o<jo Gwynneth Buchanan: 



blood platelets or thrombocytes in the frog, but I have found 

 nothing to correspond strictly with these cells in appearance out- 

 side the mammalia. 



Bed Corpuscles. — These approached very nearly the actual num- 

 ber per c.mm in human blood. There was a marked decrease in 

 the size of the cells as compared with in vertebrates; and in all 

 cases they were non-nucleated, bi-concave discs. The variation in 

 diameter is also much less than in other groups (5.1 fi/I. 8 ft). In 

 the young platypus (0. anatinus) they showed the greatest range, 

 running from 6.6/i-9.9//.. There seemed to be no definite relation 

 between the age of the animals and the size of the corpuscles. Poi- 

 kilocytosis was fairly common in many marsupials, as well as poly- 

 chromatophilia, while normoblasts were frequently present. 1 



There were also, in the smears of marsupial blood, a large 

 number of corpuscles of normal shape, but small size (microcytes). 



Lymphocytes averaged very much larger than the corresponding 

 cells in birds, the greatest diameter being found in one species of 

 wombat (Phascolomys), but there was no marked tendency towards 

 increase in size in the young. The percentage counts varied 

 i aormously, running as high as 72.0 per cent, of the total leuco- 

 cytes in Trichosurus vulpecula; but I could find no definite rela- 

 tionship between age and numbers, though, as a general rule, tin- 

 young forms showed a high percentage count. In T. vulpecula and 

 others the nuclei of some lymphocytes appeared to be distinctly 

 dividing, and the size and amount of protoplasm in relation to the 

 nucleus varied. 1 mt apparently the lymphocytes were non-granular, 

 tints differing from the mononuclear forms. In Petaurus breviceps 

 the lymphocytes were divided into two classes — (a) small, with very 

 distinct outline to the nucleus, and very little cell substance; (In 

 larger (••ells, with less clearly marked nuclei, and protoplasm barely 

 Bhowing let'. Gruner). In the young echidna the lymphocytes 

 varied much in size, and were very granular; while the nuclei 

 of several in the wombat smears showed distinct lobing, giving a 

 kidney-shaped appearance. (Transitional forms?). 



Mast celh were very rare, being only observed in T. vulpc- 

 cula and the wombat, and in neither case numbering as much as 

 I per cent, of the total leucocytes. 



Mononuclear <■<!!.< were divisible in BOme cases into small ami 

 large, and averaged as a rule, larger than the polymorphs- They 

 showed, particularly in the young platypus, a great variation, as 



1 Oleland and Johnston (::) suggest this may lie an archaic feature. 



is Mid ( hristopher (0) remark on the frequent occurrence of "intermediate leuco- 

 cytes." mi.l u.n between ti„ large and small mononuclear cells. 



