280 BULLION. 



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 

 terminates 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 horizontal face. Having examined many specimens, 

 it appears to me to be a single regular crescent-shaped 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 peri- 

 cardium, at the base of the branchise. With regard to the 

 veins and arteries I have not attempted to trace them ; the 

 circulation is of course complete ; but if, as in Aplysia, there 

 are any peculiarities attached to it, I do not think that they 

 will easily be detected in so small an animal. There is no- 

 thing 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 filaments. 

 The Bulla hydatis may be considered as the type of the general 

 aspect of the anatomy of the family of the Bullidee. 



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 

 suggestions, it is entirely due to having at my disposal nume- 

 rous 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, com- 

 bined with a mighty genius ; he is the pilot and Columbus 

 of modern malacology, and his successors have little more 

 merit than as " imitatores ;" for what we know he has taught 

 us, and those who have gone beyond him in the useful 



