CHAPTER I 

 INTRODUCTORY 



Definition of a fish. Position in the animal kingdom. Difference between 

 fish and Cetacean. Classes of fishes. Numbers of species and indi- 

 viduals. The science of ichthyology. 



" These {the fishes) were made out of the most entirely ignorant and senseless 

 beings, whom the transformers did not think any longer worthy of pure respiration, 

 because they possessed a soul which was made impure by all sorts of transgression ; 

 and instead of allowing them to respire the subtle and pure element of air, they thrust 

 them into the water, and gave them a deep and muddy medium of respiration ; and 

 herwe arose the race of fishes and oysters, and other aquatic animals, which have 

 received the most remote habitations as a punishment for their extreme ignorarwe.'* 



Plato. 



It is of primary importance in a work of this nature to make it 

 clear from the outset exactly what is meant by a fish, for in 

 popular parlance the word "fish" is often used to include any 

 animal living in the water, a definition which appears in all 

 the older dictionaries. Although convenient, this can hardly 

 be described as scientifically accurate, including, as it does, 

 such diverse organisms as the Whales, Seals, Salmon, Oysters, 

 Cuttle-fishes, Star-fishes, Jelly-fishes, and Sponges, creatures 

 that differ from each other even more widely than do reptiles 

 from birds or birds from mammals. The aquatic animals just 

 mentioned, however, all fall naturally into two main categories 

 in respect of one important bodily feature — those with a 

 vertebral column or backbone and those with none. Man has 

 a backbone, and so have all the mammals, birds, reptiles, 

 amphibians, and fishes; all the others have no backbone. The 

 backboned animals or vertebrates are better known to most 

 people than the majority of the lower animals; indeed, with 

 the exception of a few Hke the oyster and lobster which are 

 eaten as delicacies, the invertebrate animals are regarded for 

 the most part with lukewarm interest, in some cases with actual 

 disgust. This attitude is partly explained by the superior size 

 of the vertebrates, by the greater ease with which they can be 

 observed and studied, and by the beauty of form and colour 

 displayed by many of the birds and mammals. It has been 



