368 Ewart— Variation : Germinal and Environmental. 
Mr. Vernon is careful to pomt 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.” + 
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 immature 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. 
GERMINAL 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 environmental variations 
accumulated during the growth and maturation 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 echinoderms placed in chloride of magnesium, and then in sea-water, 
develop into larvee without being fertilized. ‘‘ Biology Lectures,” Woods Holl, Boston, 1899. 
+ Proceed. Roy. Soe., vol. Ixv., Nov., 1899. 
