III. — On the Vascular and Nervous Apparatus of the Larva of 

 the Marine Crustacea. By M. Z. Gerbe*. 



Vascular Apparatus. — The larvge of the Crustacea, whatever 

 form they may present, are at first completely destitute of 

 branchiae ; 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 

 branchiae, 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 larvae it diff"ers very 

 little from what it is in the adult Crustacea ; and it invariably 

 occupies in the larvae its definitive position, under the superior 

 wall of the cephalothorax and above the pyloric portion of the 

 intestine. In the Zoe(E (larvae 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 

 coastsf, in which 1 have never yet succeeded in seeing the heart 

 distinctly, all the Crustacea of which I have been able to study 

 the metamorphoses J have the central organ of the circulation 

 composed, at all ages, of two very distinct })arts — 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 higher 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. 



t 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 Zoece 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. 



X See ' Comptes Rendus,' 26th December, 1864. 



