Spermatogenesis iu spiders. 525 



we have constantly recurring shapes for the autosomes and after a 

 little study one may identify the individual chromosomes with ease. 

 Especially is this true of the accessory chromosome. 



After lying- scattered through the nuclear cavity for a time, the 

 chromosomes are drawn into the spindle of the first maturation 

 division. The autosomes are larg-e and have characteristic shapes 

 while the accessory chromosome lies on one side of the spindle 

 (Figs. 33 or 34). The shape of the accessory chromosome is of especial 

 interest in Maevia vittata as it may either appear as a single bivalent 

 body (Fig. 33) or as made up of four elements (Fig. 34). 



Seen from equatorial view, the autosomes have the appearance 

 shown in Figs. 35, 36 and. 37. The varying form of the accessory 

 may best be seen in such a view. In the cell shown in Fig, 35, we 

 see that the accessory chromosome is made up of four elements, two 

 of which are much larger than the others. In Fig. 36 the accessory 

 chromosome has the simple two rod form. And in Fig. 37 the acces- 

 sory is made up of two unequally sized elements. 



M e t a p h a s e. The accessory chromosome goes undivided to one 

 pole very early and the small bodies attached, when present, go 

 with it (Figs. 33, 34). The division of the autosomes follows. It may 

 occasionally happen that one pair of autosomes divides earlier than 

 the rest, as is shown in Fig. 38, but such cases are rare. 



Telophase. Fig. 39 shows a typical late division stage for 

 Maevia vittata. Here the accessory chromosome is conspicuous be- 

 cause of its size and its position. Later we find the cell wall of 

 the two daughter second spermatocytes forming and then they sepa- 

 rate completely. 



Second maturation division. 



The changes through which the chromosomes of the second 

 spermatocyte cells pass, from the late telophase of the preceding 

 division to the formation of the spermatids, are so rapid that it 

 has been difficult to follow them in a detailed way. Immediately 

 after the telophase of the first maturation division, there is a very 

 well defined resting stage (Fig. 40). Here we may see that the auto- 

 somes have become resolved into a faintly- staining reticulum, while 

 the accessory chromosome persists as a nucleolus. The autosomes 

 of the second division are reconstructed from this reticulum; a typical 

 spindle is shown in Figs. 41 or 43. 



Since the accessory chromosome passed undivided to one pole 



Zool. Jahrb. XXXVIII. Abt. f. Anat. 35 



