30 



Before leaving the head I will mention some peculiar formations, which I am at a loss 

 to understand. In Sphcer. frontalis we notice at the middle of the frontal margin (pi. VIII, 

 fig. 1 d) a strange cup-shaped, rather large expansion in which I have been unable to find any 

 hole which might be the outlet from some gland. In Sphcer. modesta, on the ventral side of 

 the protruding frontal border, inside its margin we see a square of considerable size (pi. IX, 

 fig. 2d, x) with rounded corners, which seems to be pierced with rather numerous holes. 



The TrnnJc. The body — except the head — of course corresponds to thorax and 

 abdomen, but in the tliree genera treated here, the latter never appears as a separate part; 

 we must consider it as being represented by the genital area and its surroundings, which, 

 however, are not marked by distinct outlines. I beg to give notice that, as a separate 

 abdomen only appears in the genus Stenothocheres (s. below) and in no other genus of the 

 whole family, I shall — for practical reasons • — in mentioning and describing all the genera, 

 except Stenothocheres, always both here and in the systematic part use the word » trunk" for 

 the whole body, except the head. 



The shape of the trunk is mentioned above, for as the head, at least in adult spe- 

 cimens of most species, is very small, I can refer to my description of the body (p. 24 — 25). 

 The skin — except on the genital area — is very thin, often quite naked, sometimes covered 

 with hairs behind the head, being naked everywhere else, sometimes hairy all over. In several 

 species the trunk is more hairy during the early, not half-developed stages, than when the 

 animals have grown to their full size, so e. g. in Splicrr. danica, whose young ones are covered 

 all over with peculiar thin, flat hairs, whereas the older specimens are either quite naked or 

 have only a hairy pait behind the head. In Sphmr. Calliopii (pi. Ill, fig. 3 d and fig. 3 g) the 

 trunk has a rather close coat of very peculiar three-branched hairs growing out from tiny 

 knots , the middle hair being longer than the two others. In Sphcer. irregularis (pi. XIII, 

 fig. 5 c and fig. 5 d) somewhat similar two- and three-branched hairs are seen. 



In most species the trunk has two pairs of entirely uniform legs, but in a good 

 number of species (as in Sphcer. microcephala, and in all eight species of the Sphceronella living 

 on Cumacea and Isopoda) legs are entirely wanting. The legs are placed on the ventral 

 side, now at some distance within the outline, now at the lateral margin, and as a rule there 

 is no considerable difference in the distances between the first pair and the head, between 

 the first and second pairs and between the second pair and the leg-like caudal stylets. In 

 J3bmoeosce& the legs, though small, are comparatively conspicuous, each apparently consisting 

 of a diminutive, short and rather thick basal part, from which proceeds a much longer, very 

 narrow, conical, almost setiforni branch and a pair of very short bristles or a short tap as 

 an indication of a second branch. In Sphceronella and Choniostoma the legs are nearly always 

 exceedingly small; in recently hatched or young specimens they are as a rule easy to find, 

 but as they do not grow, they are often very difficult to point out in adult animals. Each 

 leg consists of a small cylindrical joint ending in two short setse. In Sphcer. longipes (pi. VII, 

 fig. 2 a and fig. 2e) only, the legs are somewhat larger, particularly because one of the sette 



