348 PRESENT PROBLEMS IN EVOLUTION AND HEREDITY. 



Applying these vit^vs to variation there should theoretically ap- 

 pear to be just those two distinct classes of anomalies in the human 

 body which we have seen actually occurring: First, those in the path 

 of evolution, arising from perfectly normal changes in the somato-plasm 

 and germ-plasm: second, those wholly unconnected with the course 

 of evolution, arising fortuitously or from abnormal changes in the 

 somato-plasm or germ plasm; to this head may be attributed the whole 

 scale of deformities. Thus tranformism and deformism should be 

 kept distinct in our minds. Nevertheless the facts of deformism con- 

 tribute the strong(ist body of evidence which we can nuister at i^resent 

 to prove that there does exist a relation between the somatoplasm and 

 germ-plasm which renders transformism possible. 



The relations hetireen the mmato-plamt and (lerm-plami . — We have 

 seen reasons to take a middle ground as to the distinct speciiic nature 

 of the body cells and germ cells, aiid thispositi<m is, I think, strength- 

 ened the more broadly we extend our inquiry into all the fields of pro- 

 toplasmic activity. 



There are three questions before us. 



1. What is the evidence that the germ-})lasm and somato-plasm are 

 distinct! 



2. What is the specific nature of the germ-plasm? 



3. What is the nature of the relations which exist between the two? 



1. The separation of the germ-jdasm is in the regular order of evolu- 

 tion upon the princijdes of physiological division of labor. The unicel- 

 lular organisms combine all the functions of life in a single massofpro- 

 toidasm, that is, in one cell. In the rise of the multi-cellular organisms 

 the various functions are distributed into groups of cells, which spe- 

 cialize in the perfecting of a single function. Thus the reproductive 

 cells fall into the natural order of histogenesis, and the theory of their 

 entire separation is more consistent with the laws governing the other 

 tissues than the theory which we find ourselves obliged to adopt, that 

 while separate they are still united by some unknown threads with the 

 other cells. 



The morphological separation of what we may call the race ])roto- 

 jilasm becomes more and more sharply defined in the ascending scale 

 of organisms. Weismann's contention as to the absolutely distinct 

 specific nature of the germ-plasm and sonmto plasm has however to 

 meet the apparently insuperable difficulty that in many multi-cellular 

 organisms, even of a high order, the potential capacity of repeating 

 com]dex hereditary characters, and even of producing perfect germ 

 cells, is widely distributed through the tissues. 



For example, cuttings from the leaves of the well-known hot-house 

 plant, the begonia, or portions of the stems of the common willow tree, 

 are capable of reproducing complete new individuals. This would in- 

 dicate either that portions of the germ plasm are distributed througii 

 the tissus of these organisms, or that each body cell has retained its 

 potential quota of hereditary characters. 



