156 THE VOYAGE OF H.M.S. CHALLENGEE. 



examination, and tluis T liavc lieen enabled to trace the development of this species 

 through all its numerous successive stages comprised between the second Calji^topis 

 stage and the adult form. Of still earlier stages, on the other hand, no examples were 

 found in the collection, and hence I have deemed it advisal)le to treat of the develop- 

 ment of the present form next after NyctijyJianes australis, of which the earliest larval 

 stages found have been described above. 



"With a view to show the progressive development of the several liml)s, I have 

 carefully dissected specimens of all the stages here described ; and in PL XXX. series 

 of figures of the same limbs, in different stages of development, have been given. I 

 first propose to describe in general the more marked stages, and then shall pass 

 on to a detailed investigation of the chief modifications the limbs undergo during 

 development. 



A. General Description of the successive Larval Stages (PI. XXIX.). 



Second Calyptopis Stage (figs. 1, 2). — From the corresponding stage of Nyctiphanes 

 australis, this is easily recognised Ijy the spine-like projection formed by the carapace 

 posteriorly, as also by the anterior margin of the hood-like frontal part being finely 

 denticulate. Moreover, the terminal segment of the tail (telson) would appear to 

 be somewhat more produced and slightly deviating in its armature. In all other 

 respects the larva closely resembles the corresponding stage of Nyctiphanes. Length 

 of body 1^ mm. 



Last Calyptopis Stage (fig. 3). — This is precisely the same stage figured by Professor 

 Claus in his treatise referred to above. It corresjaonds to the last described larval stage 

 of Nyctiphanes, from which, however, it differs, in addition to the characters distinguish- 

 ing the former stage, by the presence, on either side, of a well-marked lateral denticle 

 projecting from the lower margin of the carapace posterior to the middle. Length 

 of body 2-20 mm. 



First Ftircilia Stage (figs. 4, 5). — The most prominent feature distinguishing this 

 stage from the two preceding ones, is the pronounced development of the compound 

 eyes, which have now become mobile and freely projecting beyond the edges of the 

 carapace, instead of, as in the Caly^^topis stages, being immolnle and hidden beneath 

 the hood-like frontal part of the carapace. In accordance therewith, the anterior part 

 of the carapace is somewhat altered, a distinct emargination having apj)eared on either 

 side, limited beneath by an acute angle (the antero-lateral corners), and marking ofi" in 

 the middle a broad frontal plate arching over the basal part of the eye-pedicles and the 

 antennular peduncles (see fig. 5). This plate has a somewhat cordiform shape, being 

 slightly produced in the middle, and having the lateral edges evenly curved and finely 

 denticulate. 



