ENTRY OF ZOOXANTHELL2® INTO OVUM OF MILLEPORA. 703 
vealed no chromatin, yet as a rule minute feebly staining 
strands could be found projecting here and there from the 
nuclear membrane. Practically always a more or less dis- 
tinct achromatic reticulum was to be made out in these 
clear nuclei. 
The next phase exhibited by the nucleus was associated 
with the termination of growth on the part of the ovum. 
The chromatin, absent from the last of the preceding stages, 
can again be discerned, and reappears as minute feebly 
staining granules, which are often clearly at the nodes of an 
achromatic reticulum (figs. 8, 9). In ova of free medusz 
these granules become deeply stainable (fig. 10). 
The oogonia that do not develop into ova are practically all 
absorbed into the substance of the ovum; before tls takes 
place their nuclei fade away (fig. 2), and lose their identity in 
a manner which | could not determine. Though in the later 
stages oogonial cells not in process of fusion with the oocyte 
may exhibit a homogeneous nucleus (fig. 7), yet the nucleolus 
in these stains deeply to the last. In three ova, belonging 
to just liberated meduse, J have observed the nucleus of one 
of these cells persisting in the cytoplasm (fig. 10). The 
nucleolus appeared to be broken down into smaller granules. 
A few similar nuclei could be observed in the vacuoles of the 
manubrium (fig. 10). 
The early stages in the development of the Coelenterate 
egg have formed the subject of a memoir by ‘Trinci (’06), 
wherein he describes several types, and gives an exhaustive 
discussion of the work that has been done in this direction 
up to the present. Prior to the growth of the egg it would 
seem that many ccelenterates reveal a synapsis stage, that is 
to say, the reticulate nucleus is converted into a closely 
coiled spireme, which Maas (’97) found resulted from the 
union of distinctly double chromosomes in the case of Peri- 
phylla and Atolla. The chromatin thread then breaks up, 
as growth commences, into numerous strands, which may 
practically disappear, except here and there alongside the 
nuclear membrane (Phialidium), or which may persist 
