134 THE VOYAGE OF H.M.S. CHALLENGER. 



with the wall of the leg. The one part is filled up with the ovary, the other partlj- with 

 the coeeum of the intestine. The ovarian eggs are small and are furnished with a 

 central germinal vesicle. Most probably the females of the species of Ascorhynchus have 

 an oviduct like that of the species of Colossendeis. The species of Pcdlene show the same 

 disjjosition as in Nymphon. A transverse section of the thigh of Pcdlene australiensis 

 corresponds perfectly with that of Nymphon hrevicaudatum, figured in Plate XVI. 

 fig. 7 ; there is one very large and probably mature egg with an eccentric germinal 

 vesicle, and numerous smaller ovarian eggs, with their vesicle in the centre. Moreover, 

 minute researches on Pcdlene hrevirostris (an inhabitant of the Dutch coast) admit of no 

 douljt as to the structure of the ovaries ; they are totally wanting in the body, and take 

 their origin in the thighs of the legs. The eggs when mature are large, and their number 

 is limited. 



In the genus Phoxichilidimn I studied the anatomy of the body of Phoxichilidium 

 pdosum (a female specimen) without meeting with the. ovary. In the legs of this 

 species, however, and also of PhoxichUidium patagonicum, I soon found it. The 

 whole cavity of the leg is often filled up with eggs, and these are even observed 

 pressed closely against the wall of the leg (PI. XVI. fig. 17). The eggs are comparatively 

 small and very numerous. The membrane of the eggs is much thicker than is the case 

 with the eggs of the other genera (PI. XXI. fig. 18). Neither in the species of Pcdlene 

 nor of Phoxichilidium did I observe the least trace of an oviduct, so I think that here, 

 as in Nymphon, the genital aperture communicates directly with the cavity of the leg. 

 I think also that the circumstance I often observed of eggs free in the cavity of the 

 leg is in suj^port of this opinion (PI. XXI. fig. 18). For the other genera of Pycnogonids 

 I have, so far as the ovaries are concerned, no observations worth mentioning. 



7. Observations on the Embryology of the Pycnogonida. — Among the Pycnogonids of 

 the Challenger Expedition there were some sj^ecies provided with eggs. On account of 

 the great importance of embryology for the study of the aftinities of a group of animals 

 I tried to acquire as much information on this subject as possible. Unfortunately, with 

 the exception of one species belonging to the genus Ascorhynchus, G. 0. Sars, all the 

 species with egg-masses belong to the genus Nymphon, Fabr., but of these there are out 

 of twelve species no less than six provided with eggs. 



The researches of Kroyer, Johnston, Goodsir, Dohru, Semper, Cavanna, and myself, 

 have shown that in the genera Pycnogonum, Pcdlene, Phoxichilus, Phoxichilidium, 

 Nymphon, &c., the eggs after having been laid are carried on the so-called ovigerous 

 legs. The honour of having discovered that not the females (as was believed by the 

 older authors) but the males fulfil the duty of bearing these eggs is due to Cavanna ; this 

 observation has since been confirmed by the researches of Dohrn, Bohm, and myself.^ 



' The observations of Cavanna were published in the year 1875. It is indeed strange to see that neither Wilson 

 nor Miers have heard of this discoverj'. These authors, in their descriptions of new species, &c., are therefore ahnost 

 constantly confounding the two sexes. 



