638 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
They relate however rather to the mechanism of the fluid’s orbit than to the com- 
position of the fluid itself. They cannot therefore be rendered subservient to the 
objects of the present communication. Mr. Bowerbank’s observations* on the 
blood of Insects stand alone, and deserve implicit confidence. “The blood (of 
insects), which is usually of a very transparent greenish or yellowish colour, is filled 
with a great number of little particles, which were described by Carus as oblong or 
oval, but more correctly by Mr. Bowerbank as flattened oat-shaped masses which 
retain their form while circulating through the body, but like the particles of blood 
in Vertebrata, become globular immediately they are brought into contact with water. 
It is stated by Burmeister that they vary in diameter from - 2 ^ to 2 -g-oth of a line ; 
but they differ also in size in the same individual, and are often rough and tuber- 
culated, as noticed by Edwards, and as distinctly seen in the blood of Sphinx ligustri^," 
The preceding paragraph embraces the sum of our present knowledge on the histo- 
logical character of the nutritive fluids of insects ! It is impossible in the present 
limited communication to exhaust the materials comprised within a field of observa- 
tion so vast and various. Among species so diverse and boundless the fluids must 
be characterized by corresponding varieties in physical characters. This is probable 
from the analogy derived from the examination of the fluids of the annulose series. 
It will accordingly be found, that although specific distinctions in the corpuscular 
elements of the fluids in the class “ Insecta” are not unequivocally drawn as in the 
Annelida, under a marked typical unity for the whole class, specific diversities will 
notwithstanding be remarked to prevail. These varieties however are extremely 
obvious in the chylaqueous fluid of the larvae of the several component species of 
the class. 
Chylaqueous Fluid of the Larvce of Insects.— At the first emergence of the larvce of 
several species of insects from the ovum, no dorsal vessel is yet formed. The visceral 
space is filled with a fluid perfectly colourless, which fluctuates irregularly in the con- 
taining cavity and is charged with corpuscles, which vary histologically in different 
species. As every larva does not emerge out of the ovum in the same stage of develop- 
ment, the floating cells of the chylaqueous fluid will be found to present differences 
depending rather upon age than upon species. The accompanying illustrations, 
which are drawn with repeated and exact care, represent several examples of these 
floating cells as they occur in the principal species of water-larvse, (figs. 44 to 51). 
I have also noted with every practicable accuracy the characters of the bodies 
observed in the fluids of the larvae of the Neuroptera, Hymenoptera, Lepidoptera 
and Coleoptera, with the uniform result of discovering that (until a very advanced 
period of the larval stage) they foreshadow in no one particular those which after- 
wards appear in the blood of the perfect insect. In the chylaqueous fluid of the larva 
of the Hay Moth {Leptona Candida) they consist of oblong flat cells, exceeding in 
* Entomological Magazine, vol. i. April 1833. 
t Art. Insecta, by Mr. Newpokt, Todd’s Encyclopedia. 
