86 HELEN DEAN KING. 



Carnoy and Lebrun find a double division of the chromosomes 

 in the egg of Triton, and they state that there is no reason why 

 a longitudinal division of the chromosomes should not be a 

 reduction division in the Weismann sense, in that it may separate 

 the chromosome into two parts each containing different kinds 

 of granules : it is certainly true if we admit a difference in the 

 properties of the elementary granules. As all of the chromatin 

 granules do not go into the chromosomes of the first polar spin- 

 dle, there is a process of selection in the formation of the chro- 

 mosomes and their subsequent division would be a permanent 

 source of variation for the descendents. 



The chromosomes of the first polar spindle in the egg of Bnfo 

 Icntiginosits are at first exceedingly varied in shape ; they may 

 be round, triangular, or oblong. At this time it is obvious that 

 they have no definite longitudinal axis. At the stage of Fig. 5 the 

 chromosomes have elongated and lie parallel with the longitudinal 

 axis of the spindle. When the wings have formed, there is a 

 stage when the arms of the chromosomes are all approximately 

 of the same length (Fig. 6). Is there a definite longitudinal axis 

 at this time ? If the part of the chromosome resting upon the 

 spindle fibers is considered to be the longitudinal axis, then later 

 this same axis is not only shorter than the transverse axis, but 

 it practically disappears at the stage of Fig. 9. If shown Fig. 9 

 without the preceding figures, no one, I am sure would call the 

 thickness of the chromosome at the an^le of the V the longi- 



o o 



tudinal axis of the chromosome, and the division indicated in 

 Fig. 1 1 would unhesitatingly be called a longitudinal division. 

 If one arbitrarily states that the polar arms of the chromosomes 

 in Fig. 5 form the true longitudinal axis, not only in this par- 

 ticular stage, but until division is completed, then the splitting 

 seen in Fig. 1 1 is a transverse division, as is also the second 

 division which takes place in the same direction. On the other 

 hand, if the longer axis of the chromosome at the time when 

 division occurs is considered to be the true longitudinal axis, 

 then there is a double longitudinal division of the chromosomes 

 and the egg of Bnfo is thus brought into line with other amphib- 

 ian eggs that have been studied. It would seem, as suggested 

 by Sebaschnikoff (14), that the distinction between transverse 



