HEREDITY 455 



the lack of equilibrium between the organization and 

 its environment, which embraces that proposition 

 without definite specification. To Weismann we are 

 indebted for the exposition of the separate origin and 

 relative isolation of the germ-plasma, but no sufficient 

 explanation of the origin and inheritance of new char- 

 acters is offered. Ryder 1 has especially dwelt on the 

 physiological division of labor seen in the tissues of 

 the organism, and on the special function of the germ- 

 plasma as the recipient of impressions through the 

 processes of metabolism ; but he does not go into 

 greater detail. 



What is true of the somatic cells is also true of 

 those which follow immediately the segmentation of 

 the oosperm. Each division contains the entire record, 

 until a point is reached in which specialization of its 

 growth-capacities begins. 



Dr. Chalmers Mitchell thus discusses the question 

 as to the location of specialized growth in the oosperm : 2 



" Loeb uses the term heteromorphosis to denote 

 the power of organisms, under the stimulus of outer 

 conditions, to produce organs on parts of the organism 

 where they do not occur normally, or the power to re- 

 place lost parts by parts unsimilar to them. Regenera- 

 tion is the reproduction of like parts. Heteromorpho- 

 sis is the reproduction of unlike parts. 



"It one cuts off part of the stem of almost any 

 plant, on placing the stem in suitable soil, roots will 

 grow out, although roots are not natural to that part 

 of the stem. The prothallus of fern produces the male 

 and female organs on the lower side turned away from 

 the light. If the prothallus be darkened on the upper 



1 Aii-riian Naturalist^ 1890, p. 85. 

 % Natural Science ) 1894, p. 187. 



