40 PEOF. HUXLEY ON SOME POINTS IN THE 



ture in the one case, and by the funnel-shaped channels which 

 have been miscalled " hearts " in the other. 



The rudimentary renal organs of the Ascidian are developed 

 in the walls of the cavity in question ; and an aquiferous chamber 

 of smaller dimensions has the same relation to the kidney in 

 Lamellibranchiata — in Gasteropoda, Heteropoda, Pteropoda, and 

 dibranchiate Cephalopoda. But although such is likely enough to 

 be the case, we do not know at present that the aquiferous chambers 

 in any of the last named moUusks attain an extension similar to 

 that which obtains in Nautilus. 



On comparing the observations detailed above with the state- 

 ments of previous writers, I find that, in his well-known " Memoir 

 on the Pearly Nautilus" (1832), Professor Owen describes "on 

 each side, at the roots of the branchiae," "a small mamillary 

 eminence with a transverse slit which conducts from the branchial 

 cavity into the pericardium. There is, moreover, a foramen at 

 the lower part of the cavity (o, pi. 5) permitting the escape of a 

 small vessel ; and by the side of this vessel a free passage is con- 

 tinued between the gizzard and ovary into the membranous tube 

 or siphon that traverses the divisions of the shell, thus establish- 

 ing a communication between the interior of that tube and the 

 exterior of the animal." 



The foramen here described is easily seen ; but, as I have stated, 

 there are other modes of communication between the so-called 

 pericardium and the cavity with which the siphuncle communi- 

 cates, of a far more extensive nature. 



With respect to the pericardium itself. Professor Owen states, 

 " The peritoneum, after lining the cavity which contains the crop 

 and liver, and enveloping those viscera, forms two distinct pouches 

 at the bottom of the pallial sac, in one of which, the left, is con- 

 tained the gizzard, and in the other the ovary ; anterior to these, 

 and on the ventral aspect of the liver, is another distinct cavity, of 

 a square shape, which contains the heart and principal vessels, 

 with the glandular appendages connected therewith," This is 

 what the author terms the pericardium. 



As Van der Hoeven has pointed out, however, the gizzard lies to 

 the right and the ovary to the left. Moreover, the gizzard is 

 superior to the ovary, so as only to overlap it a little above ; and I 

 can find no evidence of the existence of such distinct pouches as 

 those described. 



Professor Owen states that the branchiae " arise by a common 

 peduncle from the inner surface of the mantle." My own obser- 



