214 SUMMARY OF CURRENT RESEARCHES RELATINQ TO 



that that layer also effects their transformation into the rudiments of 

 the permanent rays, and not the ei)iderm or embryonic integument, 

 as heretofore generally held by anatomists. The whole liistory of 

 the fin-folds, in fact, favours such a conclusion, since the horny fibres 

 develope between tlie corium and epidermis or embryonic skin, in the 

 plane of the protomorphic line of Huxley. The fin-folds of embryo 

 fishes, it should be borne in mind also, are at first wholly epidermic, 

 the corium or true skin being only developed during the later-larval 

 or i^ost-larval life. 



Origin of the Hypoblast in Pelagic Teleostean Ova.* — G. Brook, 

 on comparing notes with Dr. Whitman, finds that his conclusions are 

 completely at variance with those of that naturalist, and gives there- 

 fore a detailed accoimt of his own observations with careful drawings. 

 An inspection of these is needed for a complete comprehension of the 

 paper. 



Regulation of the Proportion of the Sexes in Man, Animals, 

 and Plants f — ^u the further elaborate essay of K. Diisiug he starts 

 from the fact that in animals, as in man, male and female individuals 

 always and everywhere stand to one another in quite definite numerical 

 relations ; in Homo sapiens the proportion is about 106 boys to 100 

 girls ; the former, however, are more frequently born dead, and a 

 larger number die in childhood. The consequence of this is that, at 

 the period of greatest reproductive activity the number of each sex is 

 about equal. Nearly similar results obtain with domesticated animals. 

 Nor is the constancy co ifined to animals, for Heyer has shown that a 

 definite relation of the sexes obtains in the dioecious plant Mercurialis 

 anmin. 



It is, however, well known that with small numbers very dif- 

 ferent results to those just enunciated are obtained ; in other words, 

 there is often a divergence from the norm. How is this corrected ? 

 Diising answers that an excess of one sex brings about a larger 

 number of births of the other. The author then discusses the 

 statistics of births, and especially of births after wars, an account of 

 which has already been given. f 



If Diising's doctrine that nutriment has influence on the sex be 

 correct, it is clear that animals with similar nutrition must be gene- 

 rally of the same sex ; and this is true, wo know, of twins and double 

 abortions. 



The author next investigates the effects of dissimilar nutritions, 

 and commences with a study of human statistics. With bad nourish- 

 ment a boy, with good a girl is developed ; in the country there are 

 more boys born than in towns, for the townspeople are, on the whole, 

 better nourished. Parents in good condition have fewer boys than 

 the poor. The age of the mother is also of importance ; young 

 females feed better than old, and have more girls. Where bodily 

 exercise is considerable, as among the inhabitants of young countries, 



* Quart. Journ. Micr. Sci., xxv. (1885) pp 29-37 (1 pi.). 



t Jenai«'h. Zeit-chr. f. N^tiirwiss:.. xvii. (1884) pp. 593-940. 



j Set this Juuriia), iv. (1884) [>. 708. 



