144 BLASTOGENIC VAEIATIONS. 



with anything more mysterious and remarkable than is 

 found in most of the phenomena of nature. Thus tak- 

 ing it for granted that each of the parts of an organism 

 capable of independent variation from the germ on- 

 wards has a definite representative or determinant of 

 some sort in the germ-plasm, what proportion does the 

 mass of the determinants of, say, all the characters 

 which distinguish a pouter or a fantail pigeon from a 

 rock pigeon, bear to the mass of the determinants which 

 represent the species pigeon, as such? Let us suppose 

 that the average total differences between the char- 

 acters of species of the same genus be counted as one 

 unit, what would be the number of units corresponding 

 to differences between the characters of genera, fam- 

 ilies, orders, and so on ? ~No two biologists would judge 

 alike, and of course it is impossible to estimate them; 

 but, for the sake of our argument, let us attempt some 

 sort of rough numerical estimate as to what these dif- 

 ferences might be. Let us assume that, if species on 

 an average differ bv one unit in the sum total of char- 



c/ 



acters, genera differ by three units, and families by per- 

 haps ten units. Orders might differ by 25 units, classes 

 by 50 units, and phyla by 100 units. Therefore we 

 assume that an individual of one phylum, in the sum 

 total of its characters, is 100 times more different from 

 an individual of another phylum than is one species 

 from another of the same genus. The difference be- 

 tween the highest Vertebrate and the lowest Protophyte 

 would probably be considered to be perhaps ten times 

 greater than this, but let that pass. Let us take it that 

 the sum total of characters represented by any species of 

 pigeon is 100 units, of which the total characters pe- 



