28 W. S. SUTTON. 



In this case there is plainly a possibility for an exchange of 

 chromatic matter ; but since each generation exhibits the same 

 series of chromosomes as that before ; and since, after the stages 

 of the very fine spireme, the chromosomes reappear one in each 

 sacculation as before, no other conclusion seems credible than 

 that they are, chromosome for chromosome, the same in one 

 generation as in another, just as is the case with the accessory. 



During the transformation to spermatocytes, the nucleus as a 

 whole becomes spherical, but, in many cases, the compartments 

 still remain ; and in them the chromosomes pass through the 

 fine spireme stages. In this condition, as in that just described 

 for the spermatogonia, it is difficult to conceive the formation of 

 a continuous spireme ; but when, at a little later stage, cell and 

 nuclear membranes have become less resistant so that their con- 

 tents may be smeared upon cover-glasses and there fixed for study 

 /;/ toto, it becomes clear that fewer spiremes are present than in 

 the spermatogonial nuclei. In every case, the accessory chro- 

 mosome appears in its peculiar characteristic condition (.r, Figs. 

 5 <?, 5 b, 6 and 7), and careful counting of a large number of cases 

 sJwvs the spiremes in every favorable instance to number eleven. 

 These spiremes are graded as to size just as were the chromo- 

 some-pairs of the spermatogonia ; and the gap in the series sep- 

 arates a group of eight large horn a group of three small elements. 

 In most of the spiremes a longitudinal split is clearly visible, and 

 in addition, in practically every case, a division may be noted 

 separating the spireme into two distinct limbs of approximately 

 equal size, which are frequently doubled on each other at the 

 point of union. 



If now we seek the relation of these spiremes to the chromo- 

 somes of the spermatogonia, we find abundant data. Twenty- 

 two chromosomes enclosed in separate compartments, each open- 

 ing at one end into a common chamber, are represented by eleven 

 double chromosomes. Scarcely any two of the eleven are even 

 approximately of the same size, whereas each of the twenty-two 

 appeared to have a mate of like volume. But the eleven double 

 chromosomes are made up each of two limbs of equal size and 

 we find it difficult to believe that these limbs do not represent 

 the members of the pairs, joined together at their polar ends, 



