Mr. E. A. Smith on the Genus Paludina. 221 
we invariably meet with intermediate sizes, which with cer- 
tavnty can neither be considered small females nor yet large 
males. ‘Then, again, as in other classes of the animal king- 
dom, individuals of the same species of both sexes vary much 
in their dimensions ; consequently that which we might deem 
an ordinary-sized female would possibly prove to be an 
overgrown male were the inhabitant known, and vice versd. 
Mr. Wood-Mason says, in reference to the difference in the 
size of the shell, “ It is far from probable that any other Gas- 
teropodous genera will be found to present similar sexual 
differences.” But this feature has already been noticed in 
the whelk tribe (Buccinwm) ; for Messrs. H. and A. Adams 
(Genera Recent Moll. vol. i. p. 108) observe, “ The shells 
of the males are generally smaller than those of the females,” 
aresult due probably to the same cause as in Paludina, namely 
the greater space requisite to contain a distended ovarium. 
In the quotation from Professor Owen’s work (‘ Lectures on 
the Comparative Anatomy and Physiology of the Invertebrate 
Animals,’ 1855, p. 564) there occurs an important mistake. 
Mr. Wood-Mason observes that in Paludina vivipara the 
penis “‘ is closely connected with the right tentacle” (Owen). 
From this it might seem to some that the great anatomist was 
somewhat indefinite in his demonstration. However, if the 
line had been correctly quoted, and the words ‘‘wnited to” 
substituted for connected with, the sense and clearness of the 
description become apparent. Moreover, can it for a moment 
be conjectured that the writings of Lister and Cuvier upon 
this subject were unknown to the distinguished author. 
Mr. Wood-Mason goes on to say, “ but in the Indian species 
the penis is altogether aborted, and its function has been 
transferred to the contiguous right tentacle, which has conse- 
quently become converted into a hooked copulatory organ.” 
From this it would appear that he imagines that in P. v7- 
vipara the penis arises from a spot somewhere near the right 
tentacle, whereas it is contained within it, as in his Indian 
species, and although contained by it, does not, I conjecture, 
transfer its function at the same time, the tentacle bemg but 
as a sheath to the penis, which, at the time of copulation, 
protrudes through the end of it. 
Beyond the fact of the tentacle in question being curved or 
hooked in P. crassa and P. bengalensis, we gain little further 
knowledge of this genus from Mr. Wood-Mason’s paper; and 
it is advisable that inquiry should be made concerning what has 
already been done upon any subject before trespassing upon 
the valuable space of such a journal as the ‘Annals and 
Magazine of Natural History.’ 
