236 Professor W. Bateson [Feb. 15, 



WEEKLY EVENING MEETING, 



Friday, February 15, 11)18. 



The Right Hon. Lord Raylei&h, O.M. D.C.L. LL.D. F.R.8., 



in the Chair. 



Professor W. Batesox, D.Sc. F.R.S. 

 Gamete and Zygote. 



[Absteact]. 



In modern biology the ideas denoted by the terms Gamete and 

 Zygote are fundamental No one having fnlly appreciated the 

 meaning of these ideas can look on the living Avorld with quite the 

 same eyes as before. The two expressions, Gamete and Zygote, were 

 introduced, in the haphazard fashion too commonly followed by 

 scientific men, to denote on the one hand the single, unpaired germs 

 or germ-cells, and on the other the double or paired bodies which 

 result from the union of two germ-cells in fertilization. The bodies 

 of most animals and plants are zygotes^ being the product of two 

 gametes or " marrying " cells " yoked " together in a common system, 

 the body. Except for differences in mobility and in the amount of 

 food materials w^hich they contain, there is so far as we know no 

 general or essential distinction between the germ-cells contributed 

 by the male and the female respectively. In the union of two such 

 cells, the powers, bodily and mental, of the resulting organism are 

 conveyed to it. By many competent observers it is believed that all 

 these powers are conferred solely by the nuclear materials of the 

 germ-cells ; and from certain elaborate and valuable experiments 

 Morgan and his associates have convinced themselves that the 

 properties of organisms are determined by particles of nuclear 

 material arjanged in a predicable linear order. Nevertheless alternative 

 hypotheses have not hitherto been adequately investigated. The 

 evidence most favourable to the chromosome scheme of heredity is 

 that furnished by the phenomenon called " non-disjunction '* by 

 Bridges. Here unusual zygotic types were consistently produced in 

 association with the visible presence of definite aberrations in the 

 chromosome numbers. Striking as this evidence is, it must still be 

 possible to doubt whether the relations are certainly those of cause 

 and effect. 



The different qualities being introduced on fertilization, the 

 problem of heredity is to discover the metliod and system by which 

 these differences are segregated and distril)uted among the gametes 



