Cytology and Heredity 91 



but these mostly resolve themselves into improbable attempts to 

 expand or magnify the powers of Natural Selection. 



Weismann's interpellation, though negative in purpose, has had a 

 lasting and beneficial effect, for through his thorough demolition of 

 the old loose and distracting notions of inherited experience, the 

 ground has been cleared for the construction of a true knowledge of 

 heredity based on experimental fact. 



In another way he made a contribution of a more positive 

 character, for his elaborate speculations as to the genetic meaning of 

 cytological appearances have led to a minute investigation of the 

 visible phenomena occurring in those cell-divisions by which germ- 

 cells arise. Though the particular views he advocated have very 

 largely proved incompatible with the observed facts of heredity, yet we 

 must acknowledge that it was chiefly through the stimulus of Weis- 

 mann's ideas that those advances in cytology were made ; and though 

 the doctrine of the continuity of germ-plasm cannot be maintained 

 in the form originally propounded, it is in the main true and illu- 

 minating 1 . Nevertheless in the present state of knowledge we are 

 still as a rule quite unable to connect cytological appearances with 

 any genetic consequence and save in one respect (obviously of extreme 

 importance — to be spoken of later) the two sets of phenomena might, 

 for all we can see, be entirely distinct. 



I cannot avoid attaching importance to this want of connection 

 between the nuclear phenomena and the features of bodily organisa- 

 tion. All attempts to investigate Heredity by cytological means lie 

 under the disadvantage that it is the nuclear changes which can 

 alone be effectively observed. Important as they must surely be, 

 I have never been persuaded that the rest of the cell counts for 

 nothing. What we know of the behaviour and variability of chromo- 

 somes seems in my opinion quite incompatible with the belief that 

 they alone govern form, and are the sole agents responsible in 

 heredity 2 . 



1 It is interesting to see how nearly Butler was led by natural penetration, aud from 

 absolutely opposite conclusions, back to this underlying truth : " So that each ovum when 

 impregnate should be considered not as descended from its ancestors, but as being a 

 continuation of the personality of every ovum in the chain of its ancestry, which every 

 ovum it actually is quite as truly as the octogenarian is the same identity with the ovum 

 from which he has been developed. This process cannot stop short of the primordial cell, 

 which again will probably turn out to be but a brief restine-place. We therefore prove each 

 one of us to be actually the primordial cell which never died nor dies, but has differentiated 

 itself into the life of the world, all living beings whatever, being one with it and members 

 one of another," Life and Habit, 1878, p. 86. 



2 This view is no doubt contrary to the received opinion. I am however interested to 

 Bee it lately maintained by Driesch (Science and Philosophy of the Orga7iism, London, 1907, 

 p. 233), and from the recent observations of Godlewski it has received distinct experi- 

 mental support. 



