AMERICAN ASSOCIATION FOR TfiE ADVANCEMENT OP SCIENCE. 79 



a measured quota or specific law of force. "We cannot apply the measure, as in 

 the inorganic kingdom, for we have learned no method or unit of comparison. 

 But it must nevertheless be true, that a specific predetermined amount^ or condi-' 

 tion, 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 specif e 

 amount or condition cf concentered force defined in the act or law of creation. 



Any one species has its specific value, or law of force ; another, its value ; and 

 so for all : and we perceive the fundamental notion 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 wag 

 created ; and if several germ-cells of equivalent force were created, 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 ia a cycle of progress in-» 

 Tolving growth and decline. The oxygen molecule may be eternal as far as any 

 thing in its nature goes. But the germ-cell is but 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 interval, of a precise equivalent 

 of the parent germ-celL Thus an indefinite perpetuation of the germ-cell is in 

 fact effected ; yet it is not mere endless being, but like evolving like in an un- 

 limited 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 spe- 

 cies 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.prim- 

 ordial organic form. 



Having reached this idea as the starting point in our notion of a species, we 

 niust 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 organic molecule, has only an 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 developement. 

 Each species has its own special mode of developement as well as ultimate form 

 or result, its serial unfolding, inworking and outflowing ; so that the precise nature 

 of the potentiality ia each is expressed by the line of historical progress from the 

 germ to the full expansion of its powers, and the realization of the end of its being. 

 "We comprehend the type-idea only when we understand the cycle of evolution 

 through all its laws of progress, both as regards the living structure under devel- 

 opement within, and its successive relations to the external world. 



2. Permanence of species. 



What now may we infer with regard to the permanence or fixedness of species 

 from a general survey of nature ? 



Let us turn again to the inorganic world. Do we there find oxygen blending by 

 Indefinite shadings with hydrogen or with any other element? Is its combining 



