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



insertion of the antenuse, on cither side of the free edge of the anterior lip, separated 

 as yet in the middle by a rather broad interstice. They are comparatively small, 

 elliptical in form, and, on the outer side, drawn out to a conical point, the rudiment 

 of the powerful biramous mandibular legs occurring in the Nauplius stage. 



The three succeeding pairs lie in close contact with each other, forming rather broad 

 transverse intumescences, which, at the inner corner, jut forth as rounded, somewhat 

 posteriorly pointing lobes, double on the last pair (the maxillipeds). 



The part of the body posterior to the above described parts, constituting the rudi- 

 ment of the tail, is cpiite smooth, and somewhat flattened at the extremity, which is 

 broadly truncate, with a very faint emargination in the middle. On either side of the 

 emargination three very short spines are seen to arise from the edge. 



First Calyptoins Stage (figs. 4-19). — The body has in this stage a length of about 

 1 mm., and exhibits (see figs. 4, 5) a more distinct limit between an anterior and a 

 posterior division, the latter being, however, as yet much shorter than the former. 



The carapace is now more fully developed, with the free portion broader, manthng 

 over, as it were, the bases of the limbs, and forming anteriorly a hood-like " expansion, 

 that covers from above the anterior extremity of the body. The free edges are c[uite 

 smooth and evenly curved, without teeth or projections, forming, however, a slight 

 incurvation at the sides of the buccal area. 



The posterior di\'ision of the body lacks as yet every trace of segmentation, 

 constituting merely a simple, cylindrical projection, generally bent at a more or less 

 distinct angle. It is, however, rather mobile, and admits, by the aid of a well-defined 

 assemblage of muscles adjoining it on the upper face, of l)eing stretched in nearly the 

 same axis as the anterior division. At the extremity it is somewhat flattened and 

 abruptly truncate, and has the terminal edge (see fig. 19) armed with a row of twelve 

 strong ciliated spines, the six median about ecpial, the outer three on either side rapidly 

 increasing in length to the innermost, which is very large and projected far beyond the 

 rest. Besides the above-mentioned terminal spines a pair are seen arising from the 

 ventral face at some distance from the extremity, each of the spines originating a little 

 within the lateral edge. 



Immediately in front of the posterior division of the body may be observed a faint 

 and close wrinkling of the integument as a first indication of the segmentation of the 

 trunk (see fig. 6). 



The ocellus is distinctly perceptible, placed in the middle line at some distance from 

 the anterior margin of the carapace (see fig. G). When highly magnified (fig. 7) it is 

 found to contain two small refracting bodies protruding from the pigment anteriorly. 



On either side of the ocellus, and somewhat dorsally, occur beneath the hood-like 

 expansion of the carapace (see figs. 4, 5) two large cellular bodies, of a somewhat 

 compressed, semicircular shape, but as yet, however, comparatively indistinctly defined. 



