372 Thoughts on Species. 



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generation, it is but a repetition of tlje primordial type-idea • 

 and tlie true notion of tlie sj^ecies 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 startiiig 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 Kne 

 of historical progress from the germ to the full expansion of its 

 powers, and the realization of the end of its being. We com- 

 prehend the type-idea only when we understand the cycle of 

 evolution through all its laws of progress, both as regards the 

 living structure under development 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 number, its potential 

 equivalent, a varying number, — usually 8, but at times 8 and a 

 fraction, 9, and so on ? Far from this the number is as fixed as 

 the universe. There are no indefinite blendings of elements. 

 There are combinations by multiples or submultiples, but these 

 prove the dominance and fixedness of the combining numbers. 



But further than this, even numbers, definite in value and de- 

 fiant of all destroying powers, are well known to characterize 

 nature from, its basement to its top-stone. We find them in 

 combinations by volume as well as weight, that is in all the re- 

 lations of chemical attraction ; in the mathematical forms of 

 crystals and the simple ratios in their modifications, — evidence 



