WHAT IS THE ORIGIN OF SPECIES? 189 



species) Logani Hall.* Taking Miller's "American Paleozoic 

 Fossils, "f we count this as species 115, and variety 2. 



Thus, to express it symbolically, we should have the 

 formula for the characters developed in this single particular 

 species ='B 6+ C2 + O4+F4 + Gio + Sii5+V2; 

 and all of this is implied in the common scientific name for the 

 species, Spirifer Logani Hall. 



This expresses the morphological characters of the species 

 arranged in the order of their respective ranks. 



New Species Conceived of as Arising by a Process of Variable 

 Characters becoming Permanent. Thus it is seen that there 

 are various degrees of mutability of the characters expressed 

 by any particular specific individual. The accounting for the 

 repetition of the characters already known in the ancestors 

 is by the natural laws of generation. In the example before 

 us the characters represented by the symbols (B 6), (C 2), etc., 

 to (S 115) are supposed to be relatively fixed characters so 

 far as transmission by generation is concerned, but the 

 characters represented by (V 2) are distinctly mutable in 

 generation, the descendants expressing them with varying 

 degrees of modification from their ancestors. These varietal 

 characters in the course of successive generations either (a) 

 drop out by degrees, (b) do not reappear at all, or (c) con- 

 tinue to reappear in the offspring In case they continue to 

 appear in the offspring, then they become added to the more 

 permanent specific characters, and when so added, in place of 

 (S 1 15 -f- V 2) we have (S 1 16), or a new species, all the other 

 characters remaining the same. Species (S 116) may be sup- 

 posed to show further variation, and (S n6-|-V3) and 

 (S ii6-|-V4) appear, and assume the same relations of 

 repetition by generation, forming species (S 117), (S 118), 

 etc.; but after a time the species (S 116), (S 117), (S 118), 

 (S 119) become dominant. (S 115), (S 114) drop out, and we 

 have a new genus (G 1 1), composed of the newly arisen 

 species (S 1 16), (S 117), (S 1 18), and (S 1 19), the constancy of 

 what was once a specific character becoming more fixed, and 



* " Geol. Survey of Iowa," vol. i. pt. 2, " Paleontology," by James Hall, p. 

 647, Plate XXI. 



t3dEd., p. 374 



