MUSEUM OF COMPARATIVE ZOOLOGY. Zio 
vt. c. Vitelline cells forming a ‘‘ protoplasmic network” through the yolk contents. 
In many of the figures only a few of these cells are drawn. They are 
found throughout the whole contents of the egg. 
Y. Unknown body, possibly remnant of membrane which encloses the egg. 
All the figures, with the exception of Pl. IV. figs. 3-7, were drawn by the author 
with an Oberhiuser camera, objective B. B., eye-piece 2, Zeiss. Size reduced one half 
in photography. All figures except Pl. II. fig. 2 were drawn from living eggs and 
larve. The last mentioned was treated with dilute acetic acid before drawing. 
<o-12. 
ee 20: 
ASO 
$5224 
38 
PLATE I. 
Immature female gonophore with egg in the interior. Nucleus and nucle- 
olus shown through its walls. Attached to parent. 
Egg in a small immature gonophore, with sinuses between ovum and bell 
walls of gonophore. 
Female gonophore found free in water. Enclosed ovum .5 mm. in diameter. 
The ovum in the act of escape from the gonophore. 
Ovum removed from a gonophore (artificially). 
Ovum just escaped from gonophore (naturally), .45mm. in diameter. 
Egg showing the formation of a primitive furrow at one pole. 
The same, ten minutes older than last. 
The same, fifteen minutes older. 
The same, twenty minutes older. 
The same, twenty-five minutes older. 
The same in two-cell stage, thirty minutes older than Fig. 7. Diameter 
35mm. The egg traced from Figs. 7-12 is .1mm. smaller than that 
from Fig. 13 on. 
Two-cell stage with beginning of a secondary furrow (se.), .60 mm. in long 
diameter, .43 mm. in least diameter. 
Two-cell stage, ten minutes older than Fig. 13. .60mm. in diameter. 
The same, fifteen minutes older. 
The same, eighteen minutes older. 
The same, twenty minutes older. 
The same, twenty-five minutes older, showing the formation of the sec- 
ondary furrow, extending in a horizontal direction over the surface of 
the ovum. It also shows the deviation of the primary cleavage plane 
(1 c/. pl.) from a straight line when seen in profile. 
Formation of a 4-cell stage by the closing in of the secondary furrow (se. ). 
The furrow is still open at each end. Thirty minutes older than Fig. 
13, .50 mm. in diameter. 
Four-cell stage, thirty-five minutes after Fig. 13. 
The same, forty-five minutes after. 
The same, fifty-five minutes after. 
The same, one hour and ten minutes after. 
VOL. xI.— no. 11. 18 
