SOME PROBLEMS OF COELENTERATE ONTOGENY Sit 
Bouin’s picro-formol, and in Zenker’s solution, and carefully 
stained by several of the most recent methods. So far as it 
relates to the organization of the egg or its cleavage no occasion 
has been found for modifying in any essential the earlier conclu- 
sions. These I believe to be confirmed in every detail, and lead 
me to reaffirm the former account. Concerning some few points 
in relation to the phenomena of maturation and nuclear behavior, 
including phases of germ-layer formation not touched upon in 
the previous paper, it is necessary to reconsider and add to the 
former results. 
1. Maturation. Concerning the phenomena associated with 
maturation my observations will be very brief. In the former 
paper the general facts were explicitly stated and no occasion has 
been found to call for essential modification. Both in living eggs 
and in sections of stained material polar bodies were found and 
described. In connection with earlier accounts of this feature 
in other eggs of hydroids one may find such expressions as “‘ About 
this time the nucleus becomes indistinct and finally disappears;”’ 
the nucleus ‘‘fades from view when the ovum is deposited.” 
These accounts relate almost wholly to observations upon living 
eggs, and I have repeatedly verified them both in the living, and in 
sections of fixed eggs. While in themselves such accounts may 
seem to have little of distinctive value, in a morphologic sense, 
yet, as expressive of physiological conditions they seem to me to 
have very large significance. In the first place, these observa- 
tions described what was actually seen and its fidelity to fact can 
not be questioned. In the next place, cytological study of fixed 
material confirms just these accounts. As eggs grow toward 
maturity the germinal vesicle is large and conspicuous. But as 
they approach the phase of metabolism involved in maturation 
a marked change occurs, as is well known. The chromatin 
network, which has been conspicuous, gradually disappears, 
and in many cases loses absolutely its affinity for stains. With 
dissolution of the nuclear membrane, a still further change occurs, 
which is exactly what these accounts describe, namely, the min- 
gling and fusion of nucleus and cytoplasm to such a degree that it 
is often difficult to differentiate them by any of the usual methods. 
