536 Theophilüs s. Painter, 



elements represent the accessory chromosomes; and the number indi- 

 cates that two meausures are present in the female, one dose con- 

 sisting of two rods, as has been shown to be the case for the males. 

 These results have been checked by examining dividing gland cells 

 of four females and the conclusion is the same in every case. In 

 Fig. 64, we have an equatorial plate of a dividing cell taken from 

 two adjoining sections. Although there is much over-lapping one is 

 able to count 29 chromosomes in this cell. If we exclude any super- 

 numerary elements, we should expect thirty chromosomes in such a 

 view, since the diploid number of autosomes is twenty-six for the 

 male, as has been shown above, and there being four chromosomes 

 in the two doses of the accessory which the female should carry. 



These observations bring the spiders into line with the recent 

 work on many other forms of invertebrates, particularly the Hemi- 

 ptera. Through the work of Wilson, it has been demonstrated that 

 the males may carry only one accessory chromosome. The bearing 

 this discovery has on the problems in heredity, especially on sex- 

 linked inheritance, is too well known to call for any discussion here. 



It should be noted that in all of the females studied, indications 

 of small chromosomes were found, presumably supernumeraries, but 

 it has not been possible to follow the behavior of these bodies in 

 the dividing gland cells. 



The observations given above make it reasonably certain that 

 the females carry two measures of the accessory chromosome, yet 

 there are many interesting questions that would be solved by a 

 study of the oogenesis of spiders. The author has collected material 

 for this end and hopes to complete this chapter in the history of 

 the germ cells of spiders in the near future. 



Speriiiatogenesis of Duf/esiella hent^i. 



Dugesiella lienfzi, as a member of the family of Avicularidae (the 

 tarantulas), represents one of the most primitive forms studied up to 

 the present time. The specimen studied was a fully mature male 

 which Professor Petrunkevitcii had under observation during a 

 period of five months. At frequent intervals, this male was allowed 

 to mate with females. Professor PETKUNKEvrrcn ('11) has described 

 the mating habits and the natural history of this little known family, 

 in a very interesting paper. 



Although this specimen copulated with females at intervals 



