DESCRIPTION OF PLATES. 313 



FIG. 9, Their size in a frog. 

 FIG. 10, Their size in a skate. 

 FIG. 11, Their size in a lobster. 



FIG. 12, The vesicles of the same lobster, as they appear 

 after being a short time exposed to the air. 



FIG. 13, The size of the globules of milk. 



marked examples of a difference of shape in the blood-corpuscles of 

 nearly allied animals occur among birds : the snowy owl, the passenger 

 pigeon, the butcher bird, are all distinguishable by the longer oval 

 form of their blood-corpuscles from their congeners. See Note xcvin, 

 pp. 218-19. 



