7 
Il].—On the Vascular and Nervous Apparatus of the Larve of 
the Marine Crustacea. By M. Z. Grrser*, 
Vascular Apparatus.—The larvee of the Crustacea, whatever 
form they may present, are at first completely destitute of 
branchiz ; or if they possess them, these organs are quite rudi- 
mentary, and do not yet fulfil any function. Respiration, in 
this state, is performed by the whole of the general envelope. 
Even in the Lobsters, which are hatched with tolerably large 
branchie, the primitive respiration is absolutely tegumentary ; 
for these appendages are impermeable to the blood until the 
third moult ; and when they begin to perform their functions, the 
number of blood-globules which they admit is excessively small 
relatively to the mass of those which flow to the heart without 
traversing them. From this modification of the respiratory act 
there results a circulation of the greatest simplicity—the blood 
which the arteries have distributed in all parts of the body 
returns directly to the heart without passing through any special 
apparatus. 
The heart, of all the organs exhibited by the Crustacea at 
their birth, is that of which the general form undergoes the 
least amount of subsequent change. In the larvee it differs very 
little from what it is in the adult Crustacea; and it invariably 
occupies in the larve its definitive position, under the superior 
wall of the cephalothorax and above the pyloric portion of the 
intestine. In the Zoée (larve of Brachyurous Decapods) it is 
found immediately at the base of the temporary spine which 
rises from the middle of the thorax. 
With the exception of the larva of the Nymphon of our 
coasts}, in which | have never yet succeeded in seeing the heart 
distinctly, all the Crustacea of which I have been able to study 
the metamorphoses{ have the central organ of the circulation 
composed, at all ages, of two very distinct parts—one enveloped, 
the other enveloping, and bound together only by a few mus- 
cular bands, the action of which is manifested during diastole. 
The enveloped portion evidently corresponds with the arterial 
heart of the nigher animals. It consists of a sort of contractile 
* Translated by W.S. Dallas, F.L.S., from the ‘Comptes Rendus,’ 
April 23, 1866, pp. 932-937. 
+ The larva of this Nymphon is exceedingly curious, both in its external 
form and in its internal organization, and it differs from the adults as 
much as the Phyllosomes from the Palinuri, or the Zoé@ from the various 
Crabs to which they belong. The body is not at all articulated; and the 
true legs, which are only two in number, have only two joints and a ter- 
minal claw. I propose, however, to make them the subject of a special 
notice. 
+ See ‘Comptes Rendus,’ 26th December, 1864. 
