ON HEKKDITY. 543 



these germ or reproductive cells become influenced, sotbat aftei liaviug 

 been isolated from the cells \Ybich make up the bu-lk of the body of the 

 parent they can transmit to thi^ offspring the characters of the parent 

 organism. Various speculations and theories have been advanced by 

 the way of explanation. The well known theory of Pangenesis, which 

 Charles Darwin with characteristic moderation put forward as merely a 

 provisional hypothesis, assumes that gemmules are thrown off from each 

 different cell or unit throughout the body which retain the characters of 

 the cells from which they spring; that the genunules aggregate them- 

 selves either to form or to become included within the reproductive 

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

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

 sive generations, and to reproduce in them the likeness of their parents, 

 grand[)arents, and still older ancestors. 



In 1872, and four years afterwards, in 1870, Mr. Francis Galton pub- 

 lished most suggestive pai)ers on kinship and heredity.* In the latter 

 of these papers he developed the idea that '' the sum total of the 

 germs, gemmules, or whate\'er the\' nmy be called," which are to be 

 found in the newly fertilized ovum, constitute a stirj), or root. That 

 the germs which make up the stirp consist of two groups; the one 

 which develo[)s into the bodily structure of the individual, and which 

 constitutes therefore tiie i)ersonal structure; the other, wiiich remains 

 latent in the individual, and forms, as it were, an undeveloped residuum 

 That it is from these latent or residual germs that the sexual elements 

 intended for producing the next generation are derived, and that these 

 germs exercise a liredominauce in matters of heredity. Further, that 

 the cells which make up the personal structure of the body of the in- 

 ilividual, exercise ouly in a very faint de.uree any influence on the repro- 

 ductive cells, so that auy modifications ac<]uired by the individuals are 

 barely, if at all, inherited by the offspring. 



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

 tributions to the subject of heredity have been made by Professors 

 Brooks, Naegeli, Nussbaum, Weismann, and others. Professor Weis- 

 manu's theory of heredity embodies the same fundamental idea as that 

 propounded by Mr. Galton ; 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 Weis- 

 mann's essays have during the present year been translated for, and 

 published by the Clarendon Press,f under the editorial sui)erintendence 

 of Messrs. Poulton, Schonlaud, and Shi{)ley, tiiey are now readily ac- 

 cessil)le to all English readers. 



Weismann asks the fuinlamental (juestion, " How is it that a single 

 cell of the body can contain within itself all the hereditary tendencies 

 of the whole organism ?•' He at once discards the theory of pangenesis, 



* Proceedings Roy. Soc. Lond., 1S72, uiid Jouni. Anthrop. Inst., 187(5, vol v. 

 t Oxford, 18HU. 



