Mr. C. Spence Bate on the Affinity of Prauiza loith Anceus. 171 



stage the rudiments of both sexes, — a cu'cumstance which, if 

 correct, would account for the gnathopoda being different in the 

 larva from the same organs in the adult female. I hope to be 

 enabled to set this point at rest before it is embodied in the 

 work I have in hand. 



With regard to Anceus, I have as yet no experience to lead 

 me to any conclusion. 



There is a mystery in the production of the ova of Prauiza that 

 would well repay the embryologist for studying. I have before 

 observed that they are occasionally taken transparent, white, 

 ash-grey, green, blue, and red-brown. These varieties of colour 

 appear to be dependent upon the progress made in the advance- 

 ment towards spawning, or in some way connected with the 

 development of the ova. 



"VMien the animal is blue, I have observed a double line of ova 

 traversing the length of the enlarged segment, as seen in fig. 4, 

 PI. VI., and figs. 7, 7", PI. VII. This I presume to be the ovary 

 or the oviduct previous to the escape of the ova into the incuba- 

 tory pouch, which they ultimately fill, to the apparent annihila- 

 tion of the other contents of this part of the animal. 



I have watched specimens in a glass, and perceived, after a few 

 days, that the blue mass, which at first appeared to fill and distend 

 the large segment of t\\e.pereion, gradually diminished, apparently 

 deteriorating. It recedes first from the margin. In so doing, 

 it displayed a series of layers, ])laced one before the other, lying 

 across the animal. There were indications also of these layers 

 being divided by cross-sections. It is from one so depauperized 

 that fig. 4 in each plate is taken. The ova ultimately fill the 

 pouch, first as seen at fig. 6. PI. VII., and ultimately as shown 

 in fig. 8, where the embryo has considerably advanced towards 

 completion. 



The blue appearance is now changed to a brown, — a circum- 

 stance that is due to the reddish pigment-cells which mark the 

 pereion of the young animal. 



The nervous system is similar to that of other Isopoda. The 

 ganglia of the three posterior fused segments are distinct, and an 

 intermediate branch is given off on each side from the nervous 

 cord, between each ganglion. One cord only appears to be given 

 off on each side of every ganglion except the one preceding the 

 last three of the pereion; this appears to give off three upon 

 each side. Those within the cephalon I could not distinctly 

 make out -, but, without being fused, two ganglia appeared to be 

 brought close together. Possibly the ganglion belonging to the 

 suppressed gnathopoda may be present. 



The animal is small, but the nervous system is readily detect- 

 able along the ventral surface of the undissected creatui-e. 



