No. 637] 



IMMUNE SERA 



105 



through a series of cell-divisions and specializations of 

 the new cells thus produced. During development cer- 

 tain cells are set apart, often very early in embryogeny, 

 for reproducing the next generation. Thus the gemi- 

 cells and the body-cells of a given organism develop at 

 the same time and neither is the product of the other ; 

 each alike has originated by division from the fertilized 

 ovum. There is no necessity, therefore, for collecting 

 samples from all parts of the body and concentrating 

 them in germ-cells, as Danvin supposed was done, for 

 the samples are already there, derived from the same 

 supply that produced the parental body. They exist not 

 in the form of such parts of an organism as are visible 

 to us, but simply as certain ingredients which when com- 

 bined in certain ways and developed in certain directions 

 give rise to the parts in question. Sooner or later the 

 body dies, but in the meantime one or more of the germ- 

 cells have passed on to become expressed as new bodies 

 and new germs. Thus a child does not inherit its char- 

 acteristics from corresponding characters in the parent- 

 body, but parent and child are alike because they are 

 products of the same fundamental materials. 



How, indeed, can a change in a brain-cell or a muscle- 

 cell find expression in a germ which is itself a cell that 

 possesses neither brain nor muscle? How can an influ- 

 ence at a distant part of the body even reach a germ-cell! 

 How can immature young, even larvae in some instances, 

 produce young which ultimately come to manifest the 

 characteristics of the adults of the species? How can 

 recessive Mendelian unit-characters disappear, perhaps 

 for generations, to reappear at last apparently with 

 qualities undimmed? How, on the Lamarckian basis of 

 use-inheritance, can the highly specialized characters of 

 the worker-bee have originated and become perfected 

 when the individual itself is sterile? How account for 

 adaptive characters based on passivity, or for mutual 

 adaptations such as may exist between plants and certain 

 animals? 'These and a host of questions like them con- 



