Blood of Australian Animals. 205 



The above differences in reaction to stain raises the question 

 aw to whether tho polymorphs of mammalia are strictly to be 

 compared with those of lower forms — a fact denied by Gruner, as 

 I have stated. 



(e) Eosinophils were few in amphibia, and frequently contained 

 large, round granules. They were also poorly marked in reptiles, 

 though in Chel. longicollis there were distinctly two kinds of 

 granules, some cells containing large spindle structures compar- 

 able to those of birds, and about half as numerous as the ordinary 

 foini, containing round granules. Eosinophil cells were much 

 more numerous in birds, and showed two kinds of granules in many 

 forms. They were few in number in monotremes, and never 

 exceeded 8 per cent, of the total number of leucocytes in marsu- 

 pials. 



Platelets were only apparent in mammals. 



Conclusion. 



There is a general decrease in size and increase in number of 

 red tells in ascending through the various vertebrate groups. 



There is a corresponding decrease in number, but increase in 

 size of the lymphocytes. The mononuclears remain fairly constant 

 in size, but decrease in numbers.. The reptilian relationship of 

 the monotremes is suggested by the similarity of the mononuclear 

 corpuscles in the two groups. The polymorphs also increase in per- 

 centage counts as we rise in the scale of vertebrates. The eosino- 

 phils are only really numerous in birds and the higher reptiles 

 (e.g., Chel. longicollis), where there are also two kinds of granules 

 — a round and a crystalloid variety — possibly pointing to an 

 avian relationship. The absence of those cells as Avell as that 

 of mast cells in the fish points to their being a specialised nature. 

 There is a slight decrease in the size of the eosinophils in passing 

 through the various groups, but it remains fairly constant. The 

 variations in reaction to staining of different classes of cells in the 

 various groups raises the question as to the homology of the 

 several types of leucocyte in vertebrate animals. 



EXPLANATION OF FIGURES. 



Figs. 1-G. — Porcupine Fish. Drawn with camera lucida. 1, Mono- 

 nuclear cell, stained with Giemsa. 2 and 3, Red Cor- 

 puscles, stained with Giemsa. 4 and 5, Lymphocytes, 

 stained with Jenner. 6, Polymorphonueleate cell, 

 stained with Giemsa. 



