Dr. H. Lacaze-Duthiers on the Float of the lanthine. 279 
but his investigation had been made upon individuals preserved 
in spirits. He adds, “The organ has no direct communication 
with the interior of the body; it is a mere appendage of the 
integuments. And it does not appear that the animal can at 
pleasure empty or fill it with air; it can only compress it by 
drawing it into the shell, or leave it to its natural elasticity by 
allowing it to escape”’*. 
I have been able to examine animals in the expanded and 
contracted states—even strongly contracted, such as those which 
the sea had rolled upon the beach; and it is impossible to admit 
that the float enters entirely within the shell; it follows the 
Tanthina as it withdraws, but it is not introduced into the shell 
as a part of the organism. 
All differences of opinion will be easihy explamed when we 
have shown what is the real origin of this curious object. It will 
be seen how erroneous was the opinion of Bosct (already justly 
criticised by Cuvier) when he said that? the animal absorbs the 
air from its vesicles and inflates them at pleasure. Cuvier adds, 
“This assertion of Bose is only a supposition, and not a fact 
ascertained by direct experiments.” Even the very presence of 
the organ did not appear to the celebrated naturalist to be ab- 
solutely necessary ; for he says distinctly, “ All individuals do 
not possess this organ: I have three which do not show the 
least trace of it.” 
Bory Saint-Vincent had no doubt observed the living Lanthina 
in his voyages ; and he says, “I have not observed that the ani- 
mal had the faculty of emptying or filling it at pleasure and 
with promptitude”{. The same observer adds that he has seen 
Tanthine ‘‘in which the organ had been crushed, or reduced 
one-fourth, without their appearing to have suffered.” And 
Cuvier, who cites this opinion, remarks that “its nature is in 
fact such that Lanthine deprived of it by violence would proba- 
bly experience no other inconvenience than that resulting from 
the difficulty of rising to the surface of the water.” 
All this is in accordance with its anatomical nature—that is 
to say, the independence of the tissue and of the float, but not 
with its origin and nature. Thus, when Cuvier adds, “ But I 
have reason to believe that there are some which are naturally 
deprived of it,” he makes a supposition, and his opinion ex- 
presses doubt when he seeks to give its explanation. Thus he 
invokes age and the season of the year to explain its absence, 
his reason being that he was unable to “ perceive any cicatrix 
* Cuvier, “ Mémoires pour servir a l’ Histoire et & l’ Anatomie des Mol- 
lusques”’ (Mém. sur la Ianthine et la Phasianelle, p. 4). 
+ Coquilles, tome iv. p. 74. 
{ Voyages, tome i. p. 241. 
