Spermatogenesis in spiders. 567 



we can accept this for spiders as has been done for so many other 

 forms. However, this has not been proved by direct observation. 

 Whether the leptotene-threads pair end to end or side by side, I 

 have not been able to determine. 



After the sjaiaptic contraction, the pachytene-threads appear in 

 the nuclear cavity with a "bouquet form". Both Montgomery and 

 Wallace claimed to have been able to see where the two leptotene- 

 threads were joined end to end in these pachytene-threads. I 

 have never been able to see this in any of my preparations, and 

 aside from ^appearing somewhat irregular in outline, no swellings or 

 breaks have been seen in the threads. 



A longitudinal split appears in the pachytene-threads soon after 

 they have emerged from the synaptic contraction. This split may 

 persist until the earl}" prophase, and in Dolomedes fontaniis, each of 

 the two daughter autosomes which go to the two poles of the 

 spindle, in the first division, crvvj this split. In other words, one 

 half of the length of the split diplotene-thread goes to one pole 

 and the other half to the other pole. If we regard this longitudinal 

 split as separating the two conjugating leptotene-threads, then the 

 first division in spiders is a simple equation division. If, on the 

 other hand, we hold that end to end pairing has taken place, as 

 was claimed by Montgomery and Wallace, then the first division 

 is the reduction division, and the longitudinal split has no signi- 

 ficance as regards reduction. 



Dimorphism of the males of Maevia vittata. 



Discussion of this question has been delayed until now in order 

 that we might have before us the facts obtained by a study of other 

 families of spiders. The difference which appears in the spermato- 

 genesis of the two types of males has been given in the foregoing pages, 

 so we need only to summarize the facts here. It has been shown 

 that the gray variety carries two ctetosomes. The tufted variety 

 carries no ctetosomes but we may find a planosome present. In the 

 present discussion I wish to point out the possible bearing which 

 this may have on the dimorphism of the two forms. It should be 

 emphasized, however, that this discussion is based upon cytological 

 evidence and that up to the present time, I have not been able to 

 test out the conclusions in an experimental way. This I hope to 

 do in the near future. 



In looking for a cytological basis of the dimorphism found in 



