534 SUMMARY OF CURRENT RESEARCHES RELATING TO 



In interpreting germinal variation, the author agrees in the main 

 with Weismann, and accepts the idea of germinal selection. 



The combined results of germinal and environmental variation are 

 then illustrated by giving the results of a number of inter- crossing and 

 inter-breeding experiments, which are of great interest and value. 



The following are some of the more striking results of inter- 

 crossing : — 



(1) The offspring may, down to the remotest details, be all but 

 intermediate between tbe two parents, but this is not very common. 



(2) The offspring often resembles one of the parents — the pre- 

 potent one. 



(3) Somo of the offspring may resemble one of the parents, some 

 the other. Thus, in a litter of four kittens, two may be pure white like 

 the sire, and two tabby like the mother. 



(4) The offspring may combine, almost unimpaired, the nvre striking 

 characters of both breeds. Though the engrafting of the characters of 

 one breed on another may not be common, it certainly occurs. 



(5) Sometimes new, or at least unexpected, characters appear in the 

 offspring, e.g. a grey tailless rabbit, "spinning" rabbits, reddish-brown 

 or chestnut rooks. 



(6) The offspring of half-breeds are, as a rule, extremely variable — 

 a fact long recognised by breeders, fanciers, and horticulturists. 



(7) Sometimes the offspring, instead of resembling the immediate 

 ancestors, i.e. the parents, resemble former ancestors. 



We have not been able to do more than outline the plan of a very 

 interesting paper, full of concrete detail of gieat value. 



Determination of Sex in Animal Development.* — J. Beard has 

 been led by certain discoveries to a theory of the determination of sex. 

 Enumerations showed him that the primary germ-cells of Raja batis 

 approximated to 256 or 512 ; "from evidences to be given elsewhere, it 

 was established that the larger number of primary germ-cells related to 

 the future female embryos, the smaller to potential males ; " it was found 

 that during the cleavage there are germinal discs of two sizes. 



Beard suggests that the " sterilised metazoau person " which we call 

 a female produces two kinds of functional gametes, viz. eggs which may 

 develop into males, and eggs which may develop into females. Similarly, 

 the male typically bears two forms of spermatozoa, one of which is 

 never of functional value, and may be never more than initiated. In 

 more than three dozen species two kinds of sperms are known. 



Since it is the egg that develops, and not the sperm, the burden of 

 providing for the continuance of the race is borne by the female 

 metazoou, or rather, by the germ-cells of which it is the host. They 

 make provision not only for a new batch of " female-eggs," but also for 

 one of "male-eggs." " The determination of sex for the next generation 

 thus lies with the germ-cells of the female metazoan organism," 



In all d cecious Metazoa there are thus three kinds of functional 

 gametes, two in the female, one in the male. '• The faculty of becoming 

 hermaphrcdite is confined to the female." From " male-eggs " she is 

 able on occasion, by anticipation, to form spermatozoa. Hermaphroditism 



* Anat. Anzeig., xx. (1902) pp. 556-G1. 



