TRANSACTIONS OK SECTION II 759 



bulk of the body of the parent they can transmit to the offspring the characters of 

 the parent organism. Various speculations and theories have been advanced by 

 way of explanation. The well-known tlu'ory of Pan<renesis, which Charles Darwin 

 with characteristic moderation put forward as merely a provisional liy])Othesis, 

 assumes that gemmules are thrown oif from each dilVerent cell or unit throughout 

 the body which retain the characters of the cells from which they spring; that the 

 gemmules aggregate themselves either to form or to become included within the 

 reproductive cells; and that in this manner tliey and the characters which they 

 convey are capable of being transmitted in a dormant state to successive genera- 

 tions, and to reproduce in them the likeness of their parents, grandparents, and 

 still older ancestors. 



In 1872, and four years afterwards, in 187C, Mr. Francis Galton published most 

 suggestive pa])ers on Kinship and Heredity.' In the latter of these papers he 

 developed the idea that ' the sum total of the germs, gemmules, or whatever they 

 may be called,' which are to be found in the newly fertilised ovum, constitute a 

 atirp, or root. That the germs which make up the stirp consist of two groups — the 

 one which develops into the bodily structure of the individual, and wliich consti- 

 tutes, therefore, the personal structure ; the other, which remains latent in the 

 individual, and forms, as it were, an undeveloped residuum. Tliat it is from these 

 latent or residual germs that the sexual elements intended for producing the ne.xt 

 generation are derived, and that these gei-ms exerci.se a predominance in matters of 

 heredity. Further, that the cells which make up the personal structure of the 

 body of the individual exercise only in a very foint degree any influence on the 

 reproductive cells, so that any moditications acquired by the individual are barely, 

 if at all, inherited by the oHspring. 



Subsequent to the publication of Mr. Galton's essays, valuable contributions to 

 the subject of Heredity have been made by Professors Brook.'^, Jaeger, Naegeli, 

 Nnssbaum, Weismann, and others. Professor Weismanu's theory of Heredity em- 

 bodies the same fundamental idea as that propounded by Mr. CJalton ; but as he 

 has employed in its elucidation a phraseology which is more in harmony with that 

 generally used by biologists, it has had more immediate attention given to it. As 

 Weismann's es.?ays have, during the present year, been translated for and pub- 

 lished by the Clarendon Press,- under the editorial superintendence of Messrs 

 Poulton, Schonland, and Shipley, they are now readily accessible to all English 

 readers. 



Weismann asks the fundamental question, ' How is it that a single cell of the 

 body can contain within itself all the hereditary tendencies of the whole organ- 

 ism?' He at once discards the theory of pangenesis, and states that in his 

 belief the germ-cell, so far as its essential and characteristic sub,stance is concerned, 

 is not derived at all from the body of the individual in which it is produced, but 

 directly from the parent germ-cell from which the individual has also arisen. He 

 calls his theory the continuity of the (jerin-plnsm, and he bases it ui)on the supposi- 

 tion that in each individual a portion of the specitic germ-plasm derived from the 

 germ-cell of the parent is not used up in the construction of the body of that indi- 

 vidual, but is reserved unchanged for the formation of the germ-cells of the succeed- 

 ing generation. Thus, like Mr. Galton, he recognises that in the stirp or germ 

 there are two cla.sses of cells destined for entirely distinct purposes : the one for 

 the development of the soma or body of the individual, which class he calls the 

 somatic cells; the other for the perpetuation of the species, i.e., for reproduction. 



In further exposition of his theory Weismann goes on to say, a.s the pro- 

 cess of fertilisation is attended by a conjugation of the nuclei of the reproductive 

 cells— the pronuclei referred to in an earlier part of this address— that the nuclear 

 substance must be the sole bearer of hereditary tendencies. Each of the two 

 uniting nuclei would contain the germ-plasm of one parent, and this germ-plasm 

 also would contain that of the grandparents as well as that of all previous gene- 

 rations. 



• Proc. Jioij. Soc. Lond., 1872, and Joiirn. Anthrop. Jnst., vol. v., 1876. 

 ' Oxford, 1889. 



