510 Theophilus s. Painter, 



IV. Discussion. 



1. Irregularities. 



2. Origin and behavior of the accessory chromosome. 



3. Determination of sex in spiders. 



4. Origin and behavior of the ctetosomes and planosomes. 



5. Autosomes. 



6. Dimorphism in Macvia vittata. 



Introduction. 



Since 1909, when Wallace published her complete description 

 of the spermatogenesis of Agalena naevia, no work has been done 

 on the germ cells of spiders, although few forms of invertebrates 

 afford such an attractive field for cytological investigation. Prior 

 to the appearance of Wallace's complete paper, comparatively little 

 work had been done on the spermatogenesis of the true spiders. 

 The earliest paper was that of Caenoy in 1885. This author des- 

 cribes in detail the division of the male germ cells for a number of 

 forms, but his work has no direct bearing on modern spermatogenesis, 

 because, at that early time, cytologists did not recognize the sequence 

 of changes through which the germ cells pass in maturation. The 

 works which have been done with sufficiently modern methods to 

 be of value to us, are those of Wagnee (1896), Wallace (1900, 1905, 

 1909), BÖSENBEEG (1905), MoNTGOMEEY (1905) aud Beery (1906). 



Montgomery published his account of the spermatogenesis of 

 Lycosa insopita in 1905, but although his observations were made 

 with great care, his interpretations were open to some question as 

 pointed out by Wallace (1909). Montgomery describes the acces- 

 sory chromosome in this form as arising from two spermatogonial 

 chromosomes, but he did not trace the course of this body through 

 the maturation divisions. 



The work of Bösenbeeg deals almost entirely with the trans- 

 formations of the spermatids into tlie mature sperm and, tlierefore, 

 does not directly concern us in the following paper as no attempt 

 has been made to follow the changes going on in the spermatids. 



Berey, working on Epeira sclopetaria, was the first to trace the 

 course of the accessory chromosome through the maturation divisions. 

 She showed that the accessory body passed undivided to one pole 

 of the cell during the first spermatocyte division and was equally 

 distributed in the second. She derived this body from one spermato- 

 gonial chromosome. 



