THE BIOLOGICAL EVIDENCE 83 



prematurely (i.e. some time before ovulation is due) fertilized by a 

 buck of different strain, the young take after the sire ; when the 

 fertilization takes place at the usual time, some of the young 

 resemble the buck, some the doe, while some present new 

 characters, or reproduce, more or less accurately, one or more of 

 the ancestors. When, however, the mating is delayed about thirty 

 hours beyond the normal time, all the young, as a rule, resemble 

 the doe. It may be inferred that in mammals, as in echinoderms, 

 the characters of the offspring are related to the conditions of the 

 germ-cells at the moment of conjugation, the offspring resulting 

 from the union of equally ripe germ-cells differing from the offspring 

 developed from the conjugation of ripe and unripe germ-cells, and 

 still more from the union of over-ripe germ cells." 1 



134. A species of butterfly is bright coloured in Germany, but 

 of a darker hue in Italy. Weismann reared the Italian variety in 

 a low and the German in a high temperature. The former became 

 lighter, but not so light as the German variety ; the latter became 

 darker, but not so dark as the Italian type. Like Professor Ewart, 

 he does not appear to have ascertained whether the alterations 

 were reproduced by subsequent generations. 2 Hoffman sowed wild 

 plants very thickly in pots. After several generations they 

 produced double flowers never observed before. Pictet altered 

 the colour of butterflies by transferring the caterpillars from the 

 normal food plant to another. He found that each kind of abnormal 

 food impressed characteristic effects on offspring. These effects 

 persisted and increased for some generations, but eventually the 

 race became adapted to the new food, and thereupon returned to 

 the primitive type. 3 " Dr Bachman states that he has seen turkeys 

 raised from the eggs of the wild species lose their metallic tints and 

 become spotted with white in the third generation." 4 Mr Hewitt 

 " found he could not breed wild ducks true for more than five or six 

 generations, as they proved so much less beautiful. The white 

 colour round the neck of the mallard became broader and more 

 irregular, and white feathers appeared in the ducklings' wings." 5 

 Metzger cultivated in Europe a tall variety of maize brought from the 

 warmer parts of America. " During the first year the parents 

 were twelve feet high, and a few seeds were perfected ; ... in the 

 second generation the plants were from nine to ten feet in height 

 and ripened their seeds better. . . . Some of the seeds had even 



1 Loc. cit., p. 482. 2 The Germ-plasm, p. 389. 



3 L' Influence de V Alimentation et de I'Humidite sur la Variation des Papillons. 



4 Animals and Plants, vol. ii. p. 250. 5 Op. cit. y vol. i. p. 340. 



