96 A BOOK OF WHALES 



characters are quite sufficient for the present purpose ; 

 many might be added to them of course. No 

 creature which has these characteristics is anything 

 but a mammal. One or two of them are wanting 



o 



in those lowest of the mammalian tribe the Orni- 

 thorhynchus and Echidna ; they do not bring forth 

 their young alive, but lay eggs ; still, when born the 

 young Echidna and Platypus are nourished by milk. 

 Fishes a very few of them may have what are 

 believed to be the representatives of lungs, and with 

 which, indeed, they actually breathe ; but they have 

 also gills, and the vast bulk have no breathing organs 

 except these gills. Lungs are found higher in the 

 series, but no diaphragm like that of whales until 

 we get to mammals. 



But to go further than this, and to decide where- 

 abouts in the longr series of mammals the whale tribe 



o 



should be intercalated, is a matter which is at present 

 beyond our knowledge. We may, however, discuss 

 the matter for a little in order to show the grounds 

 of our ignorance. 



o 



From the sketch which has just been given of the 

 outward form and the internal structure of whales, it 

 will be apparent that the nature of the medium in 

 which they live has profoundly affected the characters 

 of the different organs. There is positively no part 

 of the body, with the exception perhaps of the brain 

 and the stomach, and one or two other points to be 

 referred to later, that has not been evidently altered 

 in some way, more or less, in different cases, to meet 

 the changed conditions of life as we believe them to 



