

The Ottawa Naturalist, 



Vol. IX. OTTAWA, APRIL, 1895. No. 1. 



COLOURLESS BLOOD IN ANIMALS. 



By PROF. E. E. PRINCE, B.A., F.L.S., &c , Dominion Commissioner of Fisheries, 



Ottawa. 



We are so accustomed to think of that wonderful fluid, which 

 circulates through the blood-vessels of animals, as essentially a red fluid, 

 that it may be a matter of surprise to many that red blood is in reality 

 very exceptional in the animal kingdom. In all the various classes of 

 animals, irom the lowest to the highest, we recognize the remarkable 

 fact that colourless blood is most general. In the highest forms there 

 are corpuscles, coloured by that oxygen-loving substance, red haemo- 

 globin ; but the presence of this coloured matter is so uncommon in the 

 blood of the lower types, that examples of it are of extreme physiological 

 interest. Thus, the earthworm and the leech have red blood ; but the 

 presence of the red colour is not in the corpuscles, it is due to 

 h emoglobin in the serum or fluid. The fluid is red. but the a rpuscles 

 themselves, are colourless. Other worms (marine annelids) have 

 emerald green blood, others yellow : but in most the fluid is destitute of 

 colour. It is the same amongst insects, and arthropods generally. The 

 heart, which passes down the back in these creatures, drives a clear 

 corpusculated fluid over the body. Remarkable exceptions amongst 

 these may be noted, however. Thus, a small Dipteran fly, Chironamus^ 

 in its aquatic larval condition, is of a brilliant vermilion hue, due to the 

 red blood visible through the transparent walls of the worm like body. 

 Such exceptions only emphasi/e the fait more strongly that colourless 

 blood prevails. Anyone who has studied the anatomy of a starfish, has 

 noticed below the intricate water vascular system, a central ring or blood 

 el encircling the mouth. This blood-ring is clear and transparent : 

 and sends off a translucent radial blood vessel to each arm. The fluid 



