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'. 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’. - 
1 It is interesting to see how nearly Butler was led by natural penetration, and 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 resting-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. 
? This view is no doubt contrary to the received opinion. I am however interested to 
see it lately maintained by Driesch (Science and Philosophy of the Organism, London, 1907, 
p. 238), and from the recent observations of Godlewski it has received distinct experi- 
mental support. 
