10 , Mindeskrift for J. Steenstrup, XVI. 



which is obscured by the close opposition of its members; this apparently unpaired 

 muscle runs in the middle line obliquely from the ventral base of the caudal appendix, 

 over the receptaculum seminis, between the distal ends of the oviducts to the front 

 margin of the genital segment, where it is inserted at the posterior ends of the longitudinal 

 ventral muscles. Very feeble muscular strands, traversing the posterior part of the 

 genital segment, and inserted at the dorsal base of the appendix, seem to aet 

 antagonistically to the grcat oblique muscle. On the ventral side of the genital 

 segment the fanshaped dilatator for the vulva, mentioned above, originates laterally in 

 the body-wall and is inserted in the thickened outer lip of the vaginal slit. 



All the appendages are provided with intrinsic muscles; those of the antennæ 

 and thoracic limbs are feeble, those of the antennules stronger, and those of the 

 maxillæ very strong. 



The whole muscular equipment apparently allows a certain amount of mobility 

 which hardly would be expected in an animal like this, confmed inside a tightly 

 fitting capsule. 



The adult male (PI, I, Fig. 1, 4, 11, 12) is considerably smaller than the ripe 

 female, reaching at most a length of 2 mm. At first sight it seems very unlike the 

 female, slender, almost cylindrical, curved, and resembling an insect-maggot, but 

 closer inspection reveals fundamentally the same structure. The head takes up 

 between the third and fourth part of the total length; a carapace is distinctly marked 

 off, and trace of a rost rum may be seen between the antennules; the four thoracic 

 segments are very evident, the posterior one somewhat shorter than the three anterior; 

 taken together they make up the greater part, more than half the total length. The 

 body tapers evenly towards the abdomen. The latter is short, unsegmented (but also 

 here representing three segments, as shown by the larva). The part representing the 

 genital segment also in the male is by far the greatest and send s out on each side a 

 large outgrowth (1), conical, firmly chitinized and directed backwards, reaching (almost) 

 as far as the end of the tail; it corresponds to the clumsy lateral outgrowth in the ripe 

 females, and resembles — to a certain degree — that of the youngest unripe females, 

 as upon the whole the general likeness with the latter is more conspicuous. Ventrally 

 the genital segment carries genital openings (Fig. 11, go); they form large crescent- 

 shaped slits, arched over by the lateral opercular lips into which a special levator 

 muscle (Fig. 4 dil) is inserted. Towards the medial margin of the opercle short rows 

 of small hairs are found, at the posterior corner generally a larger spine or bristle 

 (largest in young individuals). The posterior end of the tail (ap), corresponding to 

 the "appendix" of the female, and representing two segments, forms a short narrow 

 part, terminating in two bifurcated claws; the outer one of each of these is generally 

 somewhat larger, the inner one provided ventrally with small hairs or bristles. In 



