GYNANDRY IN ARACHNIDA. 



By the Rev. J. E. HULL. 



(With one Text-figure.) 



i. I WRITE under the general heading of Arachnida though actual 

 cases of gynandry are known in one order only — Araneae. In the con- 

 cluding section of this paper, however, I shall have something to say 

 concerning the other orders : meanwhile I proceed to discuss the spiders. 



It may be well in the first place to review the general sexual 

 characters, beginning with the external structures of the genitalia. These 

 lie on the median line of the epigaster — the anterior segment of the 

 venter — flanked on either hand by the anterior spiracles. In the female 

 this sexual area is a more or less specialised epigynium, sometimes simple, 

 sometimes elaborately sculptured (affording excellent specific characters), 

 in or under which the vulvar apertures are situated. In the male there 

 is no special epiandrium ; the paired apertures open on the epigastral 

 margin, and Eire practically invisible under ordinary powers of magnifi- 

 cation. There is no penis ; the copulatory apparatus is a sjjecial 

 modification of the terminal article of the palp. 



The outstanding secondary sexual characters are the following : 



1. Size. The female is almost invariably larger than the male, 

 sometimes considerably larger : but none of the known instances of 

 gynandry have occurred where the difference in size is unusually great ; 

 all the records are of species in which the total length of the female does 

 not exceed that of the male by more than 15 per cent, of the latter. The 

 difference is always sufficient to cause asymmetry of the body in the 

 gynandromorph, though in some cases it is not very conspicuous. 



2. Palpi. As the tarsus in the male is expanded and hollowed out 

 beneath to accommodate the highly specialised copulatory apparatus, it 

 becomes an organ of the greatest importance, affording, like the epigyne 

 of the female, excellent specific characters. The ' genital bulb,' as it is 



Journ. of (ien. vii 12 



