EEPOET OlSr THE SCHIZOPODA. 27 



bent towards the ventral face, where it is freely suspended, meeting the corresponding 

 branch on the opposite side in the median line (see fig. 16), whereas the remaining three 

 branches occur on the exterior side of the legs and are completely covered by the 

 marginal portion of the carapace. Every gill-branch, too, consists of a median stem, 

 sending oil in comparatively regular sequence secondary branches from each side, 

 whereby the whole branch acquires a bipinnate appearance. The secondary branches or 

 pinnula3 are, furthermore, divided into a vast number of small lobes (see fig. 13) arranged 

 with less regularity, and even these lobes may occasionally be found, — especially on the 

 inner part of the gill-branch, — to be subdivided into smaller lobules. The final 

 ramifications of the gills are always of a simple cylindrical, or rather vesicular, form, 

 never, as in LopJiog aster, foliaceous. Eegarding the insertion of the gills, they would 

 seem to originate at the articulation between the bases of the legs and the pleuron of the 

 corresponding segment, and hence may properly be designated " arthrobranchise," although, 

 on dissection, they remain as a general rule in connexion with the legs. 



In the fully developed females, as with Lophogaster, seven pairs of large foliaceous 

 lamette, fringed at the edges with bristles, spring from the bases of all the legs, and, 

 folding one over the other in the median line, form a capacious marsupial pouch, pro- 

 jecting from beneath the trunk (see PI. 11. fig. 1 ; PI. V. fig. 1 ; PI. VI. fig. 6). 



In the males, on the other hand, may be observed, at the base of the last pair of legs 

 posteriorly (see PI. VIII. fig. 14, p, and fig. 15) and on each side, a small tuberculiform 

 prominence, representing the outer sexual appendage, and having at its extremity the 

 fissure-like opening for the eff"erent duct of the testes. 



The caudal limbs (PI. VIII. fig. 18) in both sexes are developed in the same manner 

 as powerful natatory organs, consisting of a somewhat applanated and strongly muscular 

 basal part, and two very elongate and slender terminal branches, the outer part of which 

 is subdivided into a great number of small articulations furnished with strong natatory 

 set£e. They all exhibit a perfectly uniform structure, none of them in the males being 

 distinguished by the slightest peculiarity, as is the case in the Euphausiidse and Mysidse. 



The telson (see PI. II. fig. 7; PL III. fig. 6; PL IV. fig. 7, &c.) is exceedingly large, 

 and has the upper face somewhat channelled along the middle, exhibiting on each side an 

 obtuse longitudinal keel. It is slightly constricted near the base, and tapers more or 

 less rapidly toward the ajDex, which juts out into two strongly curved spines, connected in 

 the middle by a serrate lamella, thus forming together an almost semilunar projection. 

 The lateral edges of the telson are densely spinulous throughout their distal portion, the 

 spinules being of somewhat unequal size, so that between two larger ones, as a rule, 

 occur a more or less considerable number of much smaller ones. At the base of the 

 telson, on the ventral face, is placed as usual the fissure-like anal opening. 



The uropoda (ibid.) are generally shorter than the telson, and consist of an 

 exceedingly short basal part and two terminal plates, which admit of being spread out on 



