202 THE PHILOSOPHY OF BIOLOGY 



degree of stability so that the individuals " breed 

 true to type " ; and it has also attained a high degree 

 of specialisation, so that it does not fuse with other 

 organisations. 



Yet, in the marjoity of the systematic species of 

 biology, this criterion of specific individuality — this 

 recognition of the isolation of the species from other 

 species — cannot be applied. Very many species have 

 been described from a few specimens only, many from 

 only one. How does a systematist recognise that an 

 organism with which he is dealing has not already been 

 classified ? It differs from all other organisms most 

 like it, that is, he cannot identify it with any known 

 specific description. But the differences may be very 

 small, and if he had a number of specimens of the 

 species most nearly resembling it he might find that 

 these differences were less than the limits of variation 

 in this most closely allied species, and he would then 

 relegate it to this category. But if he has to compare 

 his specimen with the " type ' one, that is, the only 

 existing specimen on which the species of comparison 

 was founded, the test would be unavailable. The 

 question to be answered is this : are the difference 

 or differences to be regarded as fluctuations, or are 

 they of " specific rank " ? Now certainly many 

 systematists of great experience possess this power 

 of judgment, though they might be embarrassed by 

 having to state clearly what were the grounds on which 

 their judgment was based. But on the other hand 

 hosts of species have been made by workers who 

 did not possess this quality of judgment ; and even 

 with the great systematists of biology confusion has 

 originated. Slowly, very slowly, the organic world 

 is becoming better known, and this confusion is 

 disappearing. 



