96 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Groom correctly described the radial arrangement of the protoplasm 
as persisting for some time after cleavage. In my Figure 27 there is 
represented a radial arrangement of granules which is a persistence of 
the condition shown in Figure 26 as occurring at the close of the first 
cleavage. The astrospheres have disappeared, and the nuclei lie near 
the centres of the persisting radiations. This radial arrangement dis- 
appears as soon as the second cleavage spindle forms (Fig. 28), but the 
new radiations then formed may in turn persist after the cleavage until 
the formation of the spindles for the third cleavage (Fig. 30). 
Groom (’94) states that two or more blastomeres may arise simule 
taneously from the yolk-cell! ‘Similar cells [blastomeres from the 
yolk-cell] are seen to arise in quite different positions at later stages, 
sometimes two or more at a time,” (p. 138). Again, on page 140 he 
writes: “ In the early as inthe later stages the merocyte before emerg- 
ing from the yolk may not uncommonly be seen to give rise by division 
to a second merocyte.” Such conditions are represented in Groom’s 
Figures 17a (L. anatifera), and also in his Figures 53 and 57 (Balanus). 
Certainly none of these figures really represents two blastomeres arising 
at once. The two sets of radiations (asters) which Groom wrongly 
interpreted as two “emerging merocytes” probably represent cases in 
which the spindle was in such a position that both asters were visible 
at the surface. Usually, however, only one aster is to be seen in the 
living egg, the other being closely connected with the yolk. Sometimes 
the spindle is long, so that the two asters are visible on opposite sides 
of the egg. I have frequently seen the two sets of radiations in the 
living egg, and sections show that the interpretation which I have just 
given is the correct one. 
Sometimes multipolar spindles, which are probably the result of 
abnormal conditions, are seen in sections of the yolk-cell, and these may 
possibly result in a multiple cleavage. 
Rarely the cell c®? (Groom’s “second blastomere”’) may be formed 
near the posterior end of the yolk-cell, as shown by Groom in his 
Figure 13. 
Many other deviations from the regular course of cleavage have been 
seen, but they are comparatively rare, and are to be regarded as abnor- 
malities. Certainly they should not be interpreted as showing great 
variability in the cleavage, as was done by Groom. I have noticed that 
such cases are much more common when the animals have been kept 
for some time in aquaria, but are rarely seen in eggs taken from ani- 
mals which were recently removed from the open sea. I have attributed 
