CHAPTER IV. 



THE CLASSIFICATION OP ANOPHELES. 



; E shall attempt to consider this subject from the 

 points of view of the amateur naturalist and of 

 the worker on tropical diseases. When reviewing 

 a large number of animals or plants naturalists 

 divide them into groups which resemble one 

 another in different degrees. The largest group 

 or class includes many groups of orders. Each order includes subor- 

 dinate groups called families, and each family subordinate groups 

 called genera, under which again are grouped a number of species. 

 Finally each species includes a number of varieties. The foundation 

 of all these groups is laid in the groups of species, and in order to be 

 able to appreciate the value of any classification, it is necessary to 

 know exactly what is meant by this term. The word literally means 

 a look, an appearance, a kind ; beings which look the same are said to 

 be of the same species. In its natural history sense a species means 

 a group of individuals which closely resemble one another. A 

 species is subordinate to a genus a wider group of similar, but 

 less closely similar forms and is superior to a variety, of which 

 there may be several in a species. We may attempt to define the 

 limitations of the term " species " by the aid of examples. If, for 

 instance, we were to examine a number of children of the same 

 pair of parents we should note differences in their stature, 

 features, complexion, and in the colour of their hair and eyes, but 

 it is obvious that such differences which Darwin has termed 

 " individual differences" cannot be ranked as specific. The first 

 limitation of the term " species " must therefore be that individuals, 

 which are classed as belonging to different species, must present 

 greater differences than are exhibited between the offspring of any 

 single pair of parents. 



The second limitation would appear to be that the differential 

 characters of species must be constant from generation to generation. 



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