1881.] OF THE INDIVIDUAL AND OF THK SPECIES. 469 



forces resulting in the production of a new creature resembling its 

 immediate and more remote progenitors, in varying degrees, according 

 to (I) the amount of force springing from each ancestral strain, and 

 (2) the compatibility or incompatibility ' of the prevailing tendencies — 

 resulting in an intensification, perpetuation, modification, or neutra- 

 lization of ancestral characters, as the case may be. 



All such action is but " heredity " acting in one or other mode ; but 

 there is another, and fundamentally different, action which has to be 

 considered, and that is the action of the environment upon nascent 

 organisms — an action exercised either directly upon them, or indirectly 

 upon them through its direct action upon their parents. That such 

 actions produce unmistakable effects is notorious. It will be, I 

 think, sufficient here to advert to such cases as the well-known 

 brood-mare covered by a quagga, and the ])eculiar effects of a well- 

 bred bitch being lined by a mongrel. These show how an action 

 exercised upon the female parent (hut with no direct action on the 

 immediate offspring) may act indirectly upon her subsequent pro- 

 geny. 



As a rule, modifications accidentally or artificially induced in 

 parents are not transmitted to their offspring ; as is well shown by 

 the need of the repetition of circumcision, and of pressure of Indian 

 children's heads and Chinese girls' feet in each generation. Yet there 

 is good evidence that such changes are occasionally inherited. The 

 epileptic offspring of injured Guinea-pigs is a case often referred to. 

 Hackel speaks of a Bull which had lost its tail by accident and which 

 begot entirely tailless calves. With respect to Cats" I am indebted 

 to Mr. John Birkett for the knowledge of an instance in which a 

 female with an injured tail produced some stump-tailed kittens in 

 two litters. 



There is evidence tliat certain variations are more apt to be 

 inherited than others. Amongst those very apt to be inherited are 

 skin affections, affections of the nervous system and of the generative 

 organs, e. g. hypospadias and absence of the uterus. The last case 

 is one especially interesting, because it can only be propagated 

 indirectly. 



Changes in the environment notoriously produce changes in 

 certain cases even in adults. The modifications which may result 

 from the action of unusual agencies on the embryo have been well 

 shown by M. C. Dareste^. As has been already remarked, processes 

 of repair take jolace the more readily the younger the age of the 

 subject. Similarly it is probable that the action of the environment 

 generally acts more promptly and intensely on the embryo than in 

 the older young. That the same organism will sometimes assume 



' Mr. Darwin tells us that two topknotted Canaries produce bald oifspi'ing, 

 due ])robably to some conflicting actions analogous to the interference of light. 



2 See ' The Oat ' (John Murray, 1881), p. 7- 



^ See ' Archives de Zool. expcr.' vol. ii. p. 414, vol. v. p. 174, vol. vi. p. 31. 

 also Ann. des Sci. Kat. 4 scries, Zoologie, vol. iii. p. 1 19, vol. xv. p. I, vol. xvii. 

 p. 243 ; and his work ' Eecherches sur la production artilicielle des Monstru- 

 osites ou essais de Teratogenie experimentale.' 



Pkoc. Zool. Soc — 1884, No. XXXII. 32 



