104 Mr. W. Clark on the Animals of the Bullidae. 



think it has the latter function ; it is never flaccid, but always 

 distended : where is the source of the large mass of fluid ? Its 

 external coat appears a network of minute vessels, and I presume 

 they are the ducts which distil the secretion from the larger 

 veins. The " organe generateur " when not exserted lies doubled 

 up in the oesophageal cavity ; it is of trifid form, that is, finger, 

 spindle, and club-shape, which latter portion extends to and lies 

 on the gizzard ; there is no internal connection between it and 

 the testis. Of this I am sure, as in consequence of the shape and 

 position of the parts, that fact admits of being accurately ascer- 

 tained. It may therefore be considered as almost certain, that 

 the long, slender, open groove, which by the muscular contraction 

 of the sides can be closed so as to form a canal, extending from 

 the orifice of the verge to the entrance of the common cavity, 

 must be regarded as a continuation of the vas deferens of the 

 testis, which passing under the matrix, or through it — which of 

 the positions is doubtful — unites with the open canal that termi- 

 nates at, but does not pass into that organ, and thus the vivifying 

 influences are enabled to make the necessary contact. M. Cuvier's 

 figure of the branchial plume presents a vertical and partly hori- 

 zontal face. Having examined many specimens, it appears to me 

 to be a single regular crescent-shape plume of eighteen or twenty 

 short coarse strands, having the artery in the centre, lying in a 

 crypt transversely between the vulva and the anus, floating free, 

 except where under the mantle it is fixed to its roof and to the 

 back of the animal ; the heart is oval, white, and with the auricle 

 placed as usual in a pericardium, at the base of the branchiae. 

 With regard to the veins and arteries I have not attempted to 

 trace them ; the circulation is of course complete ; but if, as in 

 Aplysitty there are any particularities attached to it, I do not 

 think that they will easily be detected in so small an animal. 

 There is nothing particular in the muscular system ; it exhibits 

 the usual masses of transverse and longitudinal fibres, which 

 throw off" from the internal surfaces the necessary muscular fila- 

 ments. The Bulla hydatis may be considered as the type of the 

 general aspect of the anatomy of the family of the Bullida. 



The slight rectifications I have ventured to suggest, even if 

 established, in no way detract from the general accuracy of the 

 great anatomist I have alluded to ; if I am right in my sugges- 

 tions, it is entirely due to having at my disposal numerous living 

 specimens ; but M. Cuvier, I infer from his memoirs, had often 

 only one or two indifferent specimens from spirit. His merits 

 and labours exhibit a noble example of what may be accomplished 

 by assiduous application, combined with a mighty genius ; he is 

 the pilot and Columbus of modern malacology, and even his suc- 

 cessors have little more merit than as " imitatores;" for what we 



