192 ADAM SEDGWICK. 
parts than in others; the main strands were obviously con- 
tinuous with the surrounding membrane, which in its turn 
was obviously continuous with the very loose reticulum out- 
side. 
I have no observations on the transformation of the simple 
male pronucleus of the early stages into this complicated 
structure, nor have I any on the transformation, quite as 
remarkable, of the few chromatin masses which represented 
the female pronucleus in the last described ovum into the 
complicated structure present in this case. 
3. The Nucleus of the Ectoderm in the gastrula 
and later stages.—lI have already (p. 190) said all that I at 
present have to say about this nucleus. It is much smaller 
than the earlier nuclei, and not specially favorable for study. 
I have little doubt, however, that the network of which it is 
composed is continuous with the exterval spongework. 
4. The Endodermal Nuclei.—As I have already said 
there are apparently no nuclei in the endoderm masses of the 
segmenting ovum, or, in other words, no part of the first seg- 
mentation nucleus enters, so far as I could see, these masses 
during the segmentation. At any rate there can be, I think, 
but little doubt on one point, viz. that the endoderm masses 
do not during the segmentation contain any structure like a . 
nucleus as ordinarily described. They do contain, as I have 
already said, a densely reticulated central area, but this is with- 
out any deeply-staining chromatin so characteristic of a nucleus. 
Can this area represent a nucleus, perform the functions of a 
nucleus for these endodermal masses ? 
Without venturing to decide the question I may draw atten- 
tion to two facts brought out by the study of the large nuclei 
described under heading 1 (p. 185). These are: (1) The 
nuclear spongework is perfectly continuous with the extra- 
nuclear spongework, and (2) the amount of concentrated deeply- 
staining matter may be very small, as in the undoubted nucleus 
of fig. 2 in which the three masses in the figure represented 
the whole of the especially deeply-staining matter present. 
The question, therefore, presents itself; what is the essential 
