No. 39—1889.] zoological tables. 25 



Let us suppose the thoracic ventrals to be represented by 

 the letter a, the abdominal by b, the jugular by C; the spiny 

 vertical fins by a, the soft by b ; the ctenoid scales by a, the 

 cycloid by b ; then we could see the relationships of all 

 known bony fish to each other, with regard to these particular 

 characters, by constructing a table like the following : — 



Ventrals. Vertical Fins 



Perch 



a 



a 



a 



"Wrasse 



a 



a 



b 



Gray Mullet .. 



b 



a 



b 



Carp 



b 



b 



b 



Cod 



c 



b 





Scales. 



The letter a might, however, represent far more than the 

 mere position of the ventrals : it might stand for those in 

 which the membrane is supported by one spine and five 

 branched rays placed on the thorax ; b for those which have 

 the same character but which are placed on the abdomen, 

 and so on. And the same principle can be applied to all the 

 other parts, external or internal, of fish or any other animals. 

 This is the application of the "Natural Method" to the 

 parts of animals considered separately. The "Natural 

 Method " is thus defined by Cuvier : — " There is but one 

 perfect method, which is the natural method. We thus call 

 an arrangement in which beings of the same genus will be 

 closer together than those of all other genera, genera of the 

 same order than those of all other orders, and so on." 



The theory of the construction of such tables is perfectly 

 simple. The student, having provided himself with a collec- 

 tion of some group of animals, either from all parts of the 

 world where they are found or from some particular locality, 

 studies first one part, such as the wing in birds or ventral 

 fin in fish, and groups those species together which agree in 

 having those parts of the same character ; he then proceeds 

 to the consideration of the other parts, one by one, until he 

 has exhausted all the characters employed in the diagnosis 

 of the particular group he is describing. Then, as in the 

 little table above, each different type of wing or fin, or any 



