104 THE VOYAGE OF H.M.S8. CHALLENGER. 
When comparing the number of these cavities in the fourth joint of the leg with that 
of the same organs in a transverse section of the body,—for example, between two lateral 
processes, where the circumference of the body is in some species nearly the same as that 
of the fourth joint of the leg,—I observed almost the same number of cavities. This 
was the case at least in Nymphon hamatum and in N. brachyrhynchus; whereas in 
the other species more or less considerable differences were observed, the number of these 
cavities in some species being greater in the legs; in others, on the contrary, round the 
body. 
With regard to the hairs and spines on the surface of the body, I have already pointed 
out above that, as a rule, species occurring at great depths are rather smooth, whereas 
those from shallow water are furnished with numerous hairs and spines. Thus Vymphon 
longicoxa and N. hamatum have the surface almost quite destitute of spines; Nymphon 
brevicaudatum and N. hirtipes occurring at moderate depths, the former not exceeding 
120 fathoms, the latter never reaching 300 fathoms, and generally found in considerably 
shallower water are the most hairy species of the genus. On the contrary, Nymphon 
brachyrhynchus, occurring at depths not exceeding 120 fathoms, is almost as smooth 
as Nymphon hamatum. 
The species of Colossendezs, and especially the three more accurately studied by me, 
show almost a perfectly smooth surface. The sensory setee are wanting also in these species ; 
and the few spines which are present are very short and conical (Pl. XVI. fig. 13). Of 
these three species, two are true deep-sea inhabitants; but the third (Colossendeis 
proboscidea, Sab. (sp.), as a rule, is found at a depth not exceeding 200 fathoms. Of the 
species of Ascorhynchus, the smooth A. glaber is found at a depth of 1375 fathoms ; 
but the surface of Ascorhynchus orthorhynchus is also not very hairy, yet this species 
occurs at a depth of only 130 fathoms. 
The shallow water genera Achelia and Ammothea are extremely hairy, whereas in 
the genus Phoxichilidiwm some of the deep-sea species (P. piloswm and P. mollissimum) 
show a particularly hairy surface. Both the spines and the sete are in these species of 
a very remarkable length. Finally, Pallene australiensis, occurring at a depth of 38 to 
120 fathoms, shows again the smooth surface of a true deep-sea species. 
The form of these spines is also very different, but I think it is not necessary to describe 
them. In some species the spines are not smooth, but serrated ; as, e.g., in the case of 
Nymphon brevicaudatum, Miers, and Pallene australiensis, Hoek (Pl. XI. figs. 6, 7) ; and as 
spines having a very curious shape I have pointed out already those of the sixth joint of the 
ovigerous leg of Nymphon longicoxa. No doubt, these must be of great use to the animal in 
holding the egg-masses, and perhaps also in furnishing a good point for the young ones to 
cling to. Particularly interesting are also the so-called denticulate spines in the four last 
joints of the ovigerous legs of most species. I may refer to the descriptive part of this report 
for an account of their extremely different forms, their numbers, and their arrangement. 
