10 M.Z.Gerbe on the Vascular and Nervous Apparatus 
The venous circulation in the larve, as in the perfect animals, 
is rather lacunar than vascular. The blood which the arteries 
have distributed to all parts of the body, returns indeed by 
constant and determinate courses; but these courses consist of 
a succession of cavities which the organs leave between them, 
cavities in which it is difficult to ascertain the existence of 
proper walls or of regular forms. Thus this mode of circulation 
baffles description. All that can be said in a general way is, 
that three principal perfectly limited currents, two anterior 
and lateral and one posterior and median, open into the 
heart. The two former, in the Phyllosomes, are caused by the 
fluids which circulate in the cephalic buckler alone ; the third 
is formed by those which arrive from the true feet, the thorax, 
and the abdomen. In the larvee of the other Macrurous Deca- 
pods and in those of Brachyura, on the contrary, the fluids dis- 
tributed to the head and thorax combine to form the lateral 
currents, whilst the posterior current 1s produced solely by the 
blood returning from the abdomen. 
The Blenents of the blood in the first age of the Crustacea 
consist of a perfectly colourless liquid, and small, isolated, dia- 
phanous corpuscles, some oblong or square, others angular or 
virguliform, with the outlines very distinct, but always very 
irregular, even when these kinds of globules affect a more or less 
rounded form. 
Nervous Apparatus.—The nervous system of the larve of the 
Crustacea is composed, like that of the perfect individuals, of a 
double series of ganglia or medullary masses, in which the 
nerves of all parts of the body terminate. United to each other 
by longitudinal cords, these ganglia, which are the more volu- 
minous in proportion as the organs of the life of relation to 
which they correspond are more developed, form a continuous 
system upon the median line, extending from the base of the 
ocular peduncles to the last joint of the abdomen. Neverthe- 
less, taking into consideration the regions occupied by it, the 
central nervous apparatus may be divided into a cephalic, 
thoracic, and abdominal portion. 
The cephalic portion, or brain properly so called, is composed, 
both in the Phyllosomes and in the Zoé@ and other larve of 
Macrurous and Brachyurous Decapods, of a single ganglionic 
mass, situated between the bases of the rudimentary antenne 
and symmetrically divided into three unequal pairs of lobes, 
each of which furnishes a sensorial nerve. From the two 
anterior lobes spring the optic nerves, which pass directly into 
the ocular peduncles; from the two middle ones arise the inner 
antennary nerves, and from the two posterior the nerves which 
are distributed im the outer antenne and to the auditory organ 
