38 



the females, e. g. where the antennulse of the females are well developed and 3-jointed, those 

 of the males are equally so, and where they are reduced in size or in number of joints, we 

 generally — though not always [Splicer, microcephala, Mysidion commune) — find a similar 

 reduction in the male. In Splicer, microcephala (pi. VIII) the antennulse of the female are 

 very short and 1-jointed, those of the male long and likewise without distinct articulation. 

 In Mysidion commune (pi. XI and pi. XII) those of the female are very short and 1-jointed, 

 those of the male short and 2-jointed. Their bristles are much the same as in the female, 

 and they have frequently a rather conspicuous olfactory seta. The greatest reduction is noticed 

 in Aspidoecia (pi. XII, fig, 3 k and fig. 3 1), the antennulse of which consists of a very short, 

 naked joint terminating in an olfactory seta which is several times longer than the antennula. 



The Antennae, are altogether so like those of the female that a special description of 

 them is superfluous; where they are wanting or reduced in the female, they are equally so 

 in the male. 



The Hostrum is very like that of the female, but seems now and then to be longer 

 and more slender; in Splicer, microcephala it is much longer than that of the female (pi. VIII). 

 In several species, e. g. in Splicer, modesta (pi. IX), the mouth-border is much broader, its 

 hairs at least are considerably longer in the male than in the female. 



The Maxillulce are always found and are constructed like those of the female. In 

 dissecting the head of a male of Splicer, frontalis I found that, in addition to the two long — 

 though unequally long — principal branches and the long additional branch, the maxillula 

 of this animal possesses a fourth shorter one (pi. VII, fig. 6 d), which proceeds within the 

 base of the anterior principal branch. As this supplementary branch is not likely to be 

 discovered without undertaking a dissection expressly for this purpose, I cannot tell whether 

 it is found in the female as well; without dissecting the rostrum I have looked for it in 

 vain in the female as well as in both sexes of other species of Sphceronella. Fig. 41 in 

 pi. III. will give a good idea of the rostrum with antennse and maxillulse in a male which 

 possesses all these organs in their typical form. 



The Maxillce are well developed in nearly all species and are in the main constructed 

 like those of the females; sometimes they are somewhat smaller, sometimes rather larger, in 

 Aspidoecia (pi. XII) much larger. Occasionally we find differences of detail in the two 

 sexes; in Splicer, capensis the basal joint of the male has at its distal end, where the inner 

 and the posterior side meet, a rather high, prominent plate, the margin of which runs out 

 into spiniform processes (pi. VI, fig. 1 c and fig. 1 d) ; this excrescence is wanting in the female. 

 In the male of Sphcer. insignis the posterior side of the basal joint is provided with a conside- 

 rable number of peculiar processes (pi. X, fig. 1 c) which the female lacks. In Splicer, margi- 

 nata (pi. XIII) whose female has rudimentary maxillae, these organs in the male have about 

 the same general shape and size as in kindred species, but all three joints are fused together. 



The Maxillipeds are well developed in all species and essentially like those of the 

 females, though in the male the basal joint is frequently provided with hairs, and also some- 



