MENDEL*S LAWS OF HEREDITY IN INSECTS. l43 



which the writer described an aberration of this species, which he 

 names lacticolur'- , and gave an account of his efforts to breed it. The 

 aberration is apparently confined to the female sex, and when a 

 specimen was mated with a normal (iroH>ndariata not a single lact i color 

 appeared among the offspring. When, however, some of the latter 

 were paired together, among their progeny a consideral)le number of 

 lacticolor appeared. Some of these were then paired with normal 

 male (p-ossitlariata, presumably of diiferent stock, and again no 

 lacticolor appeared. When the paper was written not enough insects 

 had hatched to draw any conclusions from the results of the pairings 

 among this last lot, but probably lacticolor will again come up among 

 them. 



At first sight this seems very remarkable, that among the children 

 of a lacticolor there should be none resembling their mother, but that 

 the aberration should appear again in some abundance in the grand- 

 children. But the results are so exactly in accord with what would 

 be expected according to the Mendelian law of heredity, that it has 

 seemed to me worth while to draw attention to the facts. In a simple 

 Mendelian case, when two varieties — in this instance tirossidariata and 

 lacticolor — are bred together, their offspring all resemble one of the 

 parents, and the character of that parent is said to be " dominant," . 

 while the character of the other parent, which disappears in the first 

 generation of offspring, is called "recessive." But although the 

 recessive character disappears, it is latent, and the hybrid offspring 

 produce germ-cells bearing either the dominant character or the reces- 

 sive, but not both charactei's, in the same germ-cell. If, now, equal 

 numbers of dominant [(jrossidariata) and recessive {lacticolor) germ- 

 cells are produced by each hybrid, and these meet one another in 

 fertilisation quite by chance, then, according to the law of probability, 

 the insects of the second generation should be in the proportion of 

 IDD, 2DK, IRR, DD representing an insect derived from an ovum 

 and spermatozoon each bearing the dominant character, RR from two 

 germ-cells bearing the recessive character, and DR from germ-cells, 

 one of which bore the dominant, the other the recessive, but, in 

 every case where a dominant-bearing germ-cell has taken part in 

 fertilisation, the offspring will show the dominant character, so that, 

 in the second generation from the cross, one quarter only of the insects 

 should appear with the recessive {lacticolor) character. Of the 

 remaining three-quarters, all of which will be yroaaulariata, two-thirds 

 will be hybrid in nature, and will give recessive lacticolor when bred 

 together, while the remainder will be pure tjroi<s.idariata, and will never 

 throw lacticolor when bred together. This particular instance is com- 

 plicated by the fact that lacticolor is confined to the female, and, there- 

 fore, if a specimen is paired with a pure (jroasidariata, no lacticolor will 

 appear in the offspring ; but it should be possible to breed lacticolor 

 in every generation by pairing it with a dominant hybrid (J3R) which 

 has the ijroKsidariata character in appearance, but also the recessive 

 lacticolor character in a latent condition. Mr. Raynor does not tell 

 us what proportion of his insects were lacticolor in the second genera- 

 tion from the cross, but this is a matter of considerable interest, for 



* Mr. Prout has since shown (Entovi. Record, xv., p. 109) that this particular 

 aberration should be called flavofasciata, Huene. 



