VESTIGIAL STRUCTURES. 89 
if not entirely, due to the gradual acquisition of 
terrestrial habits by animals originally aquatic, is 
largely supported by the condition of the pinna in 
aquatic mammalia. The adult whale has no pinna or 
external auditory meatus ; Howes has detected vestiges 
of the pinna in the embryo of the white whale (Beluga 
Jeucas): the pinna was almost microscopic in size 
My 
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Fic. 46.—The head of a Seal (Ofaria gtllespiz), showing the 
small pinna. (After Forbes.) 
and pointed, resembling in a very striking manner the 
small cervical auricles in man. 
In most seals the pinna are wanting, and when 
present they are short, pointed, and vestigial, as in the 
eared-seals (Oftaride), fig. 46. 
If the Cetaceans and Phocide are to be regarded as 
land mammals which have taken to the water—which 
is the most consistent manner of studying them—we 
