354 EwART — Variation : Germinal and Environmental. 



that have in due course appeared, an extreme latter-day preformationist might, 

 at least, be willing to admit that it contained '* germs " of the coming organisms. 

 But there is no more evidence that protoplasm was originally endowed with the 

 innate power of varying, irrespective of external stimuli, than that in the ovum 

 of a bird or a mammal there lies concealed a fully formed and complete 

 miniature of the adult. At the present day biologists (whether they are simple 

 followers of Darwin, and are tinged with Lamarckism, or whether with Weismann 

 they refuse to subscribe to the doctrine of the transmission of acquired characters) 

 are nearly all agreed that variation has been mainly due, directly or indirectly, to 

 the cumulative influence of external forces, such as food, light, heat, moisture, 

 and the action of organisms on each other — in a word, to the influence of the 

 environment. 



For some years the question has not so much been "is protojjlasm suscejitible 

 to external stimuli?" as "was the susceptibility lost when the metazoa stage in 

 the phylogeny was reached, i.e. have variations in the metazoa been mainly due 

 to stimuli influencing ages ago their protozoon ancestors?" Have the Vertebrates, 

 and the other metazoa for countless ages been simply ringing the changes on 

 variations accumulated by their remote simple unicellular progenitors ? Professor 

 Weismann, who (by his "ids" and "determinants") reminds one of the less 

 extreme " preformationists," would probably still give an affirmative answer to 

 this question, even though he believes that the germ-plasm "consists, to a great 

 extent, of specific ids " and of only a few ancestral ones.* 



Hitherto students of evolution have generally discussed variation under two 

 heads, viz. : — congenital variations and acquired variations. But, as in the case 

 of mammals, certain congenital variations are really acquired and not necessarily 

 transmitted, and as some variations which might very well be looked upon as 

 acquired {e.g. variations due to differences in age and vigour, and to ripeness of 

 germ-cells) are transmitted, I propose speaking of variations as Germinal and 

 Environmental. 



The most critical and momentous period in the life-history of any plant or 

 animal is during the conjugation of the male and female germ-cells. 



During conjugation (fertilization), as the germ-cells more or less completely 

 blend with each other, and as new combinations, partly chemical and partly 

 mechanical, are rapidly formed, the fate of the new individual is largely fixed. It is 

 not so much that the conjugation causes variation, as that effect is given to 

 variations inherited from near and remote ancestors or accumulated during the 

 growth and maturation of the germ-cells. It is to this variation, which inevitably 

 flows from the blending of the two highly specialized germ-cells, I have given the 

 name Germinal Variation. During conjugation the minute details of the new 



* " The Germ-Plasm," p. 435. 



