CONFORMITY TO TYPE 251 



entire part of the body consists; these, however, again depend on 

 the mode and rate of cell-division. 



"The processes occurring in the idioplasm which direct the 

 development of the organism from the ovum or, to speak in more 

 general terms, from one cell, the germ cell do not in themselves 

 furnish an explanation of a series of phenomena which are in part 

 directly connected with the autogeny, or else result from it sooner 

 or later; the phenomena of regeneration, gemmation, and fission, 

 and the formation of new germ cells, all require special supple- 

 mentary hypotheses. 



"The simplest cases of regeneration are due to the fully formed 

 tissue, consisting of similar cells} always containing a reserve of 

 young cells, which are capable of replacing a normal or abnormal 

 loss. This is, however, insufficient in the more complex cases, 

 in which entire parts of the body, such as the tail or limbs, are 

 regenerated when they have been forcibly removed. We must 

 here assume that the cells of the parts which are capable of 

 regeneration contain 'supplementary determinants' in addition 

 to those which control them, and that 'these are the primary 

 constituents of the parts which are formed anew in the process 

 of regeneration. They are supplied to certain parts of the body 

 at an earlier autogenetic stage in the form of 'inactive accessory 

 idioplasm/ and only become active when the opposition to growth 

 has been removed in consequence of the loss of the part in question. 

 The equipment of a cell of any part with supplementary determin- 

 ants presupposes a greater complexity in their distribution, in 

 correspondence with the greater complexity in structure of the 

 part; and thus the capacity for regeneration is limited, for a part 

 can no longer be provided with an apparatus for regeneration 

 when its structure is too complicated. The ordinary assumption 

 that the regenerative 'force' decreases as the complexity in 

 structure increases is therefore to a certain extent true, but not 

 if it implies the existence of a special force which provides for 

 regeneration and which always diminishes in correspondence 

 with the degree of organization. 



"Reproduction by fission is closely connected with regeneration; 

 it presupposes the existence of a similar apparatus in the idioplasm, 

 which, however, has in most cases reached a higher stage of 

 development : fission must have arisen phyletically from regener- 

 ation. 



" 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 Coelenterates 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 



