io THE MODERN STUDY OF ZOOLOGY 



A. Cor biloculare biauritum, sanguine 



calido rubro. 



1. Viviparis. Mammalia. 



2. Oviparis. Aves. 



B. Cor uniloculare uniauritum, san- 



guine frigido rubro. 



1. Pulmone arbitrario. Amphibia. 



2. Branchiis externis. Pisces. 



C. Cor uniloculare inauritum, sanie 



frigida alba. 



1. Antennatis. Insecta. 



2. Tentaculatis. Vermes. 



Of morphological classifications there are two 

 principal varieties, classification by definition and 

 classification by type. The Linnaean classification 

 is a typical example of the former of these. In it 

 the whole animal kingdom is divided up into groups 

 of convenient size, each characterised by the pre- 

 sence or absence of some one, two or more easily 

 recognisable features ; stress being laid on the 

 differences between the several groups, rather than 

 on the resemblances between the several animals 

 included in each individual group. An illustration 

 will perhaps serve to give a clearer idea of what is 

 meant. Take a piece of paper and make a number 

 of dots on it in a perfectly irregular manner. We 

 want to classify these dots, to arrange them in 

 groups : if we were to classify them by definition, 

 we should divide the paper by means of lines pass- 

 ing between the dots into a number of compartments 

 of convenient size, to which we should give distinc- 



