SOME PROBLEMS OF COELENTERATE ONTOGENY 499 
son was impossible, though there is no reason for doubt as to 
its subsequent similitude and results. A comparison with figures 
1 to 4, of Pennaria tiarella, will make this more evident. 
The fact that these eggs had been taken with the tow-net 
in the open harbor, and had been preserved shortly after in for- 
malin, leaves no grounds for serious question as to their normal 
condition, and confirms completely the results of my own pre- 
cautions (’04b, p. 474), to guard against possible effects of arti- 
ficial conditions of the laboratory. These additional facts, 
together with others of like character which have since come to 
our knowledge, especially those described by Brooks and Ritten- 
house (07) must suffice once for all to establish the perfectly 
natural and normal phenomenaof extremely erratic and indetermi- 
nate modes of cleavage and consequent organogeny. 
1. Cleavage. ‘There is nothing new to add concerning the 
cleavage features of the eggs of Pennaria tiarella. Concerning 
this feature in Pennaria australis little attempt will be made to 
give detailed descriptions. The figures cited will afford all that 
is necessary as to the general surface aspects. As already stated, 
there is such essential conformity in every respect to the corre- 
sponding stages in Pennaria tiarella that there seems small occa- 
sion to do more than refer to the figures and descriptions of the 
former paper (’04b). While the fixation does not give material 
fit for cytologic details, it is fairly good for general comparisons. 
Eggs carefully stained and cleared show fairly well the general 
internal conditions, and here, as in the surface features, there is 
essential likeness to corresponding stages in Pennaria tiarella. 
2. Nuclear aspects. Brief reference may be made to a few 
points under this head. 
Fragmentation. In several of my earlier papers (’04b, pp. 
460-1), attention was called to certain nuclear phenomena of 
a rather peculiar character. Among these was what seems to be 
a rather promiscuous dissolution, or disintegration of the nucleus 
and the dispersion of the greater portion of it into the cytoplasm. 
To designate this process I used the term fragmentation, long 
previously employed to designate phases associated with direct 
nuclear division, and apparently first employed by Van Beneden 
(Wilson, the Cell, p. 64). 
