CHYLAQUEOUS FLUID OF INVERTEBRATE ANIMALS. 
623 
with the more recent contributions of M. Quatrbfages towards the study of the 
difficult subject of the anatomy of the Annelida. In the analysis of his memoirs* I 
have endeavoured conscientiously to assign to the versatile g'enius of this French 
naturalist the real merit with reference to this subject to which it is entitled. I have 
shown, I trust correctly, to what a very limited distance the parallelism continues 
between both the researches and the conclusions of M. Qcjatrepages and my own. 
One important difference between our observations, severally, should be here un- 
equivocally defined. He states that in a// Annelida the “ fluid of the visceral cavity” 
is circulated by means of the vibratile cilia by which the cavity in question is lined. 
1 have affirmed the very contrary of this statement as the uniform result of my inves- 
tigations. In no Annelid whatever, the Aphrodite excepted, is the cavity containing 
the chylaqueous fluid lined by vibratile epithelium. Cilia exist on the mternal 
hollows at the bases of tbe feet, and on the tentacles of a few species only. 
It is only possible in the larger species to obtain a sufficient quantity of the peri- 
toneal fluid for the purposes of chemical analysis. In Arenicola, Terehella nebulosa, 
T. conchilegia, and the largest Nereids, it may be readily collected for examination. 
In these species it exceeds sea- water in specific gravity, being from 1‘032 to 1’034, the 
water from which they were taken being 1*028. Salt water being the basis of this fluid 
in the Annelida, the superaddition to it of fluid and solid organic principles accounts 
for the high density of the peritoneal fluid in these animals. On standing a distinct 
coagulum is precipitated, carrying with it the corpuscles. By the coagulum the 
presence of fibrine is announced, and that of albumen is distinctly proved by the 
addition of nitric acid ; slow evaporation yields a rich crop of the cubes and octahedra 
of the chloride of sodium. The morphotic elements vary in a remarkable manner 
in different species ; that is, for the same species, the individuals being different, the 
corpuscles of the chylaqueous fluid are constant, and nearly the same in microscopic 
characters for every season of the year. In different species therefore these solid 
elements of this fluid, like the corpuscles in the blood of vertebrated animals, become 
signs of specific distinction, but the specific variations are much less marked than the 
generic. In the case of the Annelids, it is susceptible of demonstration that the float- 
ing cells of the chylaqueous fluid vary in apparent structural characters with the age 
of the individual. For some time after the emergence of the young from the ovum and 
before the development of the branchial, pedal, and tentacular appendages, the chyl- 
aqueous fluid is a limpid, transparent, wow-corpusculated liquid. It bears not a trace 
of floating corpuscles. This fact is full of interest. As the worm progresses in growth, 
so the corpuscles slowly appear in the chylaqueous fluid. The blood and the blood- 
system are produced before tbe floating cells are generated in the chylaqueous fluid. 
The conclusion is evident. In the young Annelid the agency of the floating corpuscles 
of the chylaqueous fluid is not required either for the elaboration of the fibrine or the 
production of the pigment of the blood-proper. But it is important to guard against 
* See ante. 
