238 BIOLOGY: GENERAL AND MEDICAL 



"The origin of multiplication by gemmation and the phenomena 

 exhibited by this form of reproduction are different from those 

 concerned in fission. In plants and Ccelenterates gemmation 

 originates in one cell, which must consequently contain a com- 

 bination of all the determinants of the species closely resembling 

 that existing in the fertilized ovum. In the Polyzoa, however, 

 this process does not originate in one cell, but in at least two, and 

 probably more, belonging to two different layers of cells (germinal 

 layers) of the body; and in Tunicata, again, the material for the 

 bud is produced from all three germinal layers. The first of these 

 forms of budding must be primarily due to the mixture of ' unalter- 

 able ' germ plasm to certain series of cells in autogeny in the form 

 of inactive 'accessory idioplasm/ or 'blastogenic' idioplasm. In 

 plants this is contained in the apical cells, and in the hydroid 

 polyps in the cells of the ectoderm. In the second group of 

 animals mentioned, we must assume that the 'blastogenic' germ- 

 plasm becomes disintegrated into two groups of determinants at 

 an early autogenetic stage and that each of these is passed on in an 

 1 unalterable ' condition, through various generations of cells, until 

 the time and place of its activity are reached. In the third group, 

 the inactive ' blastogenic ' idioplasm divides into three groups of 

 determinants, one of which passes into the ectoderm, the second 

 into certain cell series of the mesoderm, and the third into others 

 in the endoderm, until they reach the part in which they have 

 to become active. 



" Gemmation must have originated phyletically by a doubling of 

 the germ plasm taking place in the fertilized egg so that one 

 half remained inactive and was then passed on as inactive ' blasto- 

 genic' germ plasm, or else became divided up in the course of 

 autogeny into groups, which were passed separately to the same 

 region, viz., that of the bud. 



" We assume that two kinds of germ plasm exist in those species 

 in which alternation of generation occurs, both of which are present 

 in the egg cell as well as in the bud, though only one of them is 

 active at a time and controls autogeny while the other remains 

 inactive. The alternating activity of these two germ plasms 

 causes the alternation of generations. 



" The formation of germ cells is brought about by the occurrence 

 of similar processes in the idioplasm to those which cause gem- 

 mation. One part of the germ-plasm contained in the fertilized 

 egg cell remains inactive and 'unalterable'; that is, it does not 

 immediately become disintegrated into groups, but is passed on in 

 the form of accessory idioplasm to certain series of cells in autogeny, 

 and thus reaches the parts in which germ cells are to be formed. 

 Thus, the whole of the parental germ plasm, with all its determin- 

 ants, forms the foundation of the germ cells which give rise to the 

 next generation, and the extremely accurate and detailed trans- 

 mission of the parental characters to the offspring is thereby 

 rendered comprehensive. 



" In multicellular plants and animals, the germ plasm becomes 

 more complex in consequence of sexual reproduction, in which 

 process the ids of two different individuals, the parents, are 



