CHYLAQUEOUS FLUID OF INVERTEBRATE ANIMALS. 
633 
parfaitement distincts et reguliers, Le liquide hii-rneme etait incolore. Ici les glo- 
bules ofFrent la plus grande ressemblance avec ceux des Vertebres. Ce sont de petits 
disques aplatis de de millimetre environ,” &c. In this statement M. Quatre- 
FAGES is incorrect in attributing these ‘globules’ to the blood-proper, for the blood 
of this worm, like that of all Annelida, is destitute of every kind of globules ; it is 
perfectly fluid. The corpuscles exist only in the chylaqueous fluid, but the descrip- 
tion of them, as conveyed in the preceding quotation, is by no means exact. 
In general no distinction into venous and arterial blood is detectable, the plan of 
the Annelidan circulation rendering such a distinction almost impossible. The 
colouring elements are in all cases fluidified and uniformly blended with the fluid 
mass of the blood. The colour therefore must be developed in the ^wic?-mass, and 
that too without the intervention of any corpuscular agency, since the true-blood, as 
already stated, contains no solid cells. 
Glycera alha and Clymene arenicoida only excepted, the corpuscles of the chyl- 
aqueous fluid in ALL Annelids are destitute of colour. It is not chemically impossible 
that the coloured ingredients may exist in this latter fluid in a colourless state of 
coujbination, and that these ingredients, through entering into new combinations, 
may become brightly coloured after transition into the true-blood. 
In consequence of the impracticable minuteness of the quantity, no direct chemical 
analysis of the blood in the Annelid can be executed. As to the colour, however, 
analogy removes all doubt that the red tinge is due to the salts of iron and the green 
to those of copper. In those species of which the blood is light yellow, opake, milky, 
or lymph-like, it does not follow that the salts of the coloured minerals are altogether 
absent : they may exist under colourless combinations. To the physiologist it cannot 
be unimportant in this place to demand, if the blood-proper of the great majority of 
Annelids be a non-corpusculated limpid coloured fluid, and the chylaqueous fluid a 
colourless corpusculated liquid, in what manner, by what agency, does the blood 
acquire its colour ? If it be destitute of floating cells, the production of the pigment 
cannot be ascribed to the agency of the latter bodies. And if this pigment do not, 
at all events in a visible form, exist in the chylaqueous fluid, it must be developed 
during the passage of the latter into the blood-vessels (for, as will be afterwards more 
fully explained, the contents of the blood-proper system are derived by direct absorp- 
tion from the great reservoir of the chylaqueous fluid). From the obviously con- 
nected sequence of these events the inference is clearly deducible, that the parietes 
of the blood-vessels impress upon the fluid in transitu a chemico-vital change, which 
eventuates in the evolution of pigment. In other language, the walls of the blood- 
vessels, under the circumstances indicated, accomplish what in the instances of Glycera 
alba and Clymene arenicoida, and it may be prophetically added in all Vertebrata, is 
performed by the involucra, the cell-capsules of the floating corpuscles. One other 
lesson of extreme value is read to the zoo-chemist by the history of the blood in the 
Annelida. It is a limpid, non-corpusculated coloured fluid. In many species it 
