Fig. 3. 
(90) 
PLATH XXXIX. 
Ctenolabrus, under (inner) surface. Treated as Figs. 1 and 2, [Plate XX XVIII], four 
hours after 32-cell stage. One hour after Figs. 1 and 2 [Plate XX XVIII]. In this cap the 
nuclei of the endoderm are strongly colored and very well defined. One can see by the nuclei 
that the endoderm extends for only a short distance under the cap. The majority of the 
nuclei are outside the cap. 
{Seven sections]. Three hours after 32-cell stage. [be = blastocoele; pb = periblast]. 
(Os, Mk. 3ds). 
Second section shows only one or two outlined cells, the outlines being indistinctly marked. 
The third section shows two well-outlined cells; the right is sharply marked inferiorly. 
There is a partial outline of a dark cell of the cap. 
The fourth section shows the first appearance of the sub-germinal plate. All the red cells 
are shaded by dotting. 
The sixth section shows the subgerminal plate thinner. 
The sixteenth section shows on the left a red cell that looks as if it was to enter into cap. 
The twenty-sixth section is near middle. Here sometimes no nucleus is seen in periblast, 
at other times one or even two. Subgerminal plate very thin, wavy in outlines as in section 
sixteen. 
The twenty-eighth section shows an inner cell in process of splitting off, possibly destined to 
become one of the cap cells. 
The thirty-third section showed a similar case. 
I think it is possible that cells are still added to the cap, but that this process is nearly con- 
cluded, so that the periblast as a cell layer may be now considered established. 
{Later stage. bce = blastocoele; ep = epidermis; pb = periblast]. Section near middle. 
The periblast is very thin, vanishing or nearly so near the center of field. Epidermis well 
marked off. 
On left is a single periblast cell that looks as if it was a cap-cell. The fact that the periblast 
becomes so very thin indicates that cells are added to the cap up to about the time the ring 
begins to form. 
The nuclei of the periblast are still confined to the thickening beneath the margin of cap; 
on the left [i. e. lower end of figure] a single nucleus is somewhat advanced from the margin 
towards the center, but this is exceptional in these sections. 
— 
