63 
the uterus; then, just before the metaphase of mitosis, the spindle 
broke down and the nucleus returned to a resting condition. This 
same nucleus later gave rise to polar bodies as in the eggs of other 
animals. Similar aborting spindles have been described by Lane (’84) 
in several species of polyclads, by WHEELER (’94) in Planocera in- 
quilina, by Garpiner (’95, 98) in Polychoerus caudatus, by SURFACE 
(07) in Planocera, by Parrerson (712) in Graffilla gemellipara, and 
by Parrerson and Wireman (712) in Planocera inquilina. Parrerson 
and Wireman have given the uterine spindle in Planocera careful study, 
and have established the fact that in this species it is simply a matu- 
ration spindle which forms near the center of the egg and later 
moves to the periphery, undergoing during this migration a distinct 
contraction. They further suggest that the uterine spindles described 
in the eggs of other animals are really one phase in a typical matu- 
ration process. 
It has thus been shown that the first maturation spindle in 
certain eggs may remain practically inactive for a considerable period. 
It should be noted, however, that in Copidosoma the spindle arises 
not in the fully grown egg but in very young oöcytes, and that it 
appears to lack asters at every period of its history. While, there- 
fore, this structure may be a precocious maturation spindle it differs 
markedly from any other such spindle that I have been able to find 
described in cytological literature. 
The second view is that the odcyte spindle represents a special 
mechanism leading to an accurate distribution of chromatin in the 
keimbahn-chromatin mass. The position of the contracted and con- 
densed spindle, however, is not definite, since it has been found to 
occupy almost any part of the odcyte and to lie with its long axis 
of the oöcyte, or oblique er even perpendicular to this axis (Figs. 7, 
9, 11). Furthermore the keimbahn-chromatin does not seem to be of 
definite structure, but soon after it reaches a sphere-like shape it 
begins to vacuolate and becomes irregular (Figs 13, 15, 16, 17, 18). 
It also seems probable that in some oöcytes the oöcyte spindle gives 
rise to keimbahn-chromatin, whereas in others it becomes disorganized, 
forming the nucleus of the egg (Figs. 15, 16, 17). What causes the 
difference in the history of the oöcyte spindles? No definite answer 
can be given to this question, but there are two possibilities, (1) 
external and (2) internal influences. It seems very improbable that 
any internal mechanism exists which determines what the history ot 
