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



Ijranchicata. The larvae of different species, as observed by me, usually remain for a 

 long time after having cast off their exuvige, in relation to the ovigerous leg of their 

 parent. As long as they were enclosed in their egg, they clung together tightly enough ; 

 but once crept out of the egg-shell, a special arrangement is necessary to keep them 

 together. This is found in the threads, and the supposed glands from which these take 

 theii' origin, as observed by Dohrn and me. Repeatedly I saw, as I have mentioned 

 already before, between the larvae of Nymphon hrevicoUum, collections of very numerous 

 skins held together by means of the threads, and small parts of such a cast skin I found 

 also in relation with the thread of the larvse of Nymphon longicoxa. 



It is true that the structure of the apparatus, as it shows itself in the larva of Nym- 

 phon hainatuni, argues, perhaps, for the conjecture that the organ is an organ of sense, 

 but then it is exceedingly strange that such an organ should only be found within the 

 larvse. And it would be difficult to explain the meaning of the single or numerous long 

 threads as being sent forth from an organ of sense, whereas in relation with a gland their 

 function can easily be understood. 



The study of this same organ which I made last summer in the laboratory of Prof. 

 Lacaze-Duthiers, at Roscoff, has also convinced me, that my original supposition as to the 

 function of these organs was erroneous. The fine threads, which I observed in the 

 interior of the mandible running towards the organ are threads of connective tissue ; 

 their function is, no doubt, to hold the organ in its place. The young of Nymphon 

 rohustum, Bell, and those of Nymphon hrevicaudatmn, Miers, are a great deal more 

 developed when creeping out of the egg than those of Nymphon hamatum, N. longicoxa, and 

 N. hrevicoUum. Most probably this spinneret of the larva does not occur in these species. 



Besides the larvse of the genus Nymphon, the only other genus of which I could 

 investigate the larvse was Ascorhynchus. About their development and metamorphosis 

 nothing as yet has been published. I can only give a drawing of the single larval 

 stage which I observed, and- which is furnished with three pairs of legs. The fig. 6 

 on Plate XX. shows that the larva in this stage corresponds with larvse of other genera, 

 as observed by Kroyer, Dohrn, and myself. Of the glands in the foot-jaw no trace 

 could be discovered ; but then the larvse are very small, and their condition is not very good. 



8. In studying the anatomy of the Pycnogonids of the Challenger Expedition, I met 

 with two different kinds of bodies of which I have not been able to ascertain whether they 

 really belong to the organisation of the Pycnogonids, or must be considered as parasites. 

 However, I feel much inclined to adojrt the latter opinion ; and although some doubt 

 remains, I wish to give a short description of what I have seen, which may, perhaps, 

 be of use for later investigators. 



In the first place I met with some curiously shaped forms in the interior of the body and 

 of the legs of two different species of Nymphon. I observed them in Nymp)hon longicoxa 

 and in Nymphon hrevicaudatmn, but only in some of the specimens which belonged to 



