may 1899] TELEGONY, XENIA, AND " HYBRID OOLOGY" 393 



Should we consider that there is sufficient reason for supposing 

 that telegony does sometimes occur, and is an occasional factor in 

 heredity, we must then turn our attention to its cause, as it might 

 prove of the greatest importance to any theory explanatory of this 

 subject. 



I think the explanation of the phenomenon given by Romanes x 

 is the most satisfactory, for that given by the supporters of Pan- 

 genesis, and other like theories, postulates such an extraordinary activity 

 and plasticity on the part of the spermatozoa and their contained 

 gemmules. After reaching the ovaries too late for the fertilisation 

 of the mature ovum they must be supposed to penetrate the walls of 

 the generative organs and fuse with the somatic cells. Then these 

 cells must cast off gemmules which by some means or other must 

 reach and form part of the succeeding and yet immature ova. 



The provisional explanation suggested by Weismann, — that the 

 spermatozoa might penetrate the succeeding ova while yet immature, 

 has two objections to it, — first, the improbability of the efficiency of 

 the spermatozoon to penetrate the follicular coverings of an immature 

 ovum ; and secondly, the objection mentioned by Weismann himself, 

 that " a supplementary fertilisation of an egg-cell in this manner must 

 be considered possible. . . . But this has never been known to 

 occur." 2 The two explanations mentioned by Darwin 3 may be passed 

 over with the barest mention, the one of the intercommunicating 

 blood vessels between the embryo and mother, because it does not 

 hold good in the case of birds, and from Mr. W. Heape's splendid 

 experiments 4 does not affect mammals ; and that of imagination be- 

 cause " there are very slight grounds for any such belief." 5 



As far as I know, the suggestion of Romanes has never been dis- 

 cussed since. It appears the simplest theory, and is one which, instead 

 of showing telegony in the light of an objection to the Weismannian 

 (or, in fact, any other) theory, is in perfect harmony with it. 



Xenia. 



This, the direct action of the male element on the mother-plant, is 

 an extremely hypothetical theory, the only facts on which it is based 

 being those mentioned by Darwin. De Vries 7 and Focke s have both 

 expresssed their doubts as to its occurrence, and until fresh experi- 



1 Viz. "that the life of 'ids' is not commensurate with that of their containing 

 spermatozoa. . . . And . . . when subsequent ova mature . . . these dormant ids adhere 

 to their porous walls, through which they may pass." — Op. eit. p. 198. 



2 A. Weismann, "The Germ-Plasm," p. 386. 



3 C. Darwin, " Variation under Domestication," vol. i. p. 437. 



4 See Nature, December 30, 1897, in which is a report of Mr. Heape's paper (published 

 by the Royal Society) on the " Transplantation and growth of mammalian ova in a uterine 

 foster-mother." 5 C. Darwin, "Variation under Domestication," vol. i. p. 437. 



6 Op. <■;/. p. 427 ct seq. 7 II. de Vries, " Intracellular!' Pangenesis," p. '206. 



8 Focke, "Die Pflanzcn-Mischlinge," p. 500 ct seq. 



