CHYLAQUEOUS FLUID OF INVERTEBRATE ANIMALS. 
635 
aqueous fluid, no doubt can exist ; and as already maintained, the true-blood is repro- 
duced, at all events in part, out of the materials supplied by the chylaqueous fluid ; 
the conclusion is obvious that this latter fluid is incipient blood, and that conse- 
quently it must be gifted pro tanto with the property of nourishing the solid struc- 
tures of the body. But this inference is rendered almost certain by the force of the 
examples furnished by the Zoophytes, Medusse, &c., in which this fluid constitutes 
the only Jiuid element of nutrition in the organism. 
The chylaqueous fluid must however be regarded as in itself a manufactory; 
ITS corpuscles execute an office by which the mineral substances and proximate prin- 
ciples are vitally assimilated. In the Annelida (and therefore in the Entozoa and 
Echinoderrns) the corpuscles do in this fluid, as already explained, what in the 
higher Invertebrata and Vertebrata is accomplished by corpuscles, somewhat more 
definitively organized, floating in the true-blood. From these facts the physiologist 
may state, that under all circumstances, how simple soever the fluid may he, the agency 
of cells, either in the solids through which the fluids pass, or floating in the fluids 
themselves, is more or less essential to the vitalization of the liquid medium of nutri- 
tion. In the Annelida the true-blood is incorpusculated, because the cell agency is 
performed in the fluid, lower in grade than itself, which oscillates in the peritoneal 
cavity. If this fluid did not exist, then the corpuscles, solid cells, would probably 
have been present in the true-blood, there to enact their destined functions. 
From these observations the inference may be drawn, that between these two nutri- 
tious fluids, in the zoological series, there obtains a definite physiological balance ; 
that one is capable of absorbing or merging into the other, according as the observer 
ascends or descends the scale. The chylaqueous system ends above with the larva 
of Insects, and the true-blood system traced downwards terminates at the Echino- 
dermata. 
With reference to the nature of the function executed by the floating cells of the 
vital fluids, I may be permitted to mention here one fact, which, during the prosecu- 
tion of my recent studies, has excited in my mind a constant and eager attention. 
When the voluminous corpuscles of the chylaqueous fluid of the Annelida hurst in 
the field of the microscope, the semi-fluid contents of these bodies Jibrillate, i. e. 
coagulate as they flow out of the containing cells. This is a constant fact observed 
with the utmost exactness a thousand times. It is an absolute proof, addressed 
directly to the eye, that the contents of the cells, that which they themselves secrete, 
is a self-coagulating principle, is higher in organic properties than that in which the 
cells float, and which surrounds them externally, and out of which therefore their 
parietes must produce what their cavities circumscribe. Science does not demand 
a more satisfactory proof that the floating cells have for one of their offices that of 
generating^Z/r<«e ; another of their functions is that unquestionably of manufacturing 
pigment. 
Articulated Animals. — Arranged on the basis of the evidence drawn from the 
4 N 
MDCCCMI. 
