THE OSTKACODA. 257 



CYPRIDINID^. 



Ctpridina castanea, Brady. 

 (Plate 26. figs. 279-281.) 



Two females, apiiarently of Stages I. and II., respectively about 0-0 and 4-0 mm. in 

 length, occurred in haul 32 m. The larger specimen carried ova free between the 

 shells posteriorly. The smaller was pale in coloui% except for the eyes, and for the 

 stomach wiiich had already the " chestnut " tint of the adult. 



Besides these, two larvte of 1'8 mm. and one of 1-9 mm. were taken. Dr. Miiiler 

 figures (xxsiv. 10) a larva of this description, but does not give its length. As he points 

 out, the shells are more circular and less elliptical at this early stage. 



The complicated arrangement of bristles and selvage (Saum) at the rostrum, which 

 he figures (xxxiv. 12) for the adult, is not quite identical with that of these larvae 

 (fig. 281) ; the selvage is traceable from above the rostrum along the ventral border as far, 

 at least, as the most prominent point of the posterior border, but is very narrow on the 

 ventral and posterior borders. 



The younger stage is proba1)ly identical with Vavra's Cypridina obesa. 



GiGANTOCTPRIS PELLUCIDA, MiiUcr. 



(Plate 26. fig. 282.) 



Two sjiccimens, the one perfect (and, if I remember riglit, alive), were obtained from 

 great depths. By size they belonged to Miiller's species pellucida : the perfect specimen 

 measured about 13 mm. ; in the other the shells were much crumpled and torn, but 

 they seemed to be of about the same length. I regard it, howevei*, as possible that 

 pelhickla is the penultimate stage of agassizii. 



The 13 mm. specimen (which was not dissected) coiitaiaed about 23 embryos between 

 the shells posteriorly : one of these Avas extracted and is represented in fig. 282 ; it was 

 still encased in a shell-membrane, and showed five pairs of appendages ; the shell-edges 

 had already begun to grow downw^ards. 



This and Cypridina castanea were the only cases noticed, in tiie whole collection, 

 of ova or embryos being carried by the mother after extrusion. 



III. DEVELOPMENTAL PART. 



The general method of handling the question of the successive moults — (1) by plotting 

 the numbers observed at each length and noting the range of the curves thus formed ; 

 (2) by testing these with a growth-factor found empirically — has been sufficiently 

 explained in the Introduction (pp. 224-226). The supposed law of growth by api)roxi- 

 niately similar increments at successive moults, here styled Brooks's law% requires to be 

 re-tested on larger Crustacea, where a hundredth of a millimetre will be a negligilile 



