39 



times with processes, whereas in the female there are no processes and fewer or no hairs 

 etc. In Mysidion commune the male possesses on the outer side of the basal joint a knot- 

 like excrescence and a process of very considerable size (pi. XI, fig. 3 g and fig. 3 h), and 

 its second joint has a conspicuous process, all of which are wanting in the female. In Aspi- 

 cloecia (pi. XII) the female lacks maxillipeds; in the male, though somewhat smaller than 

 usual, they are well developed: the basal joint is much as in Stenothocheres, but the second 

 joint, which as in several other forms consists of two completely fused joints, is exceedingly 

 short, somewhat shorter than the terminal joint. 



Trunk-legs and caudal stylets. The occurrence of these organs is mentioned above 

 on p. 36. In Homoeoscelis (pi. II and pi. XIII) there is but a slight difference between 

 the two similarly shaped pairs of trunk-legs and the caudal stylets, and as both are like 

 those of the female, they do not require further mention; we shall only add that they are 

 sometimes rather larger than, sometimes of the same size as those in the other sex. In Stenotho- 

 cheres (pi. I) the trunk-legs are very similar to those of the female and of almost equal size, 

 however, as the trunk of the female is large, that of the male small, of course the legs of the 

 latter are much more conspicuous and appear larger. In the male the basal part of the legs 

 stands more out from the body, and the longer robust terminal spine on the outer branch is 

 longer than in the female; the other differences are insignificant. Thus, in Stenothocheres 

 Sarsii the spine on the inner branch of the second pair of legs is curved like a hook, in 

 Stcn. egregius it is less curved, and in the illustrated specimen the right and the left spine 

 curve differently. Behind and above the basis of the second pair of legs both species show 

 two considerable spines which are situated close together on a small projection; I should 

 think they might possibly be considered as rudiments of a third pair of legs, but I do not 

 presume to have any definite opinion about the matter. The abdomen is small, with short, 

 distinct, rather broad stylets, not set off by an articulation, and each provided with four 

 spines, of which the two innermost are the longest and thickest. 



In Sphceronella, as a rule, there is a great difference between the two pairs of trunk- 

 legs and between each of these and the caudal stylets. The shape and size of the trunk- 

 legs vary much according to the species, and the appearance of the legs as well as of the 

 stylets presents very great variation on account of the very different length of their terminal 

 setae. In this genus the first pair of legs usually originates outside and behind the basis of 

 the maxillipeds, nearly in the middle between the lateral margins and the median line of the 

 trunk, at the bottom of a pretty broad transverse depression. Each leg consists of a basal 

 part, a peduncle, differing much in length and breadth (sometimes, as in Splicer, intermedia 

 (pi. V, fig. 3 f and fig. 3 g), this part in exceedingly large) , and of two branches, one of 

 which is generally longer than the other, sometimes the one is wanting altogether. As a rule, 

 none of the blanches are articulated on the peduncle, and frequently one or both of them 

 terminate in setae, one of which is longer than the others, the one on the outer branch 

 often exceedingly long, occasionally half as long as the whole animal. The second pair of 



