504 M. D. AIL. 
of the nucleus. This occurs in many Ciliates. For instance : 
In ‘ Oxytricha and Lacrymaria’ Gruber has shown that the 
meganucleus breaks up into minute fragments which become 
scattered through the protoplasm, but eventually reunite into 
a single body. 
So much attractive speculation has been based on the 
ordinarily observed facts of maturation and fertilisation that 
we feel almost bound to assume that these processes are the 
same in all metazoa. But it is obvious that in certain ccelen- 
terates we have facts before us that cannot be brought into 
line with what we feel we have a right to expect. At 
present the affair is a mystery. Pending further investiga- 
tion it were unwise to speculate on the possible meaning of 
these phenomena, however much one may be tempted to do 
so. In case that what I have observed, and still more failed 
to observe, may induce some other zoologist to follow this 
cytological byeway, I can only hope that he will find this 
paper a path over which it may not be necessary to retrace 
his steps. There would seem to be four points to which 
attention should be specially directed: 
(a) The nuclear history of the germ-cells from their earliest 
“ Anlagen.” 
(b) The mode of formation of the polar bodies. 
(c) The actual penetration of the spermatozoon. 
(d) The way in which the first segmentation nucleus is 
built up. 
Lastly, I have but to express my sincere thanks to Professor 
Hickson for his kindness in allowing me the use of his 
material, preparations, and notes, and for the many fruitful 
suggestions that I have received from him. 
ADDENDUM. 
Since writing the above my attention has been drawn to 
another paper by C. W. Hargitt, viz. “ Notes on the Hydro- 
medusz of the Bay of Naples,” ‘ Mith. Zool. Stat. Neapel.,’ xvi, 
4, p. 562. Writing of Pachycordyle Weismanni, Hargitt 
