664 ZOOLOGY SECT. 



would require that in such a case a large proportion of the 

 ordinary cells of the plant should receive gemmules derived from 

 all parts. 



It is a moot point whether it is possible that any influence 

 (such as is pre-supposed in pangenesis) can pass from the cells of 

 the various parts of the body to the ova whether there can be 

 any communication of substance carrying with it tendencies to be 

 transmitted to the next generation. It is certain, however, that 

 an influence of a centrifugal character is exerted by the sexual 

 cells. The absence of ovaries or testes has, in many cases, a 

 marked effect on certain of the characters an effect on the 

 development and form of certain of the parts. This is seen not 

 only in higher animals (Mammals and Birds), but also among 

 some lower forms. In certain Crabs, for example, the presence of 

 Sacculina, a parasitic Rhizocephalaii nourished at the expense of 

 the testes, which become destroyed, produces a very marked 

 alteration in some of the external features. But, while this is the 

 case, an influence exerted in the opposite direction an influence 

 transmitted from the other parts to the germ-cells, has not been 

 proved, and from the nature of the case perhaps cannot be 

 directly proved. Such an influence, it is hardly necessary to add, 

 must be pre-supposed if we assent to the doctrine of the in- 

 heritance of acquired characters. 



On this problem certain experiments which have been made on 

 the transplantation of ovaries promise to throw light. It has been 

 found possible to remove the ovaries in early stages from in- 

 dividuals of one variety of animal and to transplant them into 

 individuals of another variety without impairing the reproductive 

 functions. This has been done most successfully in the case of 

 certain breeds of Domestic Fowls. The ovaries of young hen-chicks 

 of two distinct breeds have been interchanged, and the effects on 

 the offspring investigated. The results which have been obtained 

 so far seem to place it beyond doubt that the eggs from the trans- 

 planted ovary do not develop exactly as they would had the 

 latter remained till maturity in the body of a Fowl of the variety 

 from which the ovary was originally taken : the progeny show 

 unmistakable traces of an influence exerted on them by the 

 individual, of a distinct variety, in which they were brought to 

 maturity : they present some of the features of their " mother by 

 transplantation." This seems to prove the possibility of the trans- 

 mission from the body or soma to the germ-cells, during their 

 growth, of influences of a definite character destined to bring 

 about definite effects on the offspring ; and this department of 

 research in experimental embryology would appear to promise to 

 show that there actually exists a mechanism such as the trans- 

 mission of acquired characters in normal heredity seems to 

 demand. 



