16 CALIFORNIA ACADEMY OF SCIENCES. 



plasma he asserted to be the vital formative principle of 

 every cell, what remained being merely nutritive. The 

 general term somatoplasm was then of course abandoned. 

 There are, then, according to this theory, two series 

 throughout the body, one formative, the other reproduc- 

 tive. The formative, which is the chromatin of the nu- 

 cleus, passes under the general term of idioplasma. 

 When present in the germ-cells it is called germ-plasm; 

 in the body cells," somatic idioplasm." The nutritive sub- 

 stance is what was previously known as somatoplasm. 

 To it also a new term was given, " cytoplasma." Hav- 

 ing made these distinctions, Weismann explains his idea 

 of embryogenesis. This takes place, according to his 

 theory, by the successive halvings of the nuclear loops 

 or germ-plasm. "Each fresh cell-division," he says, 

 " sorts out tendencies which were mixed in the nucleus 

 of the mother-cell, until the complex mass of embryonic 

 cells is formed, each with a nuclear idioplasma which 

 stamps its specific histological character on the cell." A 

 minute part of the idioplasm he assumes to remain un- 

 changed when the first transformation occurs, in order 

 to preserve the continuity of the germ-plasm. This 

 fragment of germ-plasm migrates in an inactive condi- 

 tion from cell to cell, until it comes to the spot where it 

 develops into the germinal cells of the next generation. 

 How, then, does the controversy between Prof. Vines 

 and Prof. Weismann rest? Briefly, Prof. Vines has 

 shown that Weismann has not accounted for the intro- 

 duction of mortality in the order of life, although it is 

 upon the assumption of such a differentiation of cells 

 into mortal and immortal that his entire theory rests. 

 Vines has not shown, however, that such a differentia- 

 tion is impossible. Weismann, on the other hand, has 

 refuted the charge of the inconsistency of assuming that 

 germ-plasm can be converted into somatoplasm, although 



