640 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
first nutritive embryonic fluid of the Insect undergoes respiration on the aquatic, not 
on the atmospheric plan, conforming in this fundamental particular to the law 
governing the function in all ehylaqueous fluids. 
Blood-proper of Insects. — As already stated, Mr. Bowerbank was the first to 
describe with exactitude the morphous solids of the blood of insects. But unfor- 
tunately for science his observations were instituted only on one species. No phy- 
siologist has yet rightly estimated the importance attaching to the history of the fluids 
in the animal series — not the cavities and channels and vessels in which they move, 
but the fluids themselves, histologically, morphologically, chemically, teleologically, 
as component elements of the living organism. No zoologist is yet prepared for the 
assertion, that throughout the true articulated series there prevails hut one f undamental 
type of hlood-corpuscle. The variations from this essential unity, coinciding with 
differences of class, order, genus or species, are never so deeply inscribed as to 
involve a departure from this type. It begins at the adult insect, and is unequivocally 
traceable through the intermediate forms of the Entomostraca, Crustacea, and Cirrhi- 
peda, ending at the Arachnida. Here is a novel and unexpected confirmation of 
those affinities which are founded upon the resemblance of the solid parts. In the 
character of the fluids, the classifier is henceforth furnished with a new and important 
means of determining zoological differences and resemblances. 
The blood of the perfect insect is colourless, and charged with colourless floating 
cells. It is impelled in a definitive orbit by a special power, — a dorsal vessel. Through- 
out the whole class its morphous elements consist of cells of peculiar construction. 
There is a conspicuous nucleus in each cell. It is surrounded by minute, pellucid, 
very slightly refracting granules. On bursting, these corpuscles Jihrillate. It is not 
possible to detect separately the cell-capsule ; though, from the constant and definite 
figure of the bodies, it admits of no dispute that a distinct involucrum exists. The 
figure varies from the orbicular to the oval or oat-shaped. They are flattened ovals, 
not cuhically oval. They are almost immediately destroyed by water. The first phase 
is the pellucid molecule ; the second an orbicular granular particle ; the third the 
flattened oat-shaped cell. In every species of insect yet examined, the extremes of 
variations in form are bounded on one side by the orbicular, on the other by the 
fusiform. The fundamental form is the compressed oat-shaped. The illustrations 
(figs. 40 to 43 ) exhibit with strict fidelity the structural characters of these bodies. 
They are amplified 420 diameters. 
Crustacea.— T\\q fluids of the Entomostraca are supplied with corpuscles which 
fall under the articulate type already indicated. They are, however, more generally 
circular (figs. 52 to 55 ), always bearing a nucleus more or less discernible, and filled 
with minute granules. In Branchipus, Daphnia and Cyclops, they answer with exact- 
ness to the preceding description. They are not numerous relatively to the bulk of 
the fluid. In these little crustaceans, in the adult state, the circulating system is 
quite as simply constituted as that of insects. The dorsal vessel is the moving power ; 
