923 
of Edinburgh, Session 1885-86. 
the other hand, when the female parent is older than the male, 
when the female is at its physiological prime, when the ova fertilised 
are young and fresh, when food is abundant and environment 
favourable, the chances are distinctly in favour of the offspring 
being female. A few well-known cases may he briefly referred to. 
Thus old branches of conifers, overgrown and shaded by younger 
ones, produce only male inflorescences, and some fern prothallia in 
unfavourable conditions can still produce antheridia, hut not arche- 
gonia. Male plants of hazel grow more actively in heat than the 
female, and Stratiotes aloides hears only female flowers north of 52° 
lat., and from 50° southwards only male ones. Caterpillars starved 
before entering the chrysalis state produce males, while others of the 
same brood highly nourished come out females. In his well-known 
tadpole experiments, Yung raised the percentages of females in 
one brood from 56 in those unfed, to 78 in those fed with beef, and 
in another from 61 to 81 per cent, by feeding with fish; while, 
when the especially nutritious flesh of frogs was supplied, the per- 
centage rose from 54 to 92. 
Now such conditions as deficient or abnormal food, high tempera- 
ture, deficient light, moisture, and the like, are obviously such as 
would tend to induce a preponderance of waste over repair, — a 
Tcatabolic diathesis, — and we have just seen that these conditions 
tend to result in the production of males. Similarly, the second set 
of factors, such as abundant and rich nutrition, abundant light and 
moisture, must be allowed to be such as favour constructive pro- 
cesses, and make for anabolism, and we have just seen that these 
conditions result in the production of females. The explanation 
has thus been reached, that in the determination of sex, influences 
inducing katabolism tend to result in production of males, as those 
favouring anabolism similarly to increase the probability of females. 
B. Sex — Deductive Interpretation. — The theory may be confirmed, 
moreover, deductively as well as inductively, in proportion to the 
success of its interpretation of the various orders of phenomena, 
from the reproductive elements themselves to the sexual dimorphism 
of the entire organisms. Of this deductive rationale, however, 
only a few illustrative examples can here be given. 
(1) In regard to the reproductive elements, numerous empirical 
results, hitherto little more than curiosities of observation, admit 
