324 MARGARET C. MANX. 



into one or two rather than into many masses. 1 When few nuclei 

 are present they tend to occupy the center of the egg. Eggs 

 containing resting nuclei were lower in the oviduct than any 

 of the eggs containing spindles, hence it is probable that spindles 

 never form following the disintegration of the second polar 

 spindle in tubal rat eggs. Newman ('13) interprets his atretic 

 armadillo material as indicating that new mitotic figures with 

 asters form following a return to the resting condition after the 

 failure of the second polar division, but none of the rat eggs with 

 central spindles showed any indication of astral radiations. 



There is no indication in the rat material that fertilization by a 

 polar body ever occurs. The first polar body is completely 

 separated from the egg before ovulation takes place. 



Fragmentation occurs almost independently of the newly 

 formed "nuclei," so that some of the resulting cells contain nuclei 

 and some do not. Newman ('13) and Charleton ('17) describe a 

 similar cutting off of anucleate portions of the egg and consider 

 it as a form of deutoplasmolysis. Newman believes that such a 

 process would be advantageous to a cell system governed by a 

 haploid nucleus. Since in the rat eggs the distribution as well as 

 number and size of the "nuclei" is haphazard in the fragments it 

 seems improbable that the process should be considered normal. 

 In the tubal rat material it appears that the fragmentation 

 process is less abnormal when few nuclei are present in the egg, 

 and that it may at times be fairly normal is indicated by the fact 

 that a few normal-looking 2, 3, and 4 cell stages were found. In 

 his observations on unfertilized eggs of Toxopneustes Wilson 

 ('oi) states that most of the blastomeres resulting from a simul- 

 taneous cleavage of syncytia contain nuclei but that some do not. 

 Here also the fewer nuclei present, the more normal the division. 

 Thus in tubal rat eggs as in artificially parthenogenetic one>, .1 

 few may have more vitality than the rest, and these may possibly 

 be considered as possessing a very limited parthenogenetic 

 capacity. 



In the lowest portion of the oviduct all of the ova were obvious- 



1 The possibility that sperm may live in the oviduct for several days and then 

 be capable of fertilization should, however, be taken into c<mM<ln.iti<>n in inti-i- 

 prcting these occasional normal looking cases. \ViU>n (,'oi) also found some un- 

 fertilized eggs which resembled fertilization stages. 



