REPORT ON THE SCHIZOPOPA. 167 



arising from the bottom of the incurvation being very small, whereas the three 

 following on either side increase in size successively. Of the three outer spines, 

 occupying the lateral corners, the innermost is by far the largest, projecting consider- 

 ably beyond the others. 



The uropoda, wanting in the smaller specimen, were distinctly developed in the 

 other (fig. 17), though still rather small. 



Furcilia Stages (figs. 3-5, 18, 19). — There are several successive stages in the collec- 

 tion, of which 1 have figured two, having a length respectively of 4'20 mm. and 5"00 mm. 

 They all are distinguished by an exceedingly slender form and a distinctly marked 

 median bend of the tail. 



The carapace has lost the hood-like expansion characteristic of the Calyptopis stages, 

 the frontal margin being deeply emarginate on either side, so as to allow of the eyes 

 projecting freely, and juts out in the middle as a narrow horizontal rostral projection, 

 which in the earlier stage (figs. 3, 4) is truncate at the tip. The inferior margins 

 of the carapace are, moreover, armed posteriorly to the middle with a strong denticle. 



The eyes exhibit nearly the same appearance as in the Calyptopis stages, being, 

 however, a trifle more tumid iu the middle, and also distinctly pedunculated and 

 mobile. In the latter of the two stages figured here a densely crowded fascicle of visual 

 elements (crystalline cones), enveloped at the base by a dark pigment, has appeared 

 within the extremity of the eye (fig. 8), corresponding, as to number, to the seven 

 lenticular corpuscles mentioned above as occupying the tip of the eye. As will appear 

 from the following development, this is quite a provisional visual apparatus, the true 

 cornea not being developed till a much later period. 



In the younger of the two specimens figured here (figs. 3, 4) no trace either of the 

 legs or of the pleopods has yet appeared, the limbs being precisely the same as in the 

 Calyptopis stages. On the other hand, in the somewhat older specimen represented 

 (fig. 5), the budding anterior legs, as also the first trace of the gills, may be distinctly seen 

 behind the maxillipeds. Moreover, on each of the three anterior caudal segments a pair 

 of pleopoda have appeared, but very small, immobile, and without bristles. 



The telson (figs. 18, 19) has become rather narrow, scarcely at all expanded at the 

 extremity, which is at first rounded ofi" (fig. 18), without any trace of the original median 

 incurvation. The seven median spines form a continuous row occupying the most 

 prominent part of the extremity, which becomes gradually more prominent (fig. 19), and 

 at length juts forth as a median process on either side of which the large innermost one 

 of the outer spines projects. 



Cyrtopia Stage (figs. G, 9, 20, 21).— In this stage the animal has a length of 6| to 7 

 mm., and already exhibits certain characters indicating its parentage. Thus, the carapace 

 presents above, at some distance posterior to the rostral projection, a small knob-like 

 prominence as a trace of the peculiar flattened spine characteristic of the adult animal. 



