The first principles of heredity; with 75 illustrations and diagrms . imitive germ-cells. for the upbuilding of an organism. The body, therefore,being incapable of producing the germ-cells anew, thereremains the only other possibility of deriving the germ-ceUs for the production of the next generation directlyfrom the germ-cells of the parents. Indeed, in some, though rare, cases such direct relation- 6o THE FIRST PRINCIPLES OF HEREDITY ship between germ and germ can clearly be traced. Thus,among the Diptera the first segmentation divides the ripeovum into two cells, of which one is the mother
The first principles of heredity; with 75 illustrations and diagrms . imitive germ-cells. for the upbuilding of an organism. The body, therefore,being incapable of producing the germ-cells anew, thereremains the only other possibility of deriving the germ-ceUs for the production of the next generation directlyfrom the germ-cells of the parents. Indeed, in some, though rare, cases such direct relation- 6o THE FIRST PRINCIPLES OF HEREDITY ship between germ and germ can clearly be traced. Thus,among the Diptera the first segmentation divides the ripeovum into two cells, of which one is the mother-cell of thefuture body, while the other is the mother-cell of the germ-cells of the new individual to be formed. In the embryo-genesis of the water-fleas [Daphnides] the primitive germ-cells are separated from the body-cells ( somatic cells)during the early stages of segmentation, while in theSagitta-^oxvci this differentiation of the germ-cells takesplace somewhat later still during the gastrula stage. Inthese latter cases the germ-plasm of the next generation is. B
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1910
