Zoological Society. IW)1 



the Oviparous Vertebrata, for example, there are often many grada- 

 tions of form, from the well-marked and prevailing ellipse, to the 

 longer or shorter oval or even circular figure ; and in any mammal 

 some of the corpuscles are a third larger and some a third smaller 

 than the mean size. 



Mammalia. 



Various sizes of the corpuscles. — ^l^he corpuscles of the Elephant 

 are the largest yet known ; then follow those of the Sloth and of the 

 Whale. The Napu Musk Deer has the most minute corpuscles ; 

 those of the Stanley Musk Deer are nearly as small ; those of the 

 Ibex of Candia are larger ; and the next increase of size is in those 

 of the Goat. Before my observations, the corpuscles of the last- 

 named animal were the smallest known. 



Size of the corpuscles in relation to that of the animal. — The smallest 

 British mammal, the Harvest Mouse, has corpuscles quite as large 

 as those of the Horse ; in the Common Mouse they are larger than in 

 the Horse or Ox. But although there is no relation between the 

 size of the corpuscle and that of the animal in different orders, in the 

 same order the larger species have generally larger corpuscles than 

 the smallest species. Thus, in the large Ruminants the corpuscles 

 are distinctly larger than in the smallest Ruminants, and the same 

 fact is observable of the Rodents. In these examples the gradation 

 in the size of the corpuscles may not exactly follow that of the ani- 

 mals, but none of the very small species have corpuscles so large as 

 those of the largest species. 



Size of the corpuscles in the same animal at different periods of life. 

 — In very young embryos the corpuscles are much larger than in the 

 adult, and in such embryos each corpuscle has a nucleus, which dis- 

 appears at a later period of intra-uterine life, when the corpuscles 

 are yet larger than those of the mother. At a still later period they 

 become so unequal in size that it is difficult to say whether they be 

 larger or smaller in the fcetus than in the adult. In a kid twelve 

 days old, bred between an ibex and a goat, I found the corpuscles 

 larger and more variously sized than those of either of its parents. 



The thickness of the corpuscles is variable ; but it is commonly 

 somewhat more than a fourth of the diameter. 



Size of the corpuscles in different Orders. — The Monkeys have cor- 

 puscles pretty uniform in size, generally just perceptibly smaller 

 than those of Man ; in some of the Monkeys of the new world the 

 corpuscles are slightly smaller than in the Monkeys of the old world, 

 and in the Lemurs somewhat smaller still. In the corpuscles of the 

 different subdivisions of the Ferte there is such a well-marked diver- 

 sity of size, that the fact* might be used as a help to classification. 

 The families, set down in the order of the size of their blood-discs, 

 stand as follows : Seals, Dogs, Bears, Weasels, Cats, Viverras. It 

 is commonly most easy to distinguish a viverra, by the comparatively 

 small size of its blood- corpuscles, from a seal, dog or bear. Among 

 genera of doubtful affinities, if regard were paid to the blood- 



* It has recently been enlisted into the service of natural history by Mr. Jesse, 

 in his interesting Anecdotes of Dogs. 



