39 



exhibited by Ceratodus forsteri, show enormous red cells, 

 varying from 36 to 41'o jm by 20*7 /x. 



Amongst the Tehosfonii , the red cells are much smaller, 

 being sometimes nearly spherical, some of the latter being 

 7 to 8 /x in diameter and in other species 12 ju-. The usual 

 size, however, of the red cells of these fishes seems to be about 

 10-4 to 12 by 8 to 9 /x. 



These figures seem to indicate that with later specializa- 

 tion has eventually come, both in fishes and birds, a diminution 

 in size of the red cells. The cumbersome corpuscles of 

 {' eratodus have doubtless pla3^ed a part in the gradual extinc- 

 tion of the Dipnoan fishes. The relationships of the various 

 classes to each other is clearly shown in the size of the red 

 •cells. The red cells of the Elasmobranchs approximate more 

 in size to those of Batrachians and Reptiles than do the red 

 corpuscles of Teleostean fishes, which latter do not link on to 

 any of the higher vertebrate stems. The enormous red cells 

 of the Dijmoi approach those of such Amphibians of the order 

 Urodela as Proteus (said to be 58 x 35 /u,) and Amphiuma 

 (given as 77 X 46 /x). In the frogs and reptiles the size has 

 diminished somewhat, whilst in the birds, the "oldest" forms 

 show distinctly a tendency to larger cells than the more 

 specialised ones, the smallest being met with in some families 

 of Passerine birds. The results of the measurements of the 

 Ted cells of a large number of Australian birds seem to indicate 

 that such may be of some help in ascertaining the broader 

 relationships of some aberrant species. 



Table of the Sizes of the Red Corpuscles of Various 

 Australian Vertebrates. 



(The sizes given are in micromillimetres (1 /1000th of a 

 millimetre). The first figures given indicate the length and 

 breadth of the cells, the second the same dimensions of the 

 nucleus, if present.) 



MAMMALIA. 



Order Chiroptera. 



Tteropus gouldi (Gould's fly- 

 ing fox) 5'2to5'7 



ChaUnolohus gouldi (Gould's 



bat)[?] o'oto6-o 



Subclass Metatheria. 

 Suborder Diprotodontia, 

 Macropus ualahatus (black- 

 tailed wallaby) 8 



Subclass Prototheria. 

 ^Echidna aculeata 6*6 to 7 



6-8 



