558 SCIENCE PROGRESS 



for example, the germ cells and the somatic cells can be dis- 

 placed artificially and each will carry on the work of the other. 

 Even when this is no longer possible, the somatic cells cling 

 tenaciously to their ancient privilege and only give it up 

 little by little. 



Direct Reproduction from Germ Cells 



The germ cells are concerned solely with reproduction. 

 Their mission in life is to form and give off the buds that will 

 grow into living organisms for the next generation. At first 

 there is no suggestion of such a thing as sex. How and when 

 it first came about that germs to reproduce the race, instead 

 of growing from a single cell, should require a stimulus coming 

 from a second one to start them on their course, is not known ; 

 but it is obvious that germs formed in this way, by the fusion 

 of parts of two cells, would stand a better chance of success 

 in the struggle for existence than those formed from a single 

 cell, if only because of the greater likelihood of the occurrence 

 of useful variations. When this bi-cellular origin was once 

 initiated, the division of the primitive germ organ into two 

 parts, an ovary and a testis, each providing its own special 

 factor in reproduction ; the maturing of the two products at 

 different times, so that the conjunction of two separate indi- 

 viduals would be required, and the comparative weakness of 

 self-fertilisation avoided ; and then the suppression of one 

 of these organs in one of the individuals and of the other in 

 the other, with the result of separating the sexes entirely, 

 are such obvious advantages that they follow as a matter of 

 course. 



Sexual reproduction, therefore, which bulks so largely in 

 our vision that it has caused the existence of the primitive 

 method of direct reproduction to be almost ignored, is only a 

 specialisation. The primitive method, the birthright of all 

 living tissues, continues to exist in the background. It does 

 not die out or disappear because the sexual organs have been 

 developed. It is still there, though its range of action grows 

 more and more limited, and if occasion requires can be called 

 into play at once. In many insects, for example, generations 

 in all respects identical with those that precede them can be 

 produced asexually, even though functional sexual organs 



