82 SECTIONAL” ADDRESSES. 
factor or set of factors under definite well-controlled conditions.’ You 
will remember that if a tissue substance, blood-serum for instance, of 
one animal be injected into the circulation of another, this second 
individual will tend to react by producing an anti-body in its blood to 
antagonise or neutralise the effect of the foreign serum. Now 
Professor Guyer’s ingenious experiments and results may be briefly 
summarised as follows. By repeatedly injecting a fowl with the sub- 
stance of the lens of the eye of a rabbit he obtained anti-lens serum. 
On injecting this ‘ sensitised’ serum into a pregnant female rabbit it 
was found that, while the mother’s eyes remained apparentiy 
unaffected, some of her offspring developed defective lenses. The 
defects varied from a slight abnormality to almost complete disappear- 
ance. No defects appeared in untreated controls, no defects appeared 
with non-sensitised sera. On breeding the defective offspring for 
many generations these defects were found to be inherited, even to 
tend to increase and to appear more often. When a defective rabbit 
is crossed with a normal one the defect seems to behave as a Mendelian 
recessive character, the first generation having normal eyes and the 
defect reappearing in the second. Further, Professor Guyer claims to 
have shown that the defect may be inherited through the male as well 
as the female parent, and is not due to the direct transmission of anti- 
lens from mother to embryo in utero. 
If these remarkable results are verified, it is clear that an environ- 
mental stimulus, the anti-lens substance, will have been proved to 
affect not only the development of the lens in the embryo, but also the 
corresponding factors in the germ-cells of that embryo; and that it 
causes, by originating some destructive process, a lasting transmissible 
effect giving rise to a heritable mutation. 
Professor Guyer, however, goes farther, and argues that, since a 
rabbit can also produce anti-lens when injected with lens substance, and 
since individual animals can even produce anti-bodies when treated 
with their own tissues, therefore the products of the tissues of an 
individual may permanently affect the factors carried by its own germi- 
cells. | Moreover he asks, pointing to the well-known stimulative 
action of internal secretions (hormones and the like), if destructive 
bodies can be produced, why not constructive bodies also? And so he 
would have us adopt a sort of modern version of Darwin’s theory of 
Pangenesis, and a Lamarckian view of evolutionary change. 
But surely there is a wide difference between such a poisonous or 
destructive action as he describes and any constructive process. The 
latter must entail, as I tried to show above, the drawing of new sub- 
stances into the metabolic vortex. Internal secretions are themselves 
but characters, products (perhaps of the nature of ferments) behaving 
as environmental conditions, not as self-propagating factors, moulding 
the responses, but not permanently altering the fundamental structure 
and composition of the factors of inheritance. 
Moreover, the early fossil vertebrates had, in fact, lenses neither 
larger nor smaller on the ayerage than those of the present day. If 
7 American Naturalist, vol. lv. 1921 ; Jour. of Leper. Zoology, vol. xxxi. 1920. 
