400 SECTIONAL TRANSACTIONS.—D. 
14. Mr. J. T. CunnineHam.—Lamarckism and Secondary Sexual 
Characters. 
It has Jong been known that in vertebrates, especially in mammals, the 
secondary characters of the male do not develop normally after castration. It 
has been proved that the connecting link between the development of these 
characters and the gonads consists of the internal secretions or hormones of the 
latter organs, circulating in the blood and lymph. 
The structural sexual characters, as distinct from colour, are the result of 
local hypertrophy of the kind which would be produced by the irritations and 
stimulations caused in the sexual behaviour of the animals, such as fighting, 
courtship, or holding the female. The neo-Lamarckian theory proposed by me 
to explain the evolution of these characters is that the hypertrophy or excessive 
growth repeated in each generation ultimately became hereditary, but was only 
developed by heredity in the presence of the hormones from the gonad which 
was present when it was originally produced. This theory thus affords an 
explanation of the influence of the hormones of the gonads on the development 
of somatic sexual] characters, whereas no other theory throws any light on this 
influence, since the characters in question are not in themselves essentially sexual 
or reproductive, and may occur in almost any part of the body, or may be 
entirely absent. 
The influence of the hormones from the gonads in birds has been found to 
be different from their influence in mammals. ‘The male plumage in ducks, 
fowls, and pheasants is not suppressed by castration of the male bird, but on 
the other hand removal of the ovary in the hen is followed by. development 
of the male plumage. The absence of male plumage in the normal hen is 
therefore due to its suppression by the ovarian hormone. The explanation of 
this is discussed in the paper. Even more remarkable is the fact that in hen- 
feathered breeds of poultry castration of the male results in the development of 
the male plumage which is normally absent. 
The absence of any effect on somatic sexual characters after castration in 
moths and the subject of parasitic castration in Crustacea are briefly considered 
in the paper. 
15. Prof. D. M.S. Watson, F.R.S.—Pal@ontology and Mendelism. 
16. Dr. E. H. Cratcie.—Changes in Vascularity in the Brain between 
Birth and Maturity. 
Quantitative measurements of the vascularity of fourteen selected regions in the 
brain stem and the cerebellum of the albino rat at different ages reveal the facts 
that the brain is much less richly supplied with blood vessels at birth than in later 
life, and that there is relatively little difference in the capillary supply of the different 
centres at this age. 
The vascularity changes little during the first five days, but increases somewhat 
in most regions by the tenth day. Between the tenth and the twenty-first days there 
is a rapid proliferation of capillaries, so that the vascularity in all but one of the 
centres studied in the brain stem reaches a maximum apparently about the latter 
age. The sensory centres, moreover, become in general richer than the motor ones, 
the relations being similar on the whole to those in the adult. 
The cerebellar centres, however, do not reach their maximum vascularity until 
the one-hundred-and-forty-days-old stage, at which time the capillary supply of the 
chief vestibular nucleus is also at its richest. 
After the maximum vascularity has been reached, there is a gradual decrease in 
capillary richness. 
It is evident that the richness of the vascular supply is related more to the require- 
ments for functional activity than to those for growth. 
17. Prof. J. W. Mavor.—The Effect of X-rays wpon the Transmission 
of Mendelian Characters. 
Afternoon Excursion on Lake Ontario. 
