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SOME PROBLEMS OF COELENTERATE ONTOGENY De 
yet intact; and in some cases, at any rate, the entire fragmenta- 
tion, or dissolution of the nucleolus may occur before the nuclear 
membrane disappears. In other cases nucleolar dissolution and 
disappearance take place coincident with the nuclear dissolution 
and maturation, as stated in a preceding section. In some in- 
stances the nucleolar degeneration seems to involve a gradual proc- 
ess of shrinkage, probably by solution or absorption by the nucleo- 
plasm. It has been no part of my present purpose to study the 
matter of nucleolar genesis, or the possible relation of nucleolar 
metabolism to the genesis and differentiation of chromosomes. 
An interesting and varied literature on this subject has grown 
up with recent times, some of which seems to have a profound 
significance in relation to chromosome theory. But to enter 
upon this phase would involve time and details far beyond the 
scope of the present paper. 
5. Later development. It is not the purpose to enter into any 
considerable details as to later aspects of development save as 
they are found to be more or less exceptional as compared with 
other species concerned. As to cleavage no occasion has been 
found to modify the account already given in the former paper 
(pp. 223 to 227). There is much here in common with that 
known in Tubularia, Hydractinia and Pennaria. While in a 
certain proportion of the eggs cleavage is more or less regular; 
on the other hand, in a large proportion, irregularity and lack of 
order or symmetry is the rule. This is particularly the case with 
those ova which are flattened laterally against the sides of the 
spadix of the gonophore. In the case of ova terminally placed 
in the gonophore the shape is more nearly spherical, and in such 
cases the tendency is toward regularity. This is what one might 
naturally expect; yet there are notable exceptions, and one will 
do well to remember the extremely erratic cleavage of such ova 
suggested in a following sentence, I am not prepared to suggest. The nucleus of 
this egg was in rather typical resting condition, and its chromatin of the usual 
granular spireme aspect. As stated in another connection, different modes of 
fixation and staining have appreciably different effects on the egg cytoplasm and 
nucleoplasm, so that much more elaborate observations would be necessary ere 
one might venture any very positive opinions on so complex a problem. 
