M 



Chap. XXVII. OF PANGENESIS. 397 



variability. Secondly, in the cases in which the organisation 

 has been modified by changed conditions, the increased use or 

 disuse of parts, or any other cause, the gemmules cast off from 

 the modified units of the body will be themselves modified, and 

 when sufficiently multiplied, will be developed into new and 

 changed structures. 



Turning now to Inheritance ; if we suppose a homogeneous 

 gelatinous protozoon to vary and assume a reddish colour, a 

 minute separated atom would naturally, as it grew to full size 

 retain the same colour; and we should have the simplest form 

 of inheritance. 53 Precisely the same view may be extended to 

 the infinitely numerous and diversified units of which the whole 

 body in one of the higher animals is composed; and the 

 separated atoms are our gemmules. We have already suffi- 

 ciently discussed the inheritance of the direct effects of chano-ed 

 conditions, and of increased use or disuse of parts, and, by im- 

 plication, the important principle of inheritance at corresponding- 

 ages. These groups of facts are to a large extent intelligible 

 on the hypothesis of pangenesis, and on no other hypothesis as 

 yet advanced. 



A few words must be added on the complete abortion or sup- 

 pression of organs. When a part becomes diminished by 

 disuse prolonged during many generations, the principle of 

 economy of growth, as previously explained, will tend to reduce 

 it still further ; but this will not account for the complete or 

 almost complete obliteration of, for instance, a minute papilla 

 of cellular tissue representing a pistil, or of a microscopically 

 minute nodule of bone representing a tooth. In certain cases 

 of suppression not yet completed, in which a rudiment occa- 

 sionally reappears through reversion, diffused gemmules derived 

 from this part must, according to our view, still exist; hence we 

 must suppose that the cells, in union with which the rudiment 

 was formerly developed, in these cases fail in their affinity for 

 such gemmules. But in the cases of complete and final abortion 

 the gemmules themselves no doubt have perished ; nor is this 



mS L^tnXho w T^f7 M t rie im elterlichen und 



(B ii s 17n who «««• ..fir, m kmdh( *™ Organismus, die Thei- 



uie prfelle M „«« y L sp el el ^ ^Tr V™ " *« *"*~ 



specmsch- zung, i S t die Ursache der Erblichkeit." 



