Cook: The Existence of Species 



157 



tion. Organisms maintain their exist- 

 ence and make evolutionary progress 

 only in species. It is the species, rather 

 than the individual, that has a truly 

 biological existence. Evolution and 

 heredity are collective, superorganic pro- 

 cesses, hardly to be understood from the 

 standpoint of the individual organism. 

 Instead of disregarding species, students 

 of general biological problems should 

 consider the association of all plants and 

 animals in species, in other words, the 

 speciety of living matter, as one of the 

 most significant and fundamental facts. 

 That this condition or property of 

 speciety is not analogous to any of the 

 physical and chemical properties of 

 unorganized matter, should give it a 

 special interest for the biological inves- 

 tigator.- 



The traditional analogy of the genea- 

 logical tree also gives a misleading idea 

 of the nature of organic succession. The 

 usual object of a genealogical tree is to 

 show descent from a single ancestor, and 

 unless consanguineous marriages occur, 

 all the branching lines of descent remain 

 separate and distinct. But this apparent 

 distinctness is maintained only because 

 each marriage is a grafting with a 

 branch of a different family tree. If all 

 these genealogical trees with their inter- 

 grafted branches could be represented, 

 we would have a diagram corresponding 

 to the network of descent of the species. 



That the network of descent is lacking 

 in definite form or external morpho- 

 logical structure is not a reason for deny- 

 ing that the species has organization, 

 for amoebae and many other living 

 organisms lack definite form. This is 

 true even of some highly specialized 

 organs, such as the brain, whose func- 

 tions are not at all dependent upon 

 regularity of external form. Morpho- 

 logical specialization is, after all, only a 

 secondary result of protoplasmic special- 

 ization. The conditions that determine 

 protoplasmic efficiency must be recog- 

 nized before we can hope to understand 

 organization in the external, structural 

 sense. 



Some have thought to gain a better 

 understanding of heredity by analyzing 



the diversified natural species into uni- 

 form pure lines, where the analogies of 

 the physical sciences more nearly apply. 

 Yet evolution is not an analytic process, 

 but highly synthetic. The specific 

 organization of interweaving lines of 

 descent provides for the accumulation 

 and combination of the desirable varia- 

 tions, those that render the species better 

 adapted to its environment. To un- 

 ravel the network of descent into sepa- 

 rate lines may help us to understand 

 some of the problems of heredity, but 

 it does not represent the essential con- 

 dition of normal, self -perpetuating or- 

 ganic existence, or of evolutionary 

 progress. None of the analytic experi- 

 ments in the propagation of single lines 

 of descent are permanently sticcessful. 

 If the crossing of the lines of descent is 

 prevented, as by vegetative propagation 

 or by artificial breeding, the individual 

 structures become abnormal or weak and 

 eventually cease altogether. Our vege- 

 tative varieties and pure bred strains 

 are short-lived. None of the higher 

 types of plant or animal life are main- 

 tained without sexual reproduction in a 

 specific network of descent. 



THE NETWORK OF DESCENT. 



To say that the power of organization 

 is lodged in the individual germ cell 

 is not the whole biological truth. The 

 power resides rather in the specific 

 organization, the protoplasmic network 

 of the species, of which the individual 

 germ is but a fragment. The vitality 

 of the individual depends upon its 

 relation to the organization of the 

 species. The specific networks of des- 

 cent, rather than the individual lines, 

 have the power to develop and main- 

 tain the complex structures of the 

 higher animals and plants. Organiza- 

 tion in this sense of complex cellular 

 structures is not a general property of 

 protoplasm, for it is not manifested by 

 the lowest forms of life, but is rather to 

 be considered as an accomplishment of 

 the higher forms, those that have de- 

 veloped complex specific organizations 

 and correspondingly specialized sexual 



2Cook, O. F. 

 1912. 



Physical Analogies of Biological Processes. The American Naturahst, 46: 493, 



