Inheritance Materials of Germ-Cells 75 



even though nothing were known as to exactly what goes 

 on in the germ while it is growing and ripening. But we 

 are by no means without positive knowledge under this 

 head. In fact the last few cell divisions immediately pre- 

 ceding the ripening of both ova and spermatozoa, and the 

 ripening processes themselves, have received searching ex- 

 amination during the last few decades, with the result that 

 hardly any cytological phenomena are better known than 

 are the profound morphological changes which accompany 

 these processes. That these changes are particularly mani- 

 fest in the chromosomes, the assumed seat of the determiners 

 of heredity, is one of the very things that has aroused so 

 much interest in the processes. Nor are we wholly unin- 

 formed about the chemical changes taking place in the 

 growing germ-cells. Unfortunately knowledge in this field 

 has hardly passed the stage of early infancy, but at least 

 enough is known to warrant the assertion that the young 

 germ-cells are subject, as are all the other cells, to the 

 general metabolism of the organism. 



Chemical Changes in Germ-Cells During Parent's Ontogeny 



About the most striking information we have in this 

 field is what has come from such investigations as those 

 on the chemical changes which occur in the sex glands and 

 other body parts during reproduction in some fishes.* Mie- 

 scher's work was ground-breaking in this domain for it 

 was the first to show that the "sexual organs in the salmon 

 develop at the expense of the muscular system, and that the 

 salmine deposited in the testis during the breeding season 

 must be derived from the proteins of the muscle, since the 



* Notable among these studies are: Histochemische und physiologische 

 Arbeit en, gescvnimelt und liermisgegeben von seinen Freunden, by Mie- 

 cher; and Changes in the Chemical Composition of the Herring during 

 the Reproduction Period, by Milroy. Biochemical Journ., v. in, 1908, p. 

 366. 



