinian, while Glaus compares it to
a hydroid. Besides this Gootte uelieves the entoderm to a-
rise by multipolar immigration of the blastula cells, the sep-
tal funnels of the scyphistoma to pass into the subgenital cav-

20 -

iLies of the adult, and the rhopalia to be new structures.
While Glaus, on the other hand, maintains that in Aurelia the
entodenn is formed by invagination, the septal funnels have no-
thing to do with the subgenital cavities, and the rhopalia are
then developed in the basal portion of tentacles.

These persistent differences of opinion made it desirable
that a third person should review the whole subject, and for
this reason I was very anxious to obtain developing eggs and to
rear the larvae of Gassiopea. I failed to obtain the eggs
and, therefore, cannot touch upon the question of the origin
of the entodei-m or of the relation of the early scyphistoma
to the actinians. But I did succeed in rearing scyphisto-
mas from plar.ula-like buds and was able to study larvae of
nearly all stages from the bud to the fully formed medusa.
It may be objected that as the larvae that I studied were pro-
bably all produced by budding they can furnish no evidence as
to the course of development of egg embryos. The validity of
this objection depends, it seems to me, upon the manner in
which the bud is formed. In the case of the fission of an
Actinian, naturally, neither of the two nev/ individuals passes
through any lai'val stage, nor would one expect a hydroid stage
in a medusa bud that is produced directly on the body of a
medusa, althoi:^gh one such case has been described. Again, it

21

woula be unfair to expect the hydroid buds on a hydroid to pass
through a planula stage or to have their entodenii produced by
delamination, or immigration ; while, on the other hand, there
is no apparent reason why after these bads are once establish-
ed their future development should not proceed in the sajne way
as in a larvae produced directly from an egg. In Gimoctantha,
according to Brooks (1886), the hydra-like larva produces buds
like itself on an aboral stolon and then all the hydras, the
original sexually produced ones as well as the others, pass |
through a metamorphosis by which they become medusae. No j
difference was observed between the medusae for-med fi'om hydras
that were produced directly from the egg and those from larvae
that were produced indirectly by budding, and beginning with
the hydra stage the steps in the development of the two sets
of medusae are the same. It will be seen from what follows
that the scyphistoma larvae of Cassiopea set free buds of a
yer\^ simple structure, and that when these buus have become
scyphistomas provided with eight tentacles they are essentially
like larvae at a corresponding stage that are developed from
the eggs of other Discomedusae. In the absence of any evi-
dence to the contrary, it seems fair to assume, that we have
here a case similar to OunoclanLha and that the subsequent de-
velopment of this larva is the same as that of sexually produ-

- 22 -

ced larvae of the same species.

This, of course, is a mere assimiption, but it gains in pro-
bability when we find that the development of these larvae cor-
responds in most particulars with what Glaus has found to take
place in the egg larvae of another Rhizostome, Cotylorhiza.
I Up to this time the process of budding in the Discomedusae
has received but little attention. In 1841 Sars described
the budding in scyphistoma larvae that were supposed to be ei-
ther Aurelia or Cyanea. The buds, accordirg to this account,
may groN directly out from the main part of the body of the
larva, or they may be produced on stolons extending outward
from the foot. In either case, several buds may apparently
be formed in various positions on the scyphistoma at one time.
The figures show the buds still attached to the parent and with
a well developed cro^vn of tentacles at the distal end. Agassiz
(1860) also found a similar process of budding to occur occa-
sionally in Aurelia. Goette (1887) has confirmed these ob-
servations and has also found that the larvae of Cotyloi-hiza
tuberculata produce buds. In this species the process, as
described by Goette, is peculiar. A bud is formed as an out-
growth from the body of the scyphistoma, and as this grows it
gradually approaches the shape of its parent, but its relative
position is just the reverse of what Sars found, for the dis-

- 23 -

tal end forms the stem and the proximal end begins to flatten
out into a circumoral disk. In this condition, the bud is
set free and sn'ims about, rotating on its Ion:; axis with the
stem pointing forward. The mouth is formed at the point where
the constriction finally separated the bud from its parent, and
the larva fixes itself by the opposite end.

I In all the above cases this process of budding appears to
be merely an incident in the life history of the individual.
On the other hand, in Gassiopea Xamachana the process of bud-
ding is an important, if not the chief, factor in the perpetu-
ation of the species.

I Development of Cassiopea from Buds.

I. Formation of the Euds.
' Usually on looking over a collection of the scyphistoma
larvae, a considerable proportion will be found to be in the
process of budding. Figs. 1 and 19. There is never any
stolon such as is figured by Sars, but the bud first appears
as a slight swelling on one side of the calyx just above where
it tapers into the stem. jt involves all three layers of the
body wall. Fig. 27. At an early stage in the growth of the
bud, the four septal muscles may be found as four slender cords
of cells embedded in the jelly and apparently growing out from

- 24 -

a thickened area of the ectoderm at the apex ol' the bud. Fig.
28. At this point the suiporting jelly is very thin, so that
the entodei-m ana ectouerm are almost in contact. The bud grad-
ually increases in size, becoming hemispherical and then elon-
gating. As it elongates, a constriction appears close to the
body of the scyphistoma, and now, while the bud continues to
elongate, it alters its shape and the constriction deepens,
cutting off the lumen of the bud from the digestive cavity of
the scyphistoma. The result is an obversely pear-shaped body
attached to the scyphistoma by a very narrow isthmus of sup-
porting substance covered by ectoderm. Fig. 19. Sometimes a
second bud will appear before the first one has dropped off.
In this case the second bud has always the same point of ori-
gin as the first, so that in such specimens the first bud is
attached to the apex of the second one. Fig. 1. I

1 1 . The_ Planula-like Larva.

The bud is finally constricted off while it is still a
simple, pear-shaped, or perhaps more properly, acutely egg-sha-
ped body, without trace of mouth or tentacles and immediately
becomes a pleinula-like, free swimming larva. Like a planula,
its whole surface is covered with cilia, and in swimming it
rotates from right to left upon its long axis, which is paral-
lel to its line of progression.

- ?,5 -

The outline of the larva at this stage is not at all rigid
but a single larva may be seen to assume many shapes if watched
attentively for only a few minutes. It may assume, indeed,
any figure, from a very elongated oval to a short heart-shape.
But, in any case, there is almost always one end that is more
obtuse than the other, and this is always the forward end of
the larva. Figs. 2a, b, and c. |

To one watching a swimming larva it is very noticeable
ths.t one transverse diameter of the body is considerably short-
er than the other. In fact, the larva is usually rather

broadly eliptical in cross section, except when strongly con-

t

tracted, when it may be irregularly quadrangular. Figs. 3
and 4.

In color the larva is white specked with a few greenish
brown spots (the green cells) and it is very opaque. It swims
usually close to the bottom with a varying speed that is some-
times quite rapid. l^ftien it strikes an obstacle it may, v/hile
in contact witii it remain quiet or it may rotate slowly on its
long axis. After a short time it will genei^lly move away a-
gain. In the shallow dishes in which the scyphistomas were
kept, the swimming larvae might often be found hiding;, as it
were, beneath bits of bark and wood to which the scyphistomas
were attached, and when disturbed they would go swimming about.

I - 26 - i

This habit, which afforded a convenient way of collecting them,
I unfortunately did not discover until my last week at the ma-
rine laboratory. These larvae not only have the appearance
of planulae but their habits are the same. Agassiz' descrip-
tion of the habits of the planulae of Aurelia would apply very
well to these non-sexual larvae of Cassiopea. i

The structure of the larva at this stage may be seen in a
longitudinal section, Fig. 29. The ectoderm is uniformly cil-
iated and consists of a rather deep layer of very narrow and
closely packed columnar cells. Their nuclei are small and are
arranged in several rows and the cells themselves are entirely
filled with a very opaque substance. Beneath the ectodenn is
a layer of supporting substance, containing a few green cells
and, occasionally, a colloblast. In a small area, at what was
the distal end of the bud, (D. Fig. 29) this layer is very thin;
there is a thicker zone, which diminishes in thickness towards
the equator, and in the proximal half of the animal the layer
is again quite tliin. In the distal end of the larva the four
septal muscles (s. m. ) are seen, each occupying a tube in the
jelly and beirg directly continuous with the ectoderm. This
is better shown in Fig. 28. The muscle fibres are already dif-
ferentiated and line the wall of the tube, while the nuclei are
more central. It is not usually possible to trace the muscles

- 27 -

for more than half the length of the bud, but I have one speci-
men, one just about to be detached from its parent, in which at
least one of the muscles may be followed for the whole length
of the bud from its distal to its proximal end. There is also
a difference between the two poles of the larva to be noticed
in the entoderm.. Throughout, it is a columnar epithelium,
but at the proximal end it is rather thin and gradually becomes
much t-hicker at the equator. In this proximal half the cells
are somewhat crowded and contain coarse granules. From the
equator to the distal pole the cells gradually become broader
and more clear, and the most distal cells are large and hyaline

III. Formation of the Mouth .

The first change noticeable in the swimming larva is the
formation of the mouth, and this does not occur until two or
three days after the larva has been set free. At the time of
its first appearance, the moutli is a minute opening in the pos-
terior end of the larva. Figs. 3a and b. ^UTiether this
point is identical with the distal, or with the proximal end
of the bud, it is difficult to say. The evidence points in
both directions.

That this point was the distal apex of the bud seems pro-
bable, when we observe, in the first place, that in the comple-

- 28 -

ted bud it is generally the distal end that is the more acute.
This is also tn^e of the poste>"ior end of the S'vimming larva,
in which the mouth always arises. Better evidence is fur-
nished, in the second place, by the position of the septal mus-
cles. It is known that in larvae produced from eggs the sep-
tal muscles arise as ingrowths from the ectodenn of the peris-
tome. In the buds of Oassiopea the septal muscles when fii'st
observed have the appearance of ingrowths from the ectoden^i of i
the distal end of the bud, and it is impossible, at this time,
to trace them to the proximal end. The earliest sta^;e after
the formation of the mouth of v;hich I have sections, has the
septal muscles continuous with the ectoderm of the peristome
in the same v/ay. Compare Figs. 28 and 31.

This seems conclusive, but, on the other hand, the fact ■
must not be overlooked that in the stage last mentioned the
septal muscles are also well developed in the aboral end of the
larva. Moreover, in the bud when about to be set free, while
the entoderm cells in the proximal part are somewhat granular,
those on the distal end are clear and larger than the others,
and thus come to be more like the entoderm in the stem of the
scyphistoma. Fig. 29. This is directly opposed to v/hat is
indicated by the origin of the muscles and makes it possible,
therefore, that the distal end of the bud may, after all, be

- 29 -

aboral as Goette says it is in Cotylcrhiza, and we shoula ex-
pect the two species to a^ree in this particular.

The mouth is at first very small and is slightly funnel-
shaped. It looks under the microscope like a pin hole in one
end of the larva. Fig. 3b. There is no indication at the
surface of any invagination of ectoderm to form an ectodermal
oesophagus. The larva is, however, so very opaque that one
cannot get an optical section of it at this stage. A larva
at this stage swimming in a watch glass will every little while
decrease in speed and Uhti its anterior end downwards until it
strikes the glass. Its forward motion will then cease and it
will for a short time remain attached to the glass, revolving
very slowly on its Ion,?; axis with its oral end tuiTied upwajxi.
One may at such a time look down through the mouth into the
entoder-mal cavity. After a little, the revolutions increase
in frequency, and the larva turns over on to its side, and
swims off. So fcir, then, as I was able to observe, there is
a free passage from the enteric cavity to the exterior at the
time of the first appearance of oral structures and there is
apparently no previous invagination of ectoder-m.

Soon after this, a slight circular concavity appears sur-
rounding the oral region in such a way as to faintly outline
I the proboscis. Fig. 4a and b. Fig. 5 shows a larva a lit-

- 30

tie more advanced. Here the mouth is considerably larger than
in the last stage and has become a narrow slit. A slight
shoulder has developed a little above the equator of the larva,
while the aboral end has become conical. There is apparently .
a thickening in the supporting membrane at the region of the
shoulder, but the opacity of the larva prevents a clear view
of it. This shoulder is the beginning of the peristome and

the part of the animal posterior to it is the proboscis.
There has been no invagination during the foiination of the
mouth, but it is possible that this proboscis arises by an out-
growth of the ectoderm between the mouth and the origin of the
septal muscles. This seems the more probable when we remem-
ber that one of the few points on which Claus and Goette agree,
is in regarding the lining of the proboscis as ectodermal.

IV. The Ei^Jit Tentacle Stage.
The period at which the larvae become attached varies con-
siderably, but some larvae that were reared from buds and had
recently become fixed, were found to be at a stage not greatly
in advance of the last. Figs. 6 and 7. The mouth in these
is circular and well opened. The peristome is distinculy
formed and is eight angled, the four angles in what we may call
the principal radii beir^ somewhat more distinct than the oth-
er four. The stem is also distinctly formed, and in it the

- 31 -

entoderm has apparently begun to thicken.

The stage following this is usually as represented in
Fig. 9. Here we see a large circular mouth. The eight an-
gles of the peristome are produced into eight tentacles nearly
of a size and still very small. The stem has begun to length-
en and to show its characteristic" structure. Larvae at this
stage, are normally quite firmly attached to some foreign body,
but retain their swimming pavers some time longer. ^%en re-
moved from its seat, such a larva will sv/im about as before,
only more slowly, rotating on its long axis, with its stem end
forv/ard. An interesting exception to this mle was found in
a larva Fig. R, that while still actively swimming with stem
undeveloped, had four of its tentacles of about the same size
as in Fig. 9, while tlie four tentacles that alternate with
these were twice as long. This arrangement of the tenta-
cles reminds one of Aurelia, where four tentacle ^ first appear
and these are followed by four others alternating with them.

Fig. 30 is from an obliquely longitudinal section of a
larva in the same stage as Fig. 9. This section cuts the lar-
va in an adradial plane, that is, in a plane that bisects the
angle between two tentacles, the eight tentacles being, four
perradial and four interradial. Fig. 31 is another section
I of the same series. It cuts the larva tangential ly and sho'vs

the connection betv/een one of the septal muscles and the peris-
tome. The larva is covered by a single layer of epitheliim
composed of narrow columnar cells and this is throighout of
nearly an even thickness. The supporting membrane, underlying
this, is rather thin except in the short stem, 'Nhere it is some-
jwhat thicker. The entoderm is about twice as thick as the ec-
'toderm, consists of larger columnar cells, apparently somewhat
vacuolated, and is everyvhare of about the same character. The
stem is apparently entirely filled with the entodenn so as to
be without a lumen. About the mouth the ectoderm is a little
higher than elsewhere and grades impei^ceptibly into the ento-
derm within. Each of the eight short tentacles contains a
plug of entodeiTi cells. The entodermal membrane follows the
general contour of the whole animal except that that portion
of the entiric cavity internal to the periphery of the peris-
tome is divided into four very shallow pouches (g. p.) by
four folds of the entoderm, the interradial septa. At the
peripheral base of a fold the two layers of entoderm are in
contact and are continuous with the entoderm of the interradi-
al tentacle. More centrally, each fold of entoderm sui-rounds
a plate of supporting substance that is continuous with the
supporting membrane of both the oral and the aboral surfaces
of the larva. Compare Figs. 31, 32, 33 and 34. As has been

- 33 -

already pointed out, the swimming: larva is flattenea laterally,
h'ust as is the sexually produced larva of Aurelia, and it is
probele that these entoderraal pouches have arisen at an earli-
er stage, tv/o at a time, in nearly the same way Lhat Goette
I (1887) found them to arise in that species.

We have, then, four tentacles in the plaiies of the septa
and four in the intermediate planes, or perradii.
1 The four septal muscles have an interradial position.
At the peristome they appear as cone-shaped thickenings of the
ectoderm dippir^ into the supporting substance of the septa,
Fig. 31. From the apex of each cone there is a slender cord
of cells that penetrates the supporting membrane of the sep-
tum and continues throigh the jelly of the aboral part of the
larva to the extremity of the stem, or foot, but it does not
appear to have any direct connection with the ectoderm at this
point. This aboral portion of the muscles is perhaps at this
stage a little more differentiated than tlie rest.

Neither in the living animal nor in sections can any trace
be seen of an oesophagus of the nature described by Goette, and
the gastric pouches only reserr.ble those of an Actinian very re-
motely.

34 -

V. The Sixteen Tentacle Stage.

'v'Tiile the eiglit tentacles of the first cycle are still
quite short, eight tentacles of a second cjrcle make their ap- ;
pearance in the intervals between the tentacles of tlie first.
Fig. 10. The animal shown in this figure was, two days before,
a swimming planula-like larva. It is interesting as an exam-
ple of how the irregular increase in the number of tentacles, I
Lhat is so common, is brought about. T'.vo tentacles cf the
first cycle have become bifurcated, so that in each of these j
places there are two tentacles where, if the larva were regu-
lar, there would be but one.

Figs. 32 and 36 are from a series of cross sections of a
larva perhaps a little older than tliis one. Figs. 32, 33 and
34 are consecutive : The first two show the entodei^nal connec-
tion between two gastric pouches at the base of an interradial
tentacle. In Fig. 34 the septum is complete. Fig. 35 is
the second one from this and shows the gastric pouches opening
into the central stomach. A section of the stem is seen in
Fig. 36. The septa do not extend below the expanded part,v\'hat
we may call the calyx 'of the scyphi stoma. There

is a very slight depression in the peristome in the region of
each septal muscle, but no true septal funnels appear. Fig. 32.

- 35

The septal muscles are without a lumen and they each occupy a
tube in the jelly. The --vail of tliis tube is lined by a layer
of longitudinal muscle fibres and within these there is a gran-
ular substance with scattered nuclei : Towards the end of the
stem the muscles gradually become smaller and, the jelly becom-
ing very thin, they are closely applied both to the entoderm
and ectoderm. The ectoderra cells in this region become very
flat- and are covered by a cuticula, and there is now a marked
differentiation between the entoderm of the calyx and that of
the stem.

This is better shown in a longitudinal section of a little
older larva. Fig. 37. The epithelium lining the proboscis is
now very different from that covering its exterior. The lin-
ing epithelium is thick and composed of crowded narrowly colum-
nar cells. At the septa this epithelium passes abruptly, and
in the gastric pouches more gradually, into the entoderm of the
calyx. This is likewise a deep columnar epitheliiun but the
cells are larger, are vacuolated at tlieir bases, and many ap-
pear to be gland cells containing coarse granules at their free
ends. At the plane where the calyx joins the stem there is a
rather sudden transition from this character of epithelium to
the large, clear cells of the stem. The stem is hollow near-
ly to its base. The solid entodermal core of the tentacles

- 36

IS composed of large clear cells with thick walls and apparent-
ly arranged in a single series, the chorda cells common in the
tentacles of coelenterates The base of the stem by which
the scyphistoma is attached to foreign bodies is broadened a
little into a foot. The cuticula extends nearly half the
length of the stem and is in very intimate contact with the
tissue of the plant, or other body, to which the animal is at-
tached. There are short, thread-like processes from the sup-
porting substance of the foot into this part of the cuticula.

Fig. 11 will give an idea of the appearance of a sc;inohis-
toma with the sixteen tentacles well developed. They are now
long and graceful and ornamented by clusters of nettle cells,
that are scattered thickly over the surface, most thickly at
the tip. The mouth is now becoming quadrate, Fig. 12, and
there is a nice co-ordination between the movements of the ten-
tacles and of the mouth. Food is captured by the tentacles.
As soon as the tentacle attaches itself to its prey it is whip-
ped quickly into the mouth, which simultaneously opens toward
the tentacle affected. Once, I saw food taken by two tenta-
cles at the same instant, and the mouth opened in both direc-
tions at one time.

- 37

VI. The Complete Scyphistoma.
With the increase in size of the scyphistoma the calyx is
relatively more expanded and more tentacles are formed. Scyph-
istomas that are still quite small are found with twenty-four
tentacles, and the full number of tentacles, thirty-two, is

acquired long before the scyphistoma had attained its maxi-
n am size. The tentacles appear, when they are arranged sym-
metrically, in cycles of eight ; but the larva is as variable
as is the adult, and the final number of tentacles, while never
less than thirty-two, very often exceeds that number.

The interval between the acquisition of tlie full number
of tentacles and the beginning of tiie next stage seems to be a
long one. The great majority of scyjjhistomas were found in
this stage, and it is during this time that the buds are given
off. The four angles of the mouth are now very pronounced,
and in the proboscis there are four deep longitudinal grooves
corresponding with them. Fig. 46. Between the angles of
the proboscis there are, in preserved specimens, four marked
depressions in the peristome. These are shown in Figs. 46
and 47. The septal muscles do not arise from the bottom of
these depressions but from high up on the outer sides, (Figs.
46 and 47.) It seems hardly possible that these depressions

- 38 -

'are entirely due'to muscular contraction but neither do they
correspona with the septal funnels found in Aurelia.

The four gastric pouches are noiv much deeper than in the
earlier stages and are in conimunication by means of a small
perforation in each septum, close to the base of the interra-
dial tentacle (c. s.. Fig. 47). These perforations, together
with the peripheral part of the gastric pouches, form the "Ring-
sinus" of Clerman authors. There is a slight extension of the
cavity of the "Ringsinus" into the btise of each tentacle. Figs.
38 and 39. Beyond this the tentacle is solid and has the
same stinicture as in earlier stages. The tentacles may in
this, as in earlier stages, be divided into two series accord-
ing to the position in which they are normally held, the one
series being kept more erect, than the other that is nearer the
longitudinal axis of the larva. The two series are equal in
number and their members alternate. Pig5. 11 ana 13, or 14.

The differentiation of the epithelium lining of the prob-
oscis from the general entoderm is even more marked thsjn before.
The two grade into one another on the roofs of the gastric pou-
ches, but on the septa the transition is quite abrupt. Fig. 48.
There is a slight prominence (g. f.) projectir^g from the mar-
|gin of the septum into the stomach. This is covered by a con-
tinuation of the lining of the proboscis and in the angle on

- 39 -

its lower siae the two kinds of epithelium meet. This projec-
tion is noticeable in all my sections of the septa, from this
stage onward. It may be due to contraction of the muscles
but from its position, its Constance, and the kind of epithe-
lium covering it, it seems probable that it is tht rudiment
(Anlage) of a gastric filament, i^'ig. 48 shows the histology of
this region. The epithelium lining the proboscis and the oral
side of the central stomach is composed of moderately deep co-
lumnar cells with a dense, granular contents, small nuclei, and
indistinct cell walls. Among them there is occasionally a
nettle cell. On what I suppose to be a gastric filament, the
epithelium is of nearly the same character. Below this, it
is very different. Flere the cells are more than twice as
deep, are vacuolated,, have larger n.,clei, and the free ends of
most of them are filled with coarse granules that stain with
safranin and are apparently composed of a secreted substance.
VII. The Strobila.

Development of tne Rhopalia.
When the scy]Dhistoma has reached a diameter of about two
millimeters, the first chai'acters appear iJaiat are distinc-
tive of the Strobila. The first noticeable change in this
direction takes place at the bases of the tentacles of the more
erect series.

40 -

This change may be regarded either as the outgrowth of a con-
ical lobe from the margin oi the peristome jearing the
tentacle at its tip or as a conical widening of the basal por-
tion of the tentacle. The former vie"/ is probably the better.
At about this time there appear in the tentacle just beyond the
apex of the cone from 'vhich it springs a fe'v glistening white
bodies. These are the so-called otoliths and mark the begin-
ning of the formation of the rhopalium. Fig. 13. The tenta-
cles containing them will be called the rhopalial tentacles.

These concretions, the so-called otoliths, increase in
number until they form a conspicuous mass, while the basal
cone begins to broaden laterally. This is now distinctly non-
contractile and may be spoken of as a mai'ginal lobe of the pe-
ristome. Figs. 14 and 14a show the par't of the tentacle in
which the concretions lie, to be covei-ed with a thicker epith-
elium and to be a little wider than the distal part, but this
may be due merely to the extended condition of the latter.

In the specimen shown in Fig. 15, we see the first indica-
tion of strobilization . The upper, expanded part of the calyx
is separated from a conical, lower portion by a slight groove.
The marginal lobes have become semi -circular in outline and a
slight elevation is noticeable on the aboral side of each rho-
palial tentacle immediately external to the mass of concretions.

- 41 -

The epithelium at this point is pigmented and forms the first
rudiment of the eye, oc. Fig. loa. Fig. IG illustrates a
more advanced stage where the proximal part of the tentacle is
beginning to take on its final shape and is separated by a pro-
nounced band from the distal pai't, which is still functional
as a tentacle.

We come finally to a stage in which, while the long dis-
tal part of the tentacle retains its characteristic structure
and remains completely functional, the short proximal part has
become completely differentiated into a rhopalium. Fig. 40
is from a longitudinal section of such a tentacle. The rho-
palial part has assumed nearly its final shape. The differ-
entiation of its ectoderm into sensory epithelium, eye spot,
and layer of nerve fibres, is canplete. It has a lumen that
extends outward to the solid chorda-like entoderm of the distal
part of the tentacle and opens towards tht centre into a gas-
tric pocket. The entoaej-mal lining of the lujuen is a colum-
nar epithelium, the more distal cells being deeper and contain-
ing the concretions. Compare Fig. 40 with Fig?.3S ana 39 which,
being interradial, are certainly destined to be rhopalial ten-
tacles.

The growth of the marginal lobes, that when last mention-
ed were semicircular, has continued, and each lobe has now pro-

- 42 -

duced two secondary ones, one on each side of the rhopalial
tentacle. These are connected by a slight ridge, that cross-
es the base of the tentacle on its aboral side, (h. Fig. 40)
These secondary lobes are the rhopalial lobes of the margin of
the umbrella (Fl'iigellappen of German authors) and the connect-
ing ridge is the hood (Deckplatte) that covers the rhopalium.
These marginal structures may be seen in Fig. 17, and this
brings us to another stage in the deve'^opment of the rhopalium,
the absorption of the distal part of the tentacle.

In the strobila shomi in Fig. 17 the rhopalial tentacles
have a very different appearance from what we have seen before.
They are shorter than the other tentacles ar.d are much swollen
at a point just beyond the eye spot. The distal portion is
beginning to degenerate. This process, when once begun, pro-
ceeds rapidly. During the few hours that were spent in making
Lhis drawing, the rhopalial tentacles were reduced in length
nearly one half. The eye spots and concretions were conspic-
uous and in each of the former there was a slight cup-shaped
depression. This is the earliest stage in which I observed
slight medusa- like movements of the ephyra disk. ^igs 41
and 42 are rather oblique sections al right angles to one ano-
ther of rhopalia au about this stage. The tentacle is seen
to be in a process of degeneration for about fifteen-hundredths

- 43 -

of a millirnetei* outward from the ocellus. In this area of
degeneration the entoderm cells are broken down, the support-
ing membrane has disappeared, and the inner boundary of the ec-
toderm is indistinct. The axial m.ass of this part of the ten-
tacle is made up cf loose particles of a finely granular sub-
stance in which, in Fig. 42, we see many small and deeply stain-r
ed nuclei. In Fig. 41 these nuclei are not so prominent and
there are numbers of green cells that apparently escaped into
the central mass when the supporting membrane broke down. There
is evidently a free communication between this mass of disinte-
grating material and the digestive cavity thro-agh the rhopalial
canal . '

I The method by which the shortening of the tentacles is
brought about would seem to be as follows : The axial cells
adjoining the cells that bear the concretion (Fig. 40) first
break down. Why they should do so, and at this particular
time, I cannot say. This disintegration proceeds centrifugal-
ly and it is accompanied by a dissolution of the supporting
membrane. The ectodermal cells then either begin here and
there to break down while still in place and the resulting de-
bris is squeezed into the central cavity ; or else, the cells
migrate, or are squeezed inward and then disintegrate.
The continuity of the remaining ectoderm is maintained, how-

- 44 -

ever. The products of the degeneration probably pass through
the rhopalial canal into the digestive tract. As tliis pro-
cess continues, the invvard movement of the ectoderm cells is
more rapid than their disintegration, so th£.t '.vhen the distal
part of the tentacle is reduced to the size of the rhopalial
part (Figs. 18 and 43) it is a solid mass of small cells with
small nuclei that stain darkly. Some of the.se cells contain
a large vacuole and have the nucleus pushed to one side. Scat-
tered among the small cells, thei*e are numbers cf globular bo-
dies as large as, or larger than, the green cells, and complete-
ly filled with coarse granules that stain deeply with safranin ;
no nucleus is visible in them. "^he ocellus has now become
distinctly cup-shaped. (Fig. 43.)

I At about this time the interrhopalial tentacles begin to
be absorbed in their turn. The umbrella margin has in the
mean time grown out beyond the insertion of each interrhopalial
tentacle and over its aboral side into two lobes with a hood
between. (Figs. 18 and 19.) This sti-ucture, although small-
er corresponds exactly to the rhopalial lobes ana hood, and is
further evidence for homology between the tentacles and the
rhopalia. In the specimen illustrated b.v Fig. 18 the inter-
rhopalial tentacles were in the process of absorption. The
drawing was made betveen the hours of 11 A. M. and 2 P. M.

45 -

At 5 P. M. of that day the tentacles had been reduced to one-
thira the length shown in the figure ana the absorption of the
rhopalial tentacles was very nearly completed.
[ In the later stages of the absoi-pticn of the interrhopali-
al tentacles the broken do^Am material is evidently forced in
some way into the radial canal. This is well shown in Fig.
45, which is from a specimen at about the stage of Fig. 19.
In Fig. 45 we see that the axis of what is left of the tenta-
cle is filled with a confusea mass of disintegrating cells,
small nuclei, and cnedocysts, and some of this mass actually
extends into the cavity of the radial canal.

The rhopaiiim(Fig.44)i3 practically complete at this stage.
The point (x) where the last trace of thb tentacle proper dis-
appearea, is still distinguishable in sections by the presence
of small cells with indistinct cell v/alls, and by the absence
of otoliths. I

Other Phenomena of Strobilization.

'."Tiile these changes are taking place in the margin of the
disk, there are important changes in the general shape of the
animal. The horizontal constriction first noticed in Fig. 15
has deepened, while the fold below it has heightened. At the
same time the upper disk has broadened and flattened until it
assumes the shape sho'-vn in Figs. 18 and 19. The four uepres-

- 46 -

sions in the peristome of the earlier stages hr.ve become nearly
flattened out, all that remains of them being' the hollows be-
tween the projecting angles, or pillars of the proboscis, that
are now very prominent. The specimen from which Fig. 40 was
taken shows a slight cavity (s. f.) in the pei-istome at the
point where each septal muscle joins the general ectodenn.
This is E little more marked in Fig. 49 and it is seen at its
maximum development in Fig. 50 which is taken from a specimen
in which the absorption of the tentacles is nearly complete.
It is a funnel-shaped depression into the septal muscle and is
a vestige of the septal funnel, which, accordii^g to Goette, is
found well aeve loped in Aurelia.

With the increase in width of the peripheral [portion of
Lhe upper disk of ^he strobila, the orifices in the septa be-
come relatively larger, until the septa are reduced to colum-
nar pillars (c. Fig. 50) of supporting substance that connect
the jelly of the peristome or subumbrella with the aboral disk
of jelly, or exumbrella. Tliey are clothed with entoderm, or
perhaps partially with ectoderm, ancl are pierced longitudinally,
each, by a septal muscle. We may speak of these structures
now as columellae.

They are what the Germans call "Septalknoten. " There is
of course no adhesion of the two entodermal plates at these

- 47 -

points, cind they are not homologous with the so-called Septal-
knoten, or areas of adhesion in the Peromedusae. The true co-
lumellae, or "Septalknoten" in the ■^eromedusae are separated,
according to Haeckel's figures, from the areas of adhesion by
spaces in which the gonaslia lie, and are the walls of the large
septal funnels where these pass throi:gh the stomach from the
subumbrella to the exumbrella.

V/hile the septa are shrinking to become the coluraellae,
ridges appear opposite each other on walls of the peripheral
part of the digestive tract between the bases of the tentacles.
The entoderm at the summits of opposite ridges unites and thus
there is formed a series of lines of adhesion extending inward
from the periphery and dividing the space into a series of ra-
dial canals, each ending in a tentacle, whether it be rhopalial
or interrhopalial. The two disks of jelly never fuse along
these lines of adhesion but the entoderm remains between them
as the entodermal lajnella. or cathamjnal plate. At the stage

of Fig. 40 the lines of adhesion occupy half the space from the
margin to the columellae.

At this same stage eight curious nettle batteries appear
arranged s'^rametrically on the proboscis. Perhaps it would be
better to speak of them as special organs for the production
of nettle cells. They are nearly spherical thickenings of the

- 48 -

ectodeiin sunk into the supporting substance from the outer sur-
face of the proboscis. In these structures nettle cells are
to be found in all stages of development.

The lower disk of the strobila remains simply an annular
fold of the body wall until the upper disk is nearly a complete
medusa. The septal muscles in this region bend outward with
the rest of the body wall. Fig. 49. At length, however, the
entoderm grows out as four shallow pouches with gelatinous sep-
ta between containing the muscles, anci very soon after the gel-
atinous septa are perforated so as to allow a fusion of the
entoderm at at their upper armies. Fig. 50. This figure
shows that the body wall has become very thin at the bottom of
the groove that separates the disks, ana the septal muscles in
this region have become constricted. The body wall finally
becomes so thin here that it is ruptured by the movements of
the upper disk which is then set free, and at about tlie same
time the columellae lose their connection with the exumbrella.

Fig. 19 represents an advanced strobila. The lower disk
is drawn as it usually appeared, very much contracted. In oc-
casional moments of relaxation a few small tentacles coula be
seen but they disappeared again before one could count them.
The bua dropped off and began swimming about while I was taking
a short rest from drawing. Pulsating contractions of the um-

49

brella are f irst^noticed at the time when the rhopalial tenta-
cles begin to be absorbed. They are tiien feeble and at long
intervals. At the stage now before us, these movements are
rapid and violent and the rhytlim of movement is interinipted by
few pauses, ai-d these are short. The medusa was set free du-
ring the night after this drawing was made. The following
morning the basal segment had the appearance sho^vn in Fig. 20.
It is a scyphistoma with seventeen tentacles, but the mouth is
merely an orifice lefL after the detachment of the medusa. The
proboscis is not formed yet. I found many scyphistomas that,
from the large size of the stem and sraallness of the calyx, I
concluded had undergone strobilization and I have no doubt that
regeneration and strobilization are repeated a number of times.
At any rate, I am certain that the basal segment becomes a ful-
ly foiTOed sc^q^hi stoma.

- 50

VIII. The Ephyrula.
The medusa that is set free from a strobila of Cassiopea
has a very different appearance from the ephyrula stage in jel-
ly-fish that have eight, the usual number of rhopalia. Coty-
lorhiza has an ephyrula resembling the same stage in the sem-
ostomatous medusae. Good figures of this are given by du Pies-
sis and Glaus and there is a striking difference between these
figures and my Figs. 21 and 22 which are camera drawings of
well preserved ephyrulas of Cassiopea mounted in balsam. Fig.
21 represents a young Cassiopea that has not long enjoyed a
free existence. The general shape of the i;mbrella is like
that of the adult, and there is the same concavity in the cen-
tre of the exumbrella, while the margin curves in the opposite
direction, as in Fig. 52. The typical ephyrula of Aurelia or
Gotylorhiza has eight marginal arms with two lobes at the end
of each and between these, a rhopalium. In Casiopea struc-
tures corresponding to these arms are present to the number of
sixteen, or often more. But these do not destroy the gener-
al circular outline of the animal for they are connected by
thin areas in the jelly with an equal number of ridges alter-
nating with them, which at an earlier stage bore the interrho-

51 -

palial tentacles on their under sides. We have, then, at
this stage the mai'ginal zone of the umbrella marked by a nim-
ber of short radial ridges separated by an equal number of thin
areas. The ridges are in line with the radial canals. At
the principal end of each ridge the margin of the umbrella is
produced into two lobes, those adjoining the rhopalia (sli.l.)
being well marked, the others (i.l.) small and inconspicuous.
In Fig. 22 thei'e are twenty- three rhopalia. This is an
unusually large number and it will be noticed that the number
of marginal lobes has not increased in proportion, so that ir-
regularities of the margin occur in many places. Indeed I
think if a bifurcated rhopalium were added that this one spec-
imen would show all the irregularities of the margin that can
occur in this stage of existence in a Oassiopea. In
scyphistomas forked tentacles may occasionally be fourd, and
bifurcated rhopalia are not uncommon in the medusae. Between
the bifurcated rhopalium and two complete pt.rameres in the place
of one, we find all degrees of duplication: The first stage
beyond the double rhopalium is seen at 1. in Fig. 22, at 3. or
4. there is a greater separation, while at 5. we have two near-
ly complete parameres. Except for this multiplication of mar-
ginal parts the specimen is perfectly normal.

52 -

At this stage the rhopalia have come to lie, as in the
adult, wholly within the margin of the umbrella and project
from its subiimbrella sm^face. The interrhopalial tentacles
have totally disappeared. The lines of adhesion separating
the radial canals are faintly visible as radiating lines of
greater transparency. The four lips of the mouth are spread
out into a cross -shaped figure and one may look directly through
the lumen of the oesophagus into the stomach, and see four gas-
tric filaments. Fig. 21.

Each one of the four lips is nearly square and from its
two outer angles there are two grooves that extend obliquely
inward until they meet and form a V. The point of the V. is
in an ar^le of the oesophagus along which there is a groove
that is continuous with these other two grooves and extends
into the stomach. On the interradial side of each of the
eight labial grooves there may be seen a snail roughly circular
area that is less transparent than the rest. Tliese areas
are the nettle batteries first seen in earlier stages. The
margins of the lips are provided with numerous small processes,
the digitella. These are arranged in a single continuous se-
ries.

The medusa from the strobila Fig. 19, was examined a few

- 53 -

hours at most ai'ter it became fi'ee. The lips were a little
less distinctly quadrate and the digitella were much smaller
than in Fig. 22. On looking through the mouth one could see
the four gastric filaments and an opening to the exterior
throigh the roof of the stomach left by the rupture of the con-
nection with the basal segment of the strobila. Fig. 51 is
a section of an ephyrula at about this stage. In this the
last vestige is to be seen of the connection betA^een the co-
lumella (c.) and the roof of the stomach, and of the degener-
ated remnants of the septal muscles (s.m.) in the jelly near
the aboral opening. The other end of one of these naiscles
is seen at s. m. on the right hand side of the figure. It
extends for some distance into the jelly at the base of a gas-
tric filament and it is penetrated from the exterior by a very
narrow septal flannel (s. f.).

At a little later stage when the opening in the roof of
the stomach has closed both the septal muscles and tiie septal
funnels totally disappear. Sometimes one, sometimes the oth-
er, is the first to vanish.

IX. The Later Stages.

For the present I must pass very briefly over the later
stages in the development of Cassiopea. ^Ihile ^Jle umbrella

54 -

remains unchanged the two outer angles of each of the more or
less quadrate lips are dravm out into extended lobes. Fig. 23.
At the same time the pillars of the proboscis thicken and the
jelly is continued outward along each of these lobes as a mid-
rib. We have then eight oral arms each with a longitudinal
groove, supported by a midrib aiid fringed with digitella ;
arms very similar to those characteristic of the genus Aurcsa,
Haeckel (1879). But it is only the mouth pai'ts of Oassiopea
that may be said to pass through an A^rosa stage, for the oam-
parison cannot, at this time at least, be carried to the other
organs. As the gelatinous axes of the oral arms are thicken-
ed, their bases unite to form the oral disk.

Glaus has described (1883) some of the principal stages
in the metamorphosis of Pilema (Rhizostoma) and Cotylorhiza.
He re^rds the formation of the eight oral arms as a different
process in these forms from what occurs in Aurcsa. There it
is a splitting of the four oral arms, here it is an outgrowth
of the corners of the ephyrula lips. This sounds to me like
the sar:^e thing merely expressed in two different ways. the
comparison that Glaus makes between the process of formation
of the eight arms and the foldings of these arms that results
in the oscula seems hardly applicable in Cassiopea, as will ap-

pear later. Compai^e Figs. 23 and 25.

In the next stage we find, two oral funnels, or oscula,
and a small vesicle developed at the tip of ea-h oral ann.
The other portions of the arm are still open and fringed with
digitella as before, but the outline is no longer a regular
curve, for at intervals there are folds in the margin. The
deepest folas are the most distal and they beccxne progressive-
ly more shallow towards the base of the arm. The central
mouth is itill widely open. The subgenital cavities are
well developed at this stage. Figs. 52, 53, and 54. Figs. 53
and 54 show how they are produced by the great increase in the
thickness of the jelly of the pillars of the proboscis ard of
the oral arms. By the growth of these structures these cav-
ities are necessarily produced. The only special adaptations
are the subsequent growth and folding of the dorsal wall and
the narrowing of the orifice. The marginal lobes of the um-
brella now begin to broaden and thus approach the adult condi-
tion, but there is only a single "velar lobe" between two rho-
palial ones.

At a little later stage when there are three oral funnels
at the tips of the anus (Fig. 25 ) the re-entrant angles be-
tween the pillars of the proboscis have grown inward, met at.

- 56

the centre, and fused, Fig. 24. In this ^vay the lumen of the
oesophagus is divided into four tubes (oe. t. Fig. 24) repre-
senting the grooves that v/ere present in its armies in the ear-
lier stages. In this case the fusion at the centre has gone
so far as to involve the edges of the lips and the labial
grooves of the different pairs of arms are not in open communi-
cation but a short cross -shaped tube connects them at the cen-
tre and the oral disk is no'.v completed. j
j It is interestir^_$ to note that Claus has found a stage
both in Pilema and in Cotylorhiza that, while showing the char-
jacteristic family differences, as also a certain resemblance
Ito this stage in Cassiopea. In all three, the walls of the
proboscis have fused so as to divide its lumen into tubes and
the formation of oscula has begun at the tips of the arms in
such a way that we have on each arm three oscula with a ves-
icle in the angles between them. The occurrence of this
stage in the ontogeny of three so distinctly separated families
imust have some morphological significance and we may regard
these eight primary vesicles as homologous in the three groups.

! The mode of fonnation of tlie oral funnels becomes evident

I

at this stage. They are not formed in Cassiopea simply by a
series of fusions of the lips along the line of the labial
groove, as Hamann found (1882) to be the case in CotyloT'hiza(?) .

- 57 -

It is more like the process irx Pilema as described b}j Glaus.
Each of the primary funnels is represented at first by one of
ithe folds in the margin of the lips referred to above. Fig. 25.
:The fold deepens and its edges are brought together on the
ventral side and fused, leavin^j an opening at the apex of the
Ifold, the osculiim. At tlie same time the labial groove in this
:region is converted into a canal by the fusion of the lips on
'its two siaes. After the fusion all trace of what has occur-
red quickly disappears.

With the division of the oesophagus into four tubes and
the completion of the oral disk our larva comes to be distinct-
ly a rhizostomatous medusa. Further development of the mouth
parts consists in the continued division of the labial or bra-
chial groove into oral funnels and brachial canal, together
with the development of oral veiscles. By the time two or
three vesicles have been formed on the end of each arm a ves-
icle appears in the centre of the oral disk. Except for this
interruption the development of the mouth parts proceeds regu-
larly in a centripetal direction. The funnels and vesicles
are formed first at the tips of tlie anns and then one after a-
nother in regular succession towards the centre. Each of
these primary funnels is the rudiment of one of tlie primary
branches of the arm. When the process of forming funnels has

reachea to about half the length of the am the distal funnels
begin to subdivide. By this subdivision of the primary fun-
nels, funnels are produced of which some are the imdiments of
secondary branches , these subdivide ligain and so on as lon^ as
growth continues. The subdivision is not dicotymous, but
takes place in such a way as to produce alternate branches. A
vesicle is form.ed in some way at about the time of tiie comple-
tion of the fusion of the fold of the lip into a funnel. I

have not been able to deteiTnine, so far, whether the vesicle

I

'is a funnel with the orifice closed as Hamann claims it to be,
or whether it is an evagination from the pedicle of a vesicle
as it seemed to me to be at first, and as Glaus thinks it pos-
sibly is.

Accordir^ to Haeckel (1879) the genus Archirhiza repre-
sents a form th£it was the ancestor of all the rhizostomatous

medusae. Of this genus there are two known species, A. pri-

i

mordiatis, Haeckel, and A. aurosa, Haeckel. They agree in

having four subgenital cavities and eight simple unbranched arms

[that are provided with a single zig-zag rav of closely set o-

'l-al funnels and are devoid of other appendp^es. Hamann sr.ys

Ihat a stage representing this condition is a feature of the

ontogeny of rhizostomatous medusae. From wliat I have said it

is evident that we have no such stage in the development of

- 59 -

Cassiopea Xamachana, for while the labial groove is still open
in the proximal half of an oral arm, in its distal half the
vesicles are formed and branches are in the process of forma-
tion.

The outline of the umbrellae margin has not ohan^-^ed essen-
tially since the last stage. The areas of adhesion have be-
cane much wider than the radial Ccinals they separate and in
them Lhere has appeared a network of anastomosing canals, whil(
the gastric filaments have become numerous. In short we have
nov; followed the larva of our Cassiopea from its first appear-
ance as a bud, to a point where with the exception of the go-
nadia all the organs of the adult are outlined. Here we must
take leave of it.

- 60 -

CONCLUDING REMARKS.

In Cassiopea Xamachana, then, multiplication of individu-
als takes place largely by two kinds of non-sexual reproduction,
strobilization and budding. In regard to the last, several
interesting questions naturally su^^est themselves, such as, —
the origin of budding in the scyphomedusae, which of the known
methods is nearer the primitive one, whether this has any re-
lation to strobilization, and the like; but until much more ev-
idence has been collected th-an we at present possess it will
be impossible to give to them conclusive answers. It seems

to me to be highly probable, however, that the mode of budding

i

jthat occurs in Cassiopea will will be found to be the most high-

i

ily specialized of tliose so far known. It seems to be an es-

ipecial adaptation to overcome the unfavorable effect on the dis-
;tribution of the species caused by the sedentary mode of life
of the adult, a mode of life unusual with meausae. Dwelling
as it does on the bottom ir. quiet lagoons and bays, its eggs
stand lit/tie chance of wide distribution art! the plsjiulse would
not probably swim very far from their mother before becoming
ifixed. The individual buds probably do not swim very far ei-
ther, but the last one of a series of generations of buds may

61

be at a great distance from the parental, sexually produced
scyphistoma.

The resemblance of the swimming bud of Cassiopea to the
planula of Aurelia is extraordinary. Both are ciliated and
have the same movements, the shape is the same, both being a
slightly flattened oval with the more acute end posterior and
it is at ihe posterior end in both that the mouth arises. It
is only when these larvae are examined in sections ti^iat the
difference appears. The bud has, in distinction from the pla-
nula, a thick supporting or gelatinous layer, and the four sep-
tal muscles already formed.

In the development from the bud to the scyphistoma there
is no stage comparable to an anthozoan. This is not an argu-
ment, however, against Goette's theory of the descent of the
scyphomedusa from an anthozoan- like ancestor, for one could
not expect a step in the phylogeny to be recapitulated in a
process of non-sexual development unless this process takes
place during a relabively earlier ontogenetic stage and the
budding in Cassiopea occurs on scyphistomas that have long lost
their anthozoan characters, if they ever possessed any. Goette
regards the early stages in the scyhphistoma as possessing es-
sentially anthozoan characters, in the ectodermal oesophagus
and the four gastric pouches. Glaus admits the existence of

- 62 -

these sti-ucUires but refuses to regard bhem in the same way
that Goette does. Goette says (p. 26) that the scyphi stoma
maintains the typical st-ructure of an anthozoan usually until
the eight tentacle stage. It seems to me tiiaL tiiis stage is
much more ti^ansitory. The septal m.uscles arise in Aurelia
according to (^oette in the four tentacle stage and it is with
the appearance of these very distinctively medusoid sti-uctures
that I should say the larva loses its supposed anthozoan char-
acter. The septal muscles are peculiar to the scyphomedusae, they
are found in no other group of animals and every scyphomedusa
possesses them at some stage of its existence. In the buds of
Cassiopea these are produced very early, while the bud is mere-
ly a hemispherical evagination on t.he side of the scv-phistoma,
and the bud could not, therefore, ever pass through an antho-
zoan stage.

The early development of these muscles is further evidence
for the supposition thai this planula-like bud is a modifica-
tion of a phylogenetically earlier condition with mouth and
Lentacles, perhaps as in Aurelia.

It is to be expected that the organs of a non-sexually
produced animal will be derived from the same germ layers that
give rise to corresponding organs of a related animal that has

63 -

been produced by a sexual process.

Glaus and Goette agree in regarding the lining of the pro-
boscis as of ectodei-mal origin in Aurelia and Cotylorhiza. It
is therefore probable that this is true also of Gassiopea and
that the proboscis is formed as a crater-like fold of the ec-
toderm surrounding the mouth opening. If I were sure of this
I wouIq go a step farther than C-oette and, judgir^ from the
histology, say that not only the interior of the proboscis but
also parts of the septa are clothed with ectoderm. The parts
of the septa referred to appear to give rise to the gastric fil-
aments. This would be further confirmation of Goette 's theory
if it were -not for the fact that these filaments are not devel-
oped in the Anthozoan stage but long ai'terward, at about the
time that the medusa becomes free. I do not believe that
there is any homology between the gastric filaments in the two
groups, Anthozoa and Scyphomedusae.

At first there are eight tentacles, four of them in the
radii of the septa and four interseptal. ViQien the larva is
regular the additional tentacles arise in cycles of eight, there
being next sixteen, then twenty-four and finr.l ly thirty-two ;
out the interpolation of other tentacles is very common.

Agassiz and Glaus have stated tliat the rhopalia in Aurelia
are developed in the basal portions of tentacles. This I find

- 64 -

to be true also for Cassicpea. In this s; ecies I have follov;-
fcd every stage in the development of the rhopalium from the
first trace of such a structure to its completion and I have no
hesitation in saying that tloette's account of this process,
which he persistently upholds^ is entirely erroneous. To show
that the two views are essentially opposed I introduce Goette's
Fig. 49 (Fig. 40a) in which the rhopalium appears as an evag-
ination en the oral side of the margin and quite independent
of the tentacle. The absorption of the tentacles is rapid
and the rhopalial tentacles are absorbed before the rest, so '
that the process is easily overlooked if there is a scarcity
of material. Goette's mistake is probably due to this cause.
Goette says that generally the tentacles are constricted off
but sometimes they are absorbed. I find the latter to be the
only method in Gassiopea.

The gelatinous part of the septa is perforated at about
the time of the appearance of the first tentacles. Later the
septa become reduced to columellae ard the radial canals are
formed by lines of adhesion just as Goette found this to take
place in Aurelia. |

The relations of the septa and septal funnels are about as
Cl&us found them to be in Cotylorhiza. Although the septal

65

muscles extend to the foot, Lhe septa remain ^hort, occupying
only the upper part of the calyx. The septal funnels are a-
bcrtive and ao not become the subgenital cavities.

The strobilization is monodiscous and the basal segment
is regenerated into a scyphistoma. In this I at-;ree with lioet-
te. The free segment is very different in appearance from an
ordinary ephyrula. Stylorhiza must have a similar one. Ltn-
denfeld (1884) found young specimens of this genus witli twent^r-
four I'liopalia. In older ones the number is reduced to six-
teen and fin.-^Jly to eight. In Cassiopea the number of rhopa-
lia is constant in each individual, and depends on the number
of tentacles in th'; scyphistoma stage. There are, as a rule,
half as many rhopalia as there wore tentacles, every alternate
tentacle havir^ given rise to a rhopalium. The irregularities
in the marginal sti'uctures of the adult^that are so strikingly
frequent, ai'e to be referred back to irregularities in the ar-
rangement of the tentacles of the larvae from which they are
developed.

The young medusa has at first a simple quadrate mouth
with slightly spreading lips. Later these are drawr. out into

eight lobes so that as far as the mouth parts are concerned we

I
have an Aurosa strge.

There is no Archirhiza stage in Cassiopea but there is a
- 66 -

stage with the oesophagus reduced to four tubes and with three
osGula and an oral vesicle on each arm, which it has in cornnon
with Pilerna and Cotylorhiza.

A somewhat cursory examination of my material made to de-
termine the mode of development of the oral funnels and vesi-
cles, inclines me to the views on this point upheld by Glaus,
rather than to those of Hamann.

A s^^/Tiopsis of the principal characters of the adult medu-
sa is given in the diagnosis of the species and the following
section. l^lTiat most strikes a casual observer, is the peculiar
concave exumbrella and the animal's m^ode of life. The only
other species that has been described as naving a similar shape
is Gassiopea pol^^^oides. Keller, but I have observed that Poly-
c Ionia frondosa also approaches this conaition. The habit of
living in schools in shallow water and resting; on the bottom
with the mouth upwards has been noticed by a mmber of persons
in other species of Gassiopea and in Polyclonia and seems to be
common in these two genera.

- 67 -

LIST OF PAPERS REFERRED TO.
1829. Tilesius. Zur Naturgesohichte cler Medusen, Kova Acta

Phys. Med. Y,. G. Vol. 15. p. 266.
1841. Sars. Uber die Ent-wicklung der Medusa aurita und

Cyanea capillate, Arch. f. Naturg. Vol. 7.
1849. Milne-Edwards. Les Zoophytes, Cuvier's Regne Animal

illustre. PI. 51.
1853. Frantzius. Uber die Jungen der Cephea (Gotylorhiza) ,

Zeit. f. wiss, Zool. Vol. 4. p. 118.
1860 L. A^assiz. Contributions to the Natural History

of the United States of Merica. Boston. Vols. 3 and 4.
1869. Kaeckel. Crarnbessiden, Zeit. f. \»;iss. Zool. Vol. 19.

p. 509.

1877. Clsius. Die Polypen und Quallen der Adria. Wien.

1878. 0. and R. Hertwig. Das Kervensystem und die Sinnes-
organe der Medusen. Leipzig.

1879. 0. .^id R. Hertwi^. Die Actinian. Jena.
Kaeckel. Das System der J-ledusen. Jena.

1881. A. A^assiz. Polyclonia frondosa. Nature Vol. 24.
p. 509.

Archer. Medusae. Nature Vol. 24. p. 307.

Glaus. Uber enige bislang noch unbekannte Larvens-

68

tadien von Rhizostoma. Zool. Auz . 1881. Ko. 76. p. 79.

Haeckel. Report on the Deep-Sea Medusae. Challen-
ger Reports. Zoology. Vol. 4.

Hamarm. Die Mimdarme der Rhizostomen und ihre Au-
hangsorgane. Jena. Zeit. Vol. 15. p. 243.

du Plessls. Reraarques sur les Metamorphoses de la Gas-
siopei^ bourbonnienne. Bull. Soc. Vaudois. Lausanne,
2nd series. Vol. 17.

1882. Guppy. Habits of Scyphomedusae Mature. Vol. 27.
p. 31.

Rewkes. Notes on the Acalephs of the Tortugas.
Bull. Mus. Com. Zool. Cambridge. Vol. 9. Mo. 7.

Lendenfeld. Uber eine Uber gangsform zv.'ischen
Semostomen und Rhizostomen (Pseudorhiza) . Zool. Aug. 5
Jhy. p. 380.

1883. Glaus. Untersuchungen uber die Organisation und
Entwicklung aer Medusen. Frag und Leipzig.

Keller. Untersuchungen uber neue Medusen aus dem
rothen Meere. Zeit. f. v/iss. Zool. Vol. 38. p. 621.

1884. Glaus. Die Ephyren von Cotylorhiza und Rhizostoma,
Arb. zool. Inst. Vi/ien. Vol. 5. p. 189.

Lendenfeld. Zur Metamorphose der Rhizostomen. Zool.

69 -

Auz. 7 Jhig. , p. 4^:9.

1885. Haacke. Pseudorhiza. Biol. Central. Vol. 4. p.
.^■91. '

1886. Metschnlkoff . Embryologische Stuaien au Medusen.
Wien.

Brooks. The Life History of Hydromedusae, a discus-
sion of the origin of Medusae and of the significance of
Metagenesis. Mem. Bost. Soc. Nat. Hist. Vol. 3. No. 12,
also Mem. Biol. Lab. Johns Hopkins Univ. Vol. 1.

1887. Goette. Entv/ickluiigsgeschichte des Aurilia aurita
j and Cotylorhiza tuberculata. Hamburg und Leipzig.

1888. Fisher. Scyphostomata of Acraspedote medusae. Abs.
in Jour. Roy. Mic. Soc. 1888. p. 965.

Lendenfeld. Die Austral ischen rhizostomen Medusen.
Zeit. f. wiss. Zool. Vol. 47. p. 201.

1889. Vanhoffen. Semaeostome und rhizostome Medusen. Leuok-
art und Chun's Biblioth. Zool. 3 Heft.

Schewiakoff . Zur Kenntness der AcalepUBnaiiges.
Morph. Jahrb. Vol. 15. p. 25.

1890. Bi^elow. The marginal sense organs in the Pelagidae.
Johns Hopkins Univ. Circ. Vol. 9. p. 65.

Glaus, ifber die Blntwicklung des Scjrphostoma von Coty-

70 -

lorliiza, Aurelia unci Chrysaora. Arb. Zool. Inst. IVien,

Vol. 9. p. 29.
1S91. Cxoette. Olaus unci die Entwicklung der Scyphomedu-

sen. Leipzig.
189:-^. Bi^elow. On Reproduction by Budding in the Disoo-

medusae. John Hopkins Univ. Giro. Vol. 11. p. 71.
Bi,a:elo'v. On the Development of the Marginal Sense

Organs of a Rhizostomatous Medusa. Johns Hopkins Univ.

Circ. Vol. 11. p. 84.

71

EXPLANATION OF THE FIGURES.

All the figures from 1 to 20 and Fig. 26 are free hand
drawings made from the living specimens. Figs. 21 to 25 are
from well preserved specimens mounted in balsam and were out-
lined with the camera lucida. The remaining figures are cam-
era lucida drawings of microtome sections.

Lettering common to all the Figures .

b.

bud

c.

columella

c. d.

circumoral disk or peristome

c. s.

circular sinus

ex.

calyx

d.

digitellum

ect.

ectoderm

e. 1.

entodermal lamella

ent.

entoderm

6. u.

exumbrella

S-

stomach

g. f.

gastric filament

g- P-

gastric pouch

h.

hood

- 72

i. 1. interrhopalial lobe

i. t. interrhopalial tentacle

j. jelly or supporting membrane

m. mouth

n. f. nerve fibres

0. a. oral arai

00. ocelus

0. d. oral disk

oe. oesophagus

oe. t. oesophagial tube

OS. Osculum

ot. rhopalial concretion (otolith)

p. proboscis

p. p. pillaj- of the proboscis

r. c. radial canal

rh. rhopalium

rh. c. rhopalial canal

rh. t. rhopalial tentacle

s. stem

s. e. sensory epithelium

sep. septum

s. f. septal i;unnel

73

s. g. subgenital cavity

s. m. septal muscle

s. u. subiimbrella

t. tentacle

V. vesicle

Fig. 1. A scyphistoma in the process of budding. In
this case a second bud (b,,) has formed before the first (b,)
is set free.

Figs. 2a, b, and c. A planula-like larva showing the
changes of shape assumed by one specimen dulling a few minutes.
The arrov/ shows direction of motion.

Fig. 3a. A larva in which the moutii has just formed.

Fig. 3b. Oral aspect of the same specimen.

Figs. 4a and b. A slightly older specimen viewed in two
planes at right angles to one another.

Fig. 5 Larva with first traces of the proboscis and cir-
cumoral disk.

Fig. 6. Scyphistoma very recently attached.

Fig. 7. Oral aspect of a similar larva.

Fig. 8. A scyphistoma with rudiments of eight tentacles
but still swimming freely.

74

Fig. 9. An atte.chea scyphistoma with rjoLiments of eight
tentacles. More usual form.

Fig. 10. Scyphistoma with rudiments of the second set of
eight tentacles.

Fig. 11. Scyphistoma with sixteen tentacles fully devel-
oped.

Fig. 12. Oral aspect of a similar specimen.

Fig. 13. Scj-phistoma showing first traces of rhopalial
structures.

Fig. 14. Scyphistoma at a slightly older stage.

Fig. 14a. Small part of the margin of a similar larva.

Fig. 15. An early stage in strobilization.

Fig. 15a. A rhopalial tentacle of the same specimen seen
from the side.

Fig. 16. An older rhopalial tentacle.

Fig. 17. Strobila in which the rhopalial tentacles have
begun to degenerate.

Fig. 18. One in which the interrhopalial tentacles have
also begun to degenerate.

Fig. 19. A complete Strobila.

Fig. 20. The basal segment remaining after strobilization

Fig. 21. An Ephyrula recently set free.

Fig. 22. A specimen of about the same age showing varia-

- 75 -

' tions of the margin.

Fig. 23. Moutli parts of a young medusa in the Aurosa
stage.

Fig. 24. Oral disk of an older specimen.

Fig. 25, One of the oral arms from the same specimen.

Fig. 26. Floor of the stomach and the ornl arms of an a-
dult viewed from the ah oral side. The roof of one subgenital
cavity is removed and a thread is represented as passing thro'
the external orifice into this cavity.

Fig. 27. Section of a young bud. x 313.

Fig. 28. Section through the distal apex of an older bud
showir^g the origin of a septal muscle. Zeiss H oc.2.

Fig. 29. Longitudinal section of a planula-like larva.
Zeiss DD oc.2. D was the distal,? the proximal end before
it was set free.

Fig. 30. Adradial section of a scyphistoma of tht same
age as Fig. 9. Zeiss DD oc.2.

Fig. 31. A tangential section of the same larva showing
the connection of a septal muscle with the circumoral disk.
Zeiss H. oc.2.

Figs. 32 to 34 are consecutive transverse sections of one
individual. Fig. 32 shows the continuity between the ento-

76 -

derm of adjacent gastric pouches at the base of an interraciial
tentacle. Fig. 34 is laver and here the gelatinous septum
completely separates the two pouches. Zeiss. H oc.2.

Figs. 35 and 36 are from the same series. Fig. 35 is
the second section below Fig. 34. It just clears the oesoph-
agus.

Fig. 36 is through the upper part of the stem. Zeiss.
DD oc.2.

Fig. 37. Longitudinal section of a scyphistoma with six-
teen tentacles, probably a little younger than Fig. 11. 490.

Figs. 38 to 44 illustrate the development of the rhopalia.

Fig. 38. A radial section throi^h the base of an inter-
radial tentacle in a fully developed scyphistoma. xH oc.2.

Fig. 39. A tangential section thraugh the base of another
interradial tentacle of the same larva. xH oc.2.

Fig. 40. A radial section from the base of a rhopalial
tentacle somewhat older than Fig. 16. Zeiss K oc.2.

Fig. 40a. A copy of Goette's Fig. 49, introducea for com-
parison.

Fig. 41. A radial section thi'ough a rhopalial tentacle
in the stage of Fig. 17. Zeiss H oc.2.

Fig. 42. A tangential section of a similar tentacle of
the same age in the plane x y of Fig. 41^ Zeiss H oc.2.

- 77 -

Fig. 43. Radial section of a rhopaliiim in the stage of
Fig. 18. Zeiss H oc.2.

Fig. -'i4. Radial section of a rhopalium in about the stage
of Fig. 19. Zeiss H oc.2.

Fig. 45. A similar section throtigh the degenerated rem-
nant of an interradial tentacle from the same specimen.

Fig. 46. A somev/hat obliquely transverse section of a
fully developed scyphistoma showing the relations of the sep-
tal muscles to the depressions in the circumoral disk. Zeiss.
DD. 0C.4.

Fig. 47. Section in the plane of an interradius from a
similar larva. Zeiss. C oc.2.

Fig. 48. Part of the opposite side of a similar section
of the same series, more highly magnified to show the histolo-
gy of the parts. Zeiss. H oc.2.

Fig. 49. Radial section showing the course of a septal
muscle in a strobila. X 313.

Fig. 50. A similar section from an older specimen. X
Zeiss DD oc.2. X point of separation between the t#o disks.

Fig. 51. A r.edian verticle section of a young medusa that
has very recently become free X is opposite the opening that
formerly lead into the lower disk of the strobila. Zeiss DD
oc.2.

- 78 -

Figs. 52 to 54. Parallel sections from a sirgle medusa
intermediate in age bet."een Figs. 23 and 24. The mouth opens
freely to the exterior, while the fonnation of vesicles and os-
cula has begun at the tips of the oral arms.

Fig. 52 is nearly radial ; the other two are tangential.

79

II T A.

The author of this thesis, Robert Pa;/ne Bigelow, is the
son of Otis and Margaret Payne Bigelow, and was born in Bald-
winsville. Mew York, July 10th, 1863. Since 1868 he has resi-
ded in the city of Washington, where he attended the public
schools ar.d ai'tenvards stuaied for two years, until 1882, in
the Preparatory School of Columbian University. A year was
then spent as book-keeper for the firm of Otis Bigelow & Co.,
after which he entered the Scientific School at Harvard Uni-
versity, whence he was graduated in 1887, with trie degree of
Bachelor of Science, ma,gyia cum laude.

Another year was spent in business, and then he entered
the Johns Hopkins University, taking Animal Morphology as his
principal study, with Physiology and Botany as subordinate sub-
jects. I'.'hile in this University he has held the positions of
University Scholar, Fellow, and Enice Fellow.

80 -

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