368 EwART — Variation : Germinal and Environmental. 



Mr. Vernon Is careful to point out — (1) that his results "prove the inequality of 

 the sex-cells, stale ova and fresh sperms giving very different results from fresh 

 ova and stale sperms, which implies that it is more important to have fresh ova 

 than fresh sperms,* unless intercrossing is aimed at, when fresh sperms seem to be 

 essential " ; and (2) that staleness may be a very potent cause of variation, " the 

 relative degree of freshness of ovum and spermatozoon at the time of fertilization 

 being in many cases entirely a matter of chance."t 



In the case of the spermatozoon, three phases may also be recognised — (1) a 

 fairly long period (when changes in the nutrition, &c., may account for much), 

 which ends with the formation of the second spermatocytes ; (2) the period 

 including the division of the spermatocytes to form spermatids — equivalent to the 

 reducing division stage in ova — and the growth of the spermatids into sperma- 

 tozoa ; and (3) the period between the completion of the spermatozoon and its 

 union (conjugation) with an ovum — a period which may extend over months or 

 even years. Even although the spermatozoa are, as a rule, extremely minute, it 

 has been possible to observe that their nuclei differ in their staining-reaction from 

 the corresponding egg-nuclei, and also that the nuclei of immatm-e sperms stain 

 differently from the nuclei of mature sperms. Further, observation may possibly 

 show that the sperms formed at the beginning of the period of reproduction differ 

 in staining-reaction from those formed when the climax is reached, as well as from 

 those formed during senescence, and that in domestic mammals (dogs, horses, &c., 

 at stud) the sperms produced at the beginning of the breeding season differ consi- 

 derably not only in their staining-reaction, but also chemically from those formed 

 towards the end of the breeding season. 



GEEMINAL VARIATION. 



By germinal variation I mean the variation that results from the union or 

 conjugation of the germ-cells. As already stated, the germ-cells up to the 

 moment of union are liable to be influenced by external stimuli, to undergo 

 environmental variation. During conjugation, as the nucleus of the male germ- 

 cell blends with its equivalent, the "reduced" nucleus of the female germ-cell, 

 all the variations inherited, as well as the potential envii-onmental variations 

 accumulated during the growth and matm-ation of the germ-cells, have an 

 opportunity of asserting themselves, that they are never all embodied in the new 



* According to Loeb, the ova of eoliinoderms placed in chloride of magnesium, and then in sea- water, 

 develop into larv£B without being fertilized. " Biology Lectures," Woods HoU, Boston, 1899. 

 f Proceed. Hoy. Soc, vol. Ixv., Nov., 1899. 



