XXI INTEGUMENT REPRODUCTIVE ORGANS 519 



many little cavities, some of them conical and tapering to a 

 minute external pore, the others more regularly tubular. Some- 

 times, hut according to Hoek rarely, tlie tubular pore -canals 

 communicate with, or arise from, the conical cavities. The pore- 

 canals transmit a nerve for the supply of sensory hairs, often 

 forked, which arise from the orifice of the canal in little groups 

 of two or more, sometimes in rosettes of eight or nine. These 

 setae are small or rudimentary in Ascorliynclnts and totally 

 wanting in Colossendeis ; they appear to be extremely large 

 and stellate in ParanyTnijhon. The conical cavities contain 

 proliferated epithelial cells, blood-corpuscles, and cells of more 

 doubtful nature that are perhaps glandular. According to Dohrn, 

 glands exist in connection with both kinds of integumentary 

 perforations, and he suspects that they secrete a poisonous fluid 

 in response to stimuli affecting the sensory hairs ; Hoek, on the 

 other hand, is inclined to ascribe a respiratory function to the 

 cavities ; but indeed, as yet, we must confess that their use is 

 undetermined. 



Reproductive Organs.— In each sex the generative organs 

 consist of a pair of ovaries or testes lying above the gut on 

 either side of the heart ; in the adult they are fused together 

 posteriorly at the base of the abdomen, and send long diverticula 

 into the ambulatory legs. In the female Plioxichilidium, at 

 least, as Loman has lately shown, the fusion is complete, and the 

 ovary forms a thin broad plate, spreading through the body and 

 giving off its lateral diverticula. The diverticula of the testes 

 reach to the third joint of the legs, those of the ovaries to the 

 fourth, or sometimes farther. The ova ripen within the lateral 

 diverticula, chiefly, and sometimes {Pallene) exclusively, in the 

 femora or fourth joints of the legs,^ which, in many forms, are 

 greatly swollen to accommodate them ; the spermatozoa, on the 

 other hand, are said to develop both within the legs and within 

 the thoracic portions of the testis. The genital diverticula may 

 end blindly within the leg, or communicate through a duct with 

 the exterior by a valvular aperture placed on the second coxal 

 joint. Such apertures occur, as a rule, on all the legs in the 

 females, in Rhynchothorax and Pycnogonum on the last only. In 

 the males an aperture is present on all the legs in Decolojjoda and 

 Phoxichilidium ; on the last three in Xymphon and PhoxicJrih's; 



^ In the second joint in Ascorhynchus abyssi, Sars, and A. tridens, Meinert. 



