PAIRING OP TE&ENARIA. GUTONII. 171 



instinct. By that time, when in a free state, other attractions, if 

 not his wandering disposition, would take him away from the 

 web. Even if he again approached her, and sh.e were the weaker, 

 there would be ample opportunity for an escape by the lower 

 tube of her cob, as collectors know to their loss. So long as the 

 females are not injured, the benefits to the species, both in size and 

 strength, are obvious when males capable of effecting more than 

 one impregnation are sufficiently powerful to prevent an attack. 



The Eev. O. P. Cambridge (Proc. Zool. Soc. 1871, p. 621, see 

 also ' Descent of Man,' p. 273, 2nd ed.) ascribes the extreme 

 smallness of the male in the genus Nephila to the chances of 

 escape from the female beiug in favour of a diminutive race of 

 males. This at first sight appears antagonistic to tbe opinions I 

 have advanced ; but natural selection will have effected different 

 degrees of correlation between agility and size according to the 

 habits and early form of the species. 



Our Secretary Mr. E-omanes ('Animal Intelligence,' p. 205) 

 has referred to these sexual conflicts, and suggests the courage 

 and determination required of the male may be of benefit to the 

 species by instilling these qualities into his descendants. I would 

 add that the capture or escape after union of males capable of 

 effecting more than one impregnation would develop agility and 

 strength ; for those which were maladroit or weak would be 

 eliminated. The attack by the female would also be of specific 

 advantage, for it is but another form of that vigour which is so 

 profitably directed against the larger kinds of prey. 



Certain Organs in the Male Abdominal Sexual Eegion. 



The external abdominal sexual region is marked by a slight 

 convexity, in front of which is placed transversely a row of trans- 

 parent spines (fig. 7, S S) . Two papilla-like processes are situated 

 just above the opening of the ejaculatory duct* (fig. 7, P, P*). 

 Neither of these organs have hitherto been noticed. 



* Each vas deferens opens into a sinus which passes backwards and down- 

 wards, and unites with its fellow to form a common chamber in front of the groove 

 traversing the ventral surface of the abdomen between the openings of the pul- 

 monary sacs. The chamber opens out on the anterior portion of the groove in 

 a transverse slit. Fig. 6 represents diagrammatically, in section, the position 

 and course of the vas deferens, sinus, and opening. The incomplete function 

 the chamber which unites the two sinuses, as compared with that of other homo- 

 logous male sexual organs, seems to render the word penis inapplicable to it. 

 I propose to employ the term ejacidatory duct to the chamber. 



