REPORT ON THE SC'HIZUPODA. 109 



The telson assumes, even iu the first of the post-larval stages, the form cluiracteristic 

 of the adult animal, the apex (fig. 22) l^eiug produced into an acuminate point, armed on 

 either side with three small denticles — the original terminal spines. Moreover, the outer 

 spine, occurring in the last Cyrtopia stage next to the subapical spines, has entirely 

 disappeared. 



Development of Nematoscelis rostrata, G. 0. Sars (PI. XXXI. figs. 23-29). 



The earlier larval stages of this form would not seem to exhibit any marked 

 peculiarities, and hence I shall only describe three of the later stages, in which the 

 characters of the genus are first discerned. Two of these are Furcilia stages, the third 

 a Cyrtopia stage. 



Furcilia Stages (figs. 23, 24, 26-28).— The form of the body in these stages, which 

 measure respectively 3^ mm. and 4 mm. in length, is far from being so slender as in the 

 corresponding stages of Thysanopoda tricuspjidata, resembling in this respect more closely 

 the Furcilia stages of Euphausia. 



The carapace has on either side a very strong lateral denticle, projecting from the 

 inferior margin posteriorly to the middle, and is als(j distinguished by a conspicuous 

 rounded crest, rising from about the middle of the dorsal face. The rostral projection is 

 very large, horizontal and sharply pointed, though broad and flattened at the base, more 

 especially in the earlier stage. 



Of legs, two pairs have made their appearance, being, however, in the earlier of the 

 two stages (figs. 23, 26) still very imperfect as to structure, non-articulate, and without 

 bristles. But even in this rudimentary state the peculiar modification of the first pair, 

 so characteristic of the genus, is distinctly recalled, the corresponding buds (fig. 26) being 

 remarkably massive, and exhibiting a most conspicuous S-shaped flexure. In the later 

 stage (fig. 24) both of the two anterior pairs of legs have become articulated, and the 

 first pair now very clearly present the peculiar structure characteristic of the genus 

 Nematoscelis, though they are as yet far from having attained their fuU length. In this 

 stage also some of the gills are seen budding forth behind these legs. 



Of the pleopoda, four pairs only have been formed in the earlier of the two stages 

 (fig. 23), and of these the first pair only are difi"ereutiated into a basal part and terminal 

 plates, whereas the other three still represent merely simple bud-like processes. In the 

 later stage (fig. 24), on the other hand, all the pleopoda have appeared, and only the 

 last pair retain their original bud-like character, whereas the other pairs are fuUy 

 developed and adapted for swimming. 



The telson iu the earlier stage (fig. 27) is still rather broad, and slightly expanded at 

 the apex, with a pair of lateral spines about the middle of its length. The number of 

 terminal spines is that usually met with, viz., thirteen, seven of which form a continuous 



(ZOOL. CHALL. EXP. PART XXXVII. — 1885.) Oo 22 



