406 HISTORY OF THEORIES 



particle, destined to give rise to a closely related cell. 

 Such a cell will be a hybrid, tending to vary. 



(7) As the ovarian ova of the offspring share, by direct in- 



heritance, all the properties of the fertilised ovum, the 

 organisms to which they give rise will tend to vary in 

 the same way. 



(8) A cell which has thus varied will continue to throw off 



gemmules, and thus to transmit variability to the corre- 

 sponding part in the bodies of successive generations of 

 descendants until a favourable variation is seized upon 

 by natural selection. 



(9) As the ovum which produced this selected organism will 



transmit the same variation to its ovarian ova by direct 

 inheritance, the characteristic will be established as 

 specific, and transmitted henceforth without gemmules. 

 The above theory, being important, has been stated at some 

 length. Apart from the suggestion of variation as due to sexual 

 intermingling, with which Weismann has made us more familiar 

 apart, too, from the suggestion of germinal continuity, the credit 

 of which Brooks shares there are several important points to 

 be emphasised in the modification proposed. It is in unwonted, 

 and, abnormal conditions that the cells of the body throw off 

 gemmules. The male elements are the special centres of their 

 accumulation ; the female it is that keeps up the general resem- 

 blance between offspring and parent. 



It is not proposed to enter into criticism of pangenetic theories. 

 The best criticism is found in that abandonment of special 

 hypotheses which more recent advances have rendered possible. 

 It has often been urged that the hypothesis of pangenesis involves 

 not one but many suppositions that it is just as difficult to 

 understand why a gemmule should reproduce a cell like its own 

 origin as to understand the entire problem, and so on. Detailed 

 criticism will be found in the works of Galton, Ribot, Brooks, 

 Herdman, Plarre, and others. It is enough for us to emphasise 



