166 THE VOYAGE OF H.M.S. CHALLENGER. 



Cahjptopis Stages (figs. 1, 2, 7, 13-17). — I have only had the opportunity of examining 

 two not very well-preserved specimens in these early larval stages, and have figured both. 

 They were found to represent two successive stages, ajjparently corresponding to the two 

 last Calyptopis stages, as described above of Nyctiphanes and Eupliausia. The length 

 is respectively 2 J- and 3| mm. 



The form of the body in both specimens (figs. 1, 2) is very slender, especially the 

 tail. The carapace is rather large, with evenly arched edges, and forms in front a hood- 

 like expansion, covering the eyes and basal ^Vixta of the antennula?. The tail is 

 distinctly segmented, but in the smaller specimen (fig. 1) the last segment has not yet 

 been defined from the telson, whereas in the other (fig. 2) all the segments are 

 distinct. 



The eyes (fig. 7) exhibit a very peculiar form, being oblong-ovate, with the 

 extremity tapering to an obtuse point, on which occur seven distinctly marked len- 

 ticular facets of the outer integument. Imbedded within each eye is a dense fascicle 

 of delicate fibres extending well-nigh in the longitudinal axis, and apparently repre- 

 senting the luminous organ. 



The antennulse and antennge exhibit much the same structure as in the corre- 

 sponding stages of Nyctiphanes, the former organs consisting in both specimens of a 

 triarticulate peduncle and two very small uniarticulate flagella ; moreover, in the larger 

 one, the strong spine arising fi-om the basal joint exteriorly has been developed, whereas 

 in the other it is stiU wantino-. 



O 



The four pairs of ventral (oral) apjDendages (figs. 13-16) also present considerable 

 resemblance to those in the Calyptopis stages of Nyctiphanes and Euphausia, though 

 differing in the following particulars : — 



The projection jutting out from the mandible (fig. 13) at the base of the masti- 

 catory part is remarkably large and spiniform, tapering to a very acute point. The 

 palp, or terminal part, of the first pair of maxillae (fig. 14) consists of a single joint 

 bearing three bristles only. That of the second pair of maxillte (fig. 15) is exceedingly 

 small. On the other hand, the exopodite of the maxillipeds (fig. 16) is relatively 

 larger than in the corresponding stages of Nyctiphanes and Euphausia, projecting con- 

 siderably beyond the endopodite, and furnished with five strong ciliate setae, exclusive 

 of a much shorter seta affixed to its base. 



The telson (fig. 17) exhibits the usual spathulate form, being conspicuously 

 expanded towards the apex, which is slightly incurved in the middle, with the lateral 

 corners evenly rounded off". It is armed with the same number of spines as in the 

 larvae of Euphausia, viz., two lateral and thirteen terminal, but the spines are slightly 

 different as regards arrangement and relative size. Thus the lateral spines are 

 affixed somewhat anteriorly to the middle, not posterior to it, as in the larvae of 

 Euphausia. Moreover, the terminal spines are rather unequal in size, the median. 



