*& 
NoOr2Z|\) CHE EGG OF AMTIA AND TTS “GLEAVAGE. B27) 
and is soon absorbed. About this time the larvae are ready to 
leave the nest with the male fish. Frequently we have seen 
the entire brood, generally numbering several hundred, huddled 
so closely together that they formed a black mass moving along 
in close company with the parent. If disturbed, the parent 
rushes off, setting the water in commotion by its movements, 
and the brood scatter to conceal themselves at the bottom. In 
a short time, if one remains perfectly quiet, he may see the 
larvae come forth in small groups from their hiding-places, and 
perhaps the return of the parent. 
The following table shows the rate of development. The 
cleavage times are based upon observations made on a single 
egg, while the times recorded beyond late cleavage are based 
upon data obtained by following the development of a second 
ere 
DD: 
AGE IN Hours. LENGTH IN MM. STAGE OF DEVELOPMENT. 
_— -- Oviposition, beginning of 
2.24 — First cleavage, “ ‘ 
3.28 — Second “ a 
4.20 — Third et cs as 
5:22 — Fourth “ e sc 
6.20 _- Fifth He % a 
7-25 = Sixth it a 
10. — Late .$ 
TGs — Blastula 
40. —_ Gastrula, early 
70. a Embryo visible 
160. — Embryo begins to move 
200. 5-6 Embryo hatches 
250. 6-8 Appearance of pigment 
360. 9-10 Yolk-sac absorbed 
480. 12-14 Pelvic fins appear 
720. 17-20 —- 
CLEAVAGE. 
Our observations on the cleavage comprise : first, a study of 
surface phenomena, followed continuously on the living egg ; 
secondly, a comparison of corresponding stages as traced on 
prepared material ; and thirdly, a study of serial sections. 
In following the cleavage of the living egg we found it con- 
venient to proceed as follows : The eggs still attached to blades 
