EMBRYOLOGICAL MONOGRAPHS. 
IPMN IB} Ile 
Development of the Hyprowa. Figures from Nicouaus KieiNenBere and GrorcE J. ALLMAN. 
1-11. Development of Hydra, from Kleinenberg, Hydra. Eine Anatomish 
“IO OF Hm OO 
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10. 
C. cav. Cavity of the planula. T. ta. Permanent tentacular processes. 
cp.  ‘‘Structureless capsule.” ta’. Provisional tentacular appendages. 
E. cb. Epiblast. &  Sueker-disk at ‘ proximal” extremity. 
eb!. Epiblastic prominence. Situation of mouth at “distal” extremity. 
n 
ex.s. External pellicle, or perisare. 6. Cellular bodies surrounding the ovum. 
r 
G. gu. Gastric cavity. Orifice formed by an invagination of a ten- 
H. hb. Hypoblast. tacular process (¢@/). 
hb!, Hypoblastic elevation under the epiblastic. p. Chamber filled with ‘* granular proto- 
J8 Mes Internal pellicle, or perisare. plasm.” 
M. mb. Membrane. o. Diverticulum from the cavity of the blas- 
N.nl. Nucleus (2). tostyle from which the hernia-like bud 
O. om. Ovum. forms. 
or. Thin region of walls at one pole where a w. Highly refractile body. 
mouth is later formed. 
Entwicklungsgeschichtliche 
Untersuchung. PI. II., Figs. 10, 11, 16, 17, 18, 19 ; Pl. IIl., Figs. 11, 12, 13, 14, 15. 
Ovum of H. aurantiaca in ameboid condition, with chlorophyll granules and yolk spherules (pseudocells). 
The large cell in the center of the figure is the germinative vesicle.“ Der Keimfleck des Keimblaschen ist 
in der Fig. nicht zu sehen, war aber noch vorhanden,” Kleinenberg. The processes thrown out in all 
directions are protoplasmic. The yolk cells are formed from the protoplasm. 
_ Germinative vesicle liberated from the enveloping substance. mb. Membrane. 2/7. Germinative dot. 
w. Refractile body in the germinative dot. 
. Ovum shortly before the rupture of the surrounding cells (#). om. Ovum. 
. Segmented ovum with two spheres. 
. Still older ovum, with four spheres. No segmentation cavity is formed. 
Morula. 
Section through the germinative vesicle of ZH. viridis. ex. s. External pellicle. ga. Body cavity. 7. s. In- 
ternal pellicle. 
There is a layer of cells surrounding the body cavity inside the internal pellicle. The external pellicle 
(perisare of marine hydroid ?) is ultimately lost ; the internal is absorbed. 
Embryo of H. aurantiaca. eb. Epiblast. hb. Hypoblast. 7. s. Internal pellicie. The external pellicle is 
ruptured and thrown off. The caudate cells (‘‘nerve-museular”) form in the outer layer (¢)). The inner 
layer (1b) in this stage becomes cellular. 
Embryo of last-named species, seen in plane of longer axis. The future mouth opens near o7!. ¢b. Epiblast. 
hb. Hypoblast. 7. s. Internal pellicle. 
The same with the walls of the two poles similar. ¢b. Epiblast. 1b. Hypoblast. 7. s. Internal pellicle. 
