Spermatogenesis iu spiders. 537 



during a period of five months, the testis shows many division stages 

 for both the first and second spermatocytes. This fact is of unusual 

 interest, for usually in spiders, the males mature and then function 

 sexually, for only a short time. 



Spermatogonia! stages are rare or entirely lacking from the 

 material. During the growth period the accessory chromosome 

 usually appears as a densely staining mass lying on one side of the 

 nucleus, while the autosomes go through their changes. 



In the first maturation division (Fig. 65) the accessory chromo- 

 some usually appears as a bent rod (marked „A") which does 

 not show a transverse split at this time. It goes undivided to one 

 pole during this division and as it approaches the centrosome it 

 bends in such a way that it appears as two rods. The spindle 

 thread attachments seem to be in the middle of the rod. 



There are planosomes (Fig. 66 P), but it has not been possible in 

 this material to follow their behavior or their ultimate fate. A 

 casual glance at the spermatids, however, shows that they are very 

 irregularly distributed. No ctetosomes have been found. 



In equatorial view (Fig. 66) twenty-one autosomes were counted. 

 This count has been verified on a number of other cells. Judging 

 from flat equatorial plates it seems probable that the haploid number 

 of autosomes is about twenty-one. On this basis the chromosome 

 formula would be as follows. 



Autosomes 42 



Accessory chromosomes 2 



Total 44 excluding the supernumerary 

 chromosomes. 

 No attempt has been made to give the spermatogenesis of this 

 primitive form in detail. It seems wiser to reserve this for another 

 paper when more material will be at hand for comparison. 



Spermatogenesis of Amaiirohius sylvestHs, 



Maevia vittata represents a highly specialized spider and in a 

 comparative study it becomes necessary to examine a more primitive 

 type. For this purpose I have chosen Amaurohius sylvestris, which 

 as a member of the family of Dictijnidae, is our lowest northern form. 



My studies on this form have been made on three specimens, one of 

 which was preserved in Bouin's fluid and the other two in Petrunke- 

 vitch's sublimate. The behavior of the autosomes is so closely 



