204 Gwynneth Buchanan : 



Summary. 



Red Corpuscles. — Miss Clay-Pole (12) notes the decrease in size of 

 red evils in passing from generalised to specialised types, and asso- 

 ciates this with an increased haemoglobin capacity. I have found 

 the same fact borne out by my observations, as well as a correspond- 

 ing increase in the actual number of red cells, which, by increasing 

 ill.- total surface of the reel cells, augments the area over which 

 oxygen may be absorbed. There was a tendency towards larger size 

 in young forms, which was, however, hardly apparent in mar- 

 supials. Spindle cells, when present, tended to be polychromatic or 

 basophil in reaction, and were only found in any number in am- 

 phibia and reptiles. 



Leucocytes. — (a) Lymphocytes, as a general rule, seem to be- 

 more numerous in young forms. The size was also greater in the 

 young, and increased in passing through the various groups, being 

 largest in marsupials. This large size in the young is evidently a 

 reversion to the primitive type. 



(b) Mast cells seemed to be more characteristic of the lower groups, 

 as they were observed only once in marsupials, though they were- 

 numerous in reptiles. 



(c) Mononuclears were more numerous in young animals, 

 and the only form of white corpuscle found in the tadpole was 

 nearest this type — primitive, according to Gruner. The average 

 number of these cells became much less in monotremes and marsu- 

 pials. In amphibia there were three distinct classes, according to- 

 the sizes, a giant type being well marked in the young. In reptiles 

 only two classes were apparent, and the average size in the adults 

 was lvss than in amphibia ; while in birds they were smaller again, 

 but still of two kinds. Monotremes resembled reptiles; but in 

 marsupials we find otic size with no marked difference between the 

 young and adult. 



(d) Polymorphonuclears in amphibia were not easy to distin- 

 guish from mononuclears by staining, and were also few in num- 

 bei ; loth facts being more clearly marked in the young. In 

 reptiles also they were not clearly differentiated, and were only 

 distinct in one bird. In monotremes, and still more in marsupials, 

 they were numerous and apparent, except in the case of the adult 

 female Petaurus breviceps, which was suckling its young when 

 the smear was taken. Perhaps this fact may account for the 

 extraordinary decrease in polymorphs, and rise in number of 

 mononuclears in this particular specimen. 



