294 PROTOZOA 



such limitations and confusions is perhaps to be explained in part 

 by the aura which surrounds the word species and in part by the 

 justifiable satisfaction of having delimited a biological level of 

 organization of great evolutionary importance. Darwin forged a 

 close connection between the term species and evolution theory. 

 Everyone knows the term. To confiscate it for an objectively 

 defined evolutionary unit is tempting. In the process, certain 

 broader considerations were put aside. 



Classification into species preceded evolution theory and had 

 as its prime functions ordering and identification. It still has, and 

 for all kinds of organisms, not for outbreeders only. In spite of 

 the reproductive implications of the biblical account of creation, 

 with each kind of organism reproducing true to type, and in spite 

 of the early scientific usage of species as referring to the type- 

 maintaining original creations, it can hardly be denied that the 

 primary function of the word species was to designate a unit of 

 identification. This long usage has become deeply ingrained. 

 The universal need for it with respect to all organisms is recog- 

 nized by practically all biologists. However distasteful it may be 

 to some geneticists, there seems to be no possibility that biol- 

 ogists in general will ever agree to restrict the term species to 

 the carriers of a common pool of genes. 



Even the proponents of that concept of species would probably 

 agree with most of my statements in the immediately preceding 

 paragraphs. Dobzhansky ( 1941 ) himself makes most of these 

 points. He says that the systematists task must be primarily to 

 pigeon-hole, that the term species is used in more than one 

 sense by being applied both to taxonomic species and common 

 gene pools, that species are discrete by reason of complex ge- 

 netic differences, and so on. But he is willing to accept this 

 situation along with its logical inconsistency, terminological in- 

 consistency, and confusion. 



Only deep attachment to the word species seems to prevent 

 recognition that the needs of biologists would best be served by 

 having a separate term, such as syngen, for the unit of evolution 

 when it is known not to be the same as the unit of identification. 

 When the) are known to be the same, then they are at once both 



