Finally let me add, not another argument, but another fact of observation, of the kind which opponents demand, but which, when they are from time to time furnished, are severally pooh-poohed as not enough. Each of them is spoken of as a solitary fact and slighted as inadequate; and when by and by another is named, this is treated in the same way; so that the facts which if brought together would be recognized as sufficient are never brought together. That to which I refer is set forth in a pamphlet by M. Leo Errera, Professor at the University of Brussels, entitled “Hérédite d’un Caractère acquis chez un Champignon pluricellulaire;” being an account of experiments of Dr. Hunger, at the Botanical Institute in Brussels. First enumerating various instances of adaptations to climate, as those of plants which, fitted to northern regions, preserve their constitutional rapidity of growth and seeding when brought south, and do this for several generations, he goes on to detail the culture-experiments of M. Hunger, and sums up the results of these in the following words:—

“On déduit de là que:

“1o Les conidies d’Aspergillus niger sont adaptées à la concentration du milieu où a vécu l’individu qui les porte; cet effet est encore plus marqué après deux générations passées dans un milieu donné (Expér. I et II);

“2o II s’agit d’une véritable adaptation et non pas simplement d’un accroissement de vigueur chez les conidies provenant des liquides concentrés, car ces mêmes conidies germent moins rapidement et donnent des plantes moins vigoureuses que les conidies normales lorsqu’on les sème de nouveau sur le milieu-type: en s’adaptant aux liquides concentrés, elles se sont désadaptées du liquide normal (Expér. III);

“3o Une génération passée sur le liquide normal n’efface pas l’influence d’une ou de deux générations antérieures passées sur une liquide plus concentré (Expér. IV).

“Tous ces résultats concordent: ils montrent une légère, mais incontestable transmission héréditaire de l’adaptation au milieu.”

SUBJECT-INDEX.

(For this Index as it appeared in previous editions the Author is indebted to F. Howard Collins, Esq., of Edgbaston, Birmingham. It has now been adjusted to suit the present revised and enlarged edition.)