SPERMATOGENESIS OF LEPISMA DOMESTICA 407 



In the first place, the general shape and arrangement of the 

 chromosomes in the spermatogonia of Gryllotalpa borealis are 

 very much like similar stages in Lepisma domestica. Payne 

 also has described changes in the mitochondrial mass of the 

 spermatid (his figures E, F, and G, pi. 2), which have almost 

 exact counterparts in Lepisma domestica. Then again his 

 figure J on plate 3 shows an axial filament in which the cytoplasm 

 is so arranged in waves as to look like the undulating membrane 

 found in the Thysanura. 



A comparison of the group of chromosomes associated prob- 

 ably with sex in the two forms shows, however, several important 

 differences. In Gryllotalpa borealis Payne finds a single chromo- 

 some which does not divide in the first maturation division and 

 therefore could be directly compared with the idiochromosomes 

 of the Thysanura were it not for the fact that the single chromo- 

 some is associated with an unequal bivalent chromosome and in 

 division always goes to the same pole as the large 'end' of the 

 unequal chromosome. Therefore, the two resulting secondary 

 spermatocytes differ not only in that one has an extra 

 chromosome, but also in that the same cell possesses the large 

 'end' of the unequal chromosome, while the smaller part passes 

 to the other cell. Payne favors the view that these chromosomes 

 represent a triad group rather than an unequal pair of idiochro- 

 mosomes and an accessory chromosome. 



Payne has not been able to trace the centrosome of the second 

 maturation division through to the spermatid, and in fact has 

 not been able to demonstrate the presence of the centrosome in 

 the spermatid at all, although he presumes that the body from 

 which the axial filament arises and which later becomes the 

 middle-piece may be a centrosome. Further, he describes the 

 acrosome as arising from an elongated body which suddenly 

 appears de novo in the cytoplasm, whereas in Lepisma domes- 

 tica the acrosome is formed from a rod-like centrosome. 



JOURNAl, OP MORPHOLOGY, VOL. 35, NO. 2 



