70 Miscellaneous. 
4. However the larvee of various species of Crustacea may resemble 
each other in external form, nevertheless in the arrangement, the 
form, and the number of the spots of the skin and intestine, and 
especially in the number and conformation of the provisional appen- 
dages which adorn the extremity of the last segment of the abdomen, 
they present definite characters which enable us to say to what 
species any particular larva belongs. 
5. The stomach of the larvee of the marine Crustacea presents 
no solid piece adapted to the grinding of food ; it is merely furnished 
on its inner face with rigid spinules arranged in rows, and with vibra- 
tile cilia like those found in the stomachs of a great number of the 
lower animals. These cilia communicate an incessant movement of 
rotation to the organic molecules upon which the animal feeds. 
6. In all larve of Crustacea, the liver, at first reduced to two 
simple ceeca, one on each side, is manifestly a diverticulum of the 
intestinal tube, with which it has wide communications ; by ramify- 
ing, it forms a hollow tree, at the base of which we may see oscillating 
the vitelline globules which the umbilical vesicle pours into the 
pyloric portion of the intestine. 
7. The marine Crustacea, however the respiratory functions may 
be ultimately performed, all have a tegumentary respiration in the 
larval state. 
With the exception of the Lobsters, which, when first hatched, 
have a rudimentary branchial apparatus quite unfit to perform any 
functions, the larve of the other genera of Crustacea enumerated 
above are absolutely destitute of this apparatus; some, indeed, do 
not present any traces of it until after several moults. 
8. The want of the function of branchial respiration necessitates 
a radical difference between the circulation of the individual in the 
larval and the individual in the perfect form—that is.to say, having 
acquired branchie. In all the larvee of Maza, Porcellana, Crangon, 
Palemon, Palinurus, Homarus, Cancer, &c., the blood which the 
arteries have distributed to the different parts of the body returns 
entirely, directly to the heart, and this condition persists for a con- 
siderable time. It is only after the third moult, in the most perfect 
larva of the species inhabiting our seas—that of the Lobster—that a 
few globules are diverted from the original general circulation to 
penetrate into the nascent branchiz. 
g. All the arteries open directly into the venous passages by an 
aperture more or less bevelled and more or less dilated into a trumpet- 
like form. 
10. In some larve the abdominal artery may present a sort of 
sphincter in its course, at some distance from the central organ of 
circulation ; this, by contracting, temporarily suspends the flow of 
blood to the hinder parts*. 
* This remarkable peculiarity exists not only in the larvee of the Lob- 
sters, as already indicated, but also in those of the Porcellane. tis even 
probable that it will be found in many species, and perhaps in all; for 
when we observe the circulation in the last segment of the abdomen of 
larvee of Cancer, Carcinus, Palemon, &c., interruptions are perceived in it. 
