160 W. H. LONGLEY 



cannot be definitely denied, the most that can be said with regard 

 to number after the study of this spindle alone is that the individ- 

 ual tetrads are not less thantweh e nor probably more than sixteen. 



The second of the two spindles in question (fig. 5, C) is nearing 

 the telophase of division and more crowding and overlapping 

 of the chromosomes has occurred. Nine distinct masses of chro- 

 matin appear which were destined to have been eliminated in 

 the first polar body. At the central pole of the spindle there are 

 corresponding elements not quite as clearly individualized which 

 would have furnished the chromatic portion of the second polar 

 spindle. Farther study makes it clear that the first group includes 

 certainly not less than twelve dyads. The second group strongly 

 suggests that there are thirteen including a lagging heterochro- 

 mosome. 



The counting of the chromosomes in the last spindle described, 

 therefore, greatly strengthens the hypothesis that twelve is the 

 number of tetrads in the cat's egg. This idea must be modified, 

 however, for in the first of the two there are eight bits of chroma- 

 tin which are much smaller than the others, and in addition 

 vary among themselves in size. That ihey are not fragments 

 without significance appears from the definiteness with which 

 they are paired. They represent eight individual dyads. Upon 

 making a comparative study of these two spindles the one in the 

 telophase of division shows at once two pairs of chromosomes 

 which in size and shape correspond to the larger two pairs of the 

 four of the first of the two spindles now being discussed. There 

 is also a small, linear, chromatic element at each pole which from 

 its size, shape and position it is perfectly justifiable to interpret 

 as representing two very small chromosomes in apposition. 



Thus the comparison of these two spindles gives some evidence 

 in favor of an individuality of the chromosomes, although there 

 seems no possibility of carrying very far the pi'ocess of identifi- 

 cation of individual chromosomes in different spindles. The 

 point to be made in this connection is that fourteen becomes the 

 minimum number of tetrads in the cat's egg. In fact, one might 

 say that fourteen is probably the number of tetrads in the egg 

 of this animal, if it were not that the uncertain evidence from the 



