Spermatogenesis iu spiders. 549 



upon by Berey (1906), and I can confirm in detail the description 

 of that author. There are a few points not described by Berey, 

 which are of interest to us in the present comparative study. 



The rest period of the young primary spermatocytes can be 

 seen in all of the slides although Beery failed to find it in her 

 preparations. During the synaptic contraction we have a very 

 striking behavior on the part of the accessory chromosome. It 

 usually lies free in the nuclear cavity entirely apart from the con- 

 tracting leptotene-threads. And in the second contraction (Fig. 91) 

 it shows the same behavior. Here the early appearance of the centro- 

 some is also shown. 



During the first division tlie accessory chromosome (Fig, 92) is 

 made up of two elements and these pass undivided to one pole 

 early in the division, as described by Berey. During the second 

 maturation division the accessory chromosome divided and, as a 

 result, half of the sperm carry the accessory chromosome and half 

 lack this body. 



Chromosome counts have not been made in this form, but Berry's 

 count would indicate the following: 



Autosomes 22 



Accessory chromosome 2 



Total 24 



It should be stated that Berey derived the accessory chromo- 

 some from one spermatogonia! chromosome; but from a study of other 

 forms, it seems probable to me that she was mistaken in this. I 

 regret to say that my material was too mature to allow a study 

 of this point on the same form used by Beeey. 



Spermatogenesis of Xt/stieus trif/uttatus. 



As a representive of the family of Thomisidae - the Crab- 

 spiders — this common species has been studied. This spider matures 

 about the middle of May, at New Haven, and it may be caught in 

 unlimited numbers by "sweeping" grass and flowers with a fine- 

 meshed net. 



First maturation division. 



The rest period presents one point of interest shown in Fig. 93. 

 Here we find, in addition to the accessory chromosome elements, a 

 very small body, marked "P". During the growth period this body 



