2oS KINGSBURY. [\oi.. II. 



from the standpoint of the more typical mode of reduction by 

 tetrad formation with longitudinal and transverse divisions, 

 there would occur in Dcsuiogiiathns a reduction in number to 

 one-half, a longitudinal (equation) division, followed by an 

 attempt at a second longitudinal division, which, however, is 

 not completed, and is prevented from being completed, by the 

 second division, which is transverse, ^x. Shorten the inter- 

 val elapsing between the first and -h^ \ second divisions, 



and (possibly thereby) eliminate the ^-^ second longitudi- 

 nal splitting, and the process is reduced to the typical form. 



r It seems to the writer, however, far more likely that 



L J. both divisions in Dcsi/iog?iat/iiis are equation divisions, 



^-^ in agreement with the results of Brauer, Hertwig, 

 Moore, Meves, and the majority of the botanical workers. 



There are two or three interesting comparisons that may be 

 made between the first and second divisions of the spermato- 

 cyte. In the period of growth to form the spermatocyte of the 

 first order the chromatin segments form loops or U's with the 

 open end toward the centrosphere and centrosome (Fig. i). In 

 the spermatocyte of the second order, on the other hand, the 

 apices of the F's are toward the centrosome. In the longitu- 

 dinal division of the segments in the spermatocyte of the first 

 order the free ends of the segments remain united (or fuse 

 after separating), forming rings. In the spermatocyte II 



the apices (opposite ends of the / \ joined chromosomes) re- 

 main united, and the correspond- ing figure in the second 

 division is a cross. The chromatin in the two divisions is 

 thus contrasted in >< these two particulars, to which it is 

 felt some impor- tance may attach. 



In Desmognat/nis, therefore, there are two divisions interven- 

 ing between the last spermatogone division (as so determined) 

 and the spermatid, in both of which occurs longitudinal split- 





Fig. 5 



