328 Mr. W. Clark on the Animal of Dentalium Tarentinum. 
duction, and I think from various considerations that this ani- 
mal is an hermaphrodite, but without congression. Under the 
microscope, in the midst of the general mass, several small egg- 
shaped globules, having at one of the axes a minute, apparently 
tubular filament filled with a glary fluid, may be seen in some 
individuals, but not in all, as I have sometimes searched m vain 
for them ; these may be the virile fecundating organs, which are 
perhaps only apparent at certain stages of gestation. 
I have extended these observations to an unusual and almost 
inconvenient length: the curious and anomalous structure of 
this molluscum, and the multitude of interesting characters at- 
tached to it, exhibit such modifications of the organs of the ty- 
pical Gasteropoda as appear to give it a claim to be considered 
as the point of transition from the bivalve mollusca to the great 
change in figure and faculties which nature has produced in the 
superior developments of the Gasteropoda ; and perhaps from a 
review of this account of these organs, malacologists may be in- 
duced to think that it will appropriately form one of the first, if 
not the first link, in the chain of the Gasteropode. The symme- 
trical subventral position of the branchiz, the posterior flow of 
water to them, and the resemblance of the foot to that of some 
of the bivalves, combined with the similar character of its action, 
appear in a striking manner to show its connection with the Con- 
chiferze ; whilst by its cesophageal cerebral ganghons and com- 
pleteness of the circulation, it has established its claims as a 
Gasteropod. There are also traces of alliance with some of the 
inferior classes: the red blood and vermiform configuration of 
the posterior part of the animal show some of the characters of 
the Annelides ; but though we acknowledge these sources of its 
origin, we cannot fail to see how clearly the animal of Dentalium 
displays at various points the progress of advancement, and the 
ameliorations nature has so beneficently effected in its animality. 
I have only seen one live specimen of the Dentalium entalis : 
the organs have the same characters as those of the present spe- 
cies, but it is very distinct ; the colour is snow-white, and on com- 
parison of two shells of the same size, the Dentalium entalis will 
be found much more slender ; the branchiz are also of a paler 
green, more scanty, thin and delicate. 
I had written thus far when I received from Paris M. Deshayes’s 
memoir on the Dentalia, which I had. not seen for twenty years, 
and its contents had nearly passed from my memory ; on looking 
it over I find that the differences between that gentleman and 
myself are more important than I was aware of, but I am not 
inclined to abandon my own views. I am also elad to find that 
T am enabled to fill up many gaps as regards the functions and 
habitudes of these animals. 
This gentleman, in stating the anus in Dentalium to be pos- 
