30. 
31. 
34. 
35. 
36. 
. Embryo with sixty-four lenticular cells, forming the epiblastic vesicle, and thirty-two masses, composed of 
- Cell at the beginning of the sixth plane of segmentation. epl. Epiplasm. hi pl. Hypoplasm. 
. The epiblastic layer now grows faster than the hypoblast, and the space between them i increases, while a at 
. Embryo forty hours after impregnation. ed!. Edge of the epiblastic disk. hd. grok which fuses ie 
. The oral pole of the embryo three days and ten hours after fecundation. ¢ 5. Epiblast. or. Thickened e “i _ 
aT, 
ine 
ng 
EMBRYOLOGICAL MONOGRAPHS. | 
transparent protoplasm, the hypoblast (5). 
points they grow together. Appearance of the ovum towards the close of the formation of the seventh — 
plane of segmentation. epl. Epiplasm. pl. Hypoplasm. . Bridge connecting the t 
Appearance of an ovum a day after fructification. epl. Epiplasm. eb. Epiblast. hb. H ast. h pl. Hy- 
poplasm. 2. Cell nucleus. vt. Vitellus. : ae 
The wide cavity between the two layers, epiblast and hypoblast, now becomes filled with a gelatinous layer. — 
The embryo becomes ciliated, and at the point where epiblast and hypoblast fuses, the epiblast (¢ 0.) i 
thickened and forms a disk, through which opens a mouth. Embryo thirty hours after impregnation. — 
eb. Epiblast. ¢d!. Disk-like epiblastie thickening. The disk is seen between the dots (e0!). hb. Hypo- \ 
blast. wbr. Umbrella, gelatinous tissue of a middle layer. 
the epiblast at this point. wbr. Umbrella. The epiblast (¢b.) is spread as a thin invisible layer over the 7 
surface of the umbrella. . 
blast, which later breaks through and forms a mouth. hb. Hy poblast. 
Oral pole of an embryo six days and twelve hours old (after fecundation), with mouth widely open, and oe 
border of the umbrella (wir.) drawn somewhat together. ¢b. Epiblast. 4b. Hypoblast. @. Solid axis 
of tentacle. ¢ Conical projection at the extremity of the tentacle. Te 
Older larva with lips and umbrella shown from below. The tentacles are widely extended. cb. Epiblast. 
ga. Stomach. Jab. Lips of entrance to stomach cavity. 2tcy. Nematocyst. vel. Velum. ¢. Connec- as 
tion of the bases of the tentacle with the bell margin. 7 
Oldest larva, which swims for the most part by means of movements of the velum (vel). No cilia. ga. Stom- 
ach. lab. Lip. ntcy. Nematocyst. ta. Tentacle. The small buds on the rim of the bell indicate the future. 
sense bodies as well as rudimentary tentacles. wr. Umbrella. ¢. Tentacular axis of solid ea 
cells, and the same axis continued from the base of the teutacle to the bell margin. 
