^Ir. J. D. Dana on Sjyecies. 487 



condition, or law of force is an equivalent of every germ-cell in 

 the kingdoms of life. I do not mean to say that there is but 

 one kind of force; but that, whatever the kind or kinds, it has a 

 numerical value or law, although human arithmetic may never 

 give it expression. 



A species among living beings, then, as well as inorganic, is 

 based on a specific amount or condition of concentered force defined 

 in the act or law of creation. 



Any one species has its specific value or law offeree; another, 

 its value ; and so for all : and we perceive the fundamental no- 

 tion of the distinction between species when we view them from 

 this potential stand-point. The species, in any particular case, 

 began its existence when the first germ-cell or individual was 

 created; and if several germ-cells of equivalent force were cre- 

 ated, or several individuals, each was but a repetition of the 

 other : the species is in the potential nature of the individual^ 

 whether one or many individuals exist. 



Now in organic beings, — unlike the inorganic, — there is a 

 cycle of progress involving growth and decline. The oxygen 

 molecule may be eternal as far as anything in its nature goes. 

 But the germ-cell is only an incipient state in a cycle of changes, 

 and is not the same for two successive instants ; and this cycle 

 is such that it includes in its flow, a reproduction, after an inter- 

 val, of a precise equivalent of the parent germ-eell. Thus an 

 indefinite perpetuation of the germ-cell is in fact eflPected ; yet it 

 is not mere endless being, but like evolving like in an unlimited 

 round. Hence, when individuals multiply from generation to 

 generation, it is but a repetition of the primordial type-idea ; 

 and the true notion of the species is not in the resulting group, 

 but in the idea or potential element which is at the basis of every 

 individual of the group ; that is, the specific law of force, alike 

 in all, upon which the power of each as an existence and agent 

 in nature depends. Dr. Morton presented nearly the same idea 

 when he described a species as a primordial organic form. 



Having reached this idea as the starting-point in our notion 

 of a species, we must still, in order to complete and perfect our 

 view, consider what is the true expression of this potentiality. 

 For this purpose, we should have again in mind, that a living 

 cell, unlike an inorganic molecule, has only a historical existence. 

 The species is not the adult resultant of growth, nor the initial 

 germ-cell, nor its condition at any other point ; it comprises the 

 whole history of the development. Each species has its own 

 special mode of development as well as ultimate form or result, 

 its serial unfolding, inworking and outflowing ; so that the pre- 

 cise nature of the potentiality in each is expressed by the line of 

 historical progress from the germ to the full expansion of its 



