Heredity and the Origin of Variations. 141 



developed, and the ovum from which the daughter is 

 developed, are simply two fragments separated at different 

 times from the same continuous germ-plasm.* Both 

 develop under similar circumstances, and their products 

 cannot, therefore, fail to be similar. How variation is 

 possible under these conditions we shall have to consider 

 presently. 



Now, although I value highly Professor Weismann's 



n, 



Fig. 21. Egg and hen. 



/. " The egg produces the hen." //. " The hen produces the egg." In 7. the dints pro- 

 duced by the environment are not inherited t in //. they are. The letters indicate successive 

 individuals. The small round circles indicate the egga. 



luminous researches, and read with interest his ingenious 

 speculations, I cannot but regard his doctrine of the con- 

 tinuity of germ-plasm as a distinctly retrograde step. His 

 germ-plasm is an unknowable, invisible, hypothetical entity. 

 Material though it be, it is of no more practical value than 

 a mysterious and mythical germinal principle. By a little 

 skilful manipulation, it may be made to account for any- 



* It will, of course, be understood that a minute fragment of germ-plasm 

 is capable of almost unlimited growth by assimilation of nutritive material, 

 its properties remaining unchanged during such growth. 



