CHYLAQUEOUS FLUID OF INVERTEBRATE ANIMALS. 
037 
the development of any special power for directing and sustaining its movements. 
This fluid is at first almost destitute of floating cells, which consist only of oleous 
molecules. In process of growth corpuscles, more or less resembling those afterwards 
to be described as present in the blood of the adult Myriapod, begin to appear, and 
pari passu with this genesis of definitively organized corpuscles the structure and 
function of the dorsal vessel assume a more obvious presence. This embryonic system 
of fluid, before the appearance in it of the permanent corpuscles, and before the deve- 
lopment of the tracheal system, undergoes the process of aeration in accordance with 
the plan on which this great function is performed under the chylaqueous type. Less 
complexly organized than the blood-proper, it demands no special apparatus for its 
exposure to the aerating medium. As it rolls in the general cavity of the body, it 
undergoes adequately this vital change. These observations require very little to be 
modified to render them true of all insect-larvse. Thus, then, there exists in the 
Myriapod ‘a circulating fluid’ anterior to the true-blood, which the latter gradually 
supersedes, and ‘a respiration’ which precedes that which subsequently devolves 
upon the tracheal system*. 
In the adult Myriapod the blood is colourless and richly corpusculated. The cor- 
puscles are perfectly destitute of colour. This fact is true of the fluid systems of all 
articulated animals without a single exception. Wherefore this universal absence in 
the fluids of a pigment-producing faculty? The floating bodies of the blood in the 
adult Myriapod are regularly and deterrninately organized. They are nearly the 
same in the lulidae as in the Scolopendrse, the highest and the lowest orders. They 
present under the microscope, in a fresh drop of blood, three leading varieties : — 1st, a 
large pellucid nucleus surrounded by a few granules (Plate XXXII. fig. 38) ; 2nd, the 
orbicular, in which the granules have grown in number, abnost concealing the nucleus 
(fig. 39) ; and 3rdly, the ovoid or oat-shaped, in which the nucleus has reappeared 
(fig. 40). In none of these bodies is it possible under any manoeuvre to detect the 
presence of a cell-capsule. The molecules surrounding the nucleus seem rather to be 
drawn to the latter by a mysterious centripetal power, than embraced by an invo- 
lucrum. These bodies, when they burst in the field of the microscope, 
proving that the molecules are held together by a tenacious self-coagulating principle. 
Insecta. — Contributions, from several authoritative observers'!', towards a better 
understanding of the circulation of Insects, have appeared during the last two years. 
* “The history of the development of the embryo of the Myriapod presents a remarkable resemblance to 
that of the true Annelid ; for the embryo at the time of its emergence from the egg possesses but a very small 
number of segments ; and these continue to increase by the repeated subdivision of the penultimate segment 
until the number characteristic of the species has been attained.” — Principles of General and Comparative 
Physiology, by Dr. Carpenter, 3rd edit. 1851, p. 375. 
t Etudes Anatomiques et Physiologiques et Observations sur les Larves des Libellules, par M. Leon Dufour, 
Annales des Sciences Nat. 1852. Nouvelles Observations sur la circulation du sang et la nutrition chez les 
Insectes, par Emile Blanchard, op. cit. 3”"® Serie, 1851. Note sur la circulation des fluides chez les Insectes, 
par ie Professeur Louis Agassiz, op. cit. 3™® Serie, 1851. 
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