CHAPTER 1.V.--EVOLUTION, 1870-1882.
LETTER 235. TO J. JENNER WEIR. Down, March 17th .
It is my decided opinion that you ought to send an account to some scientific society, and I think to the Royal Society. (235/1. Mr. Jenner Weir's case is given in "Animals and Plants," Edition II., Volume I., page 435, and does not appear to have been published elsewhere. The facts are briefly that a horse, the offspring of a mare of Lord Mostyn's, which had previously borne a foal by a quagga, showed a number of quagga-like characters, such as stripes, low-growing mane, and elongated hoofs. The passage in "Animals and Plants," to which he directs Mr. Weir's attention in reference to Carpenter's objection, is in Edition I., Volume I., page 405: "It is a most improbable hypothesis that the mere blood of one individual should affect the reproductive organs of another individual in such a manner as to modify the subsequent offspring. The analogy from the direct action of foreign pollen on the ovarium and seed-coats of the mother plant strongly supports the belief that the male element acts directly on the reproductive organs of the female, wonderful as is this action, and not through the intervention of the crossed embryo." For references to Mr. Galton's experiments on transfusion of blood, see Letter 273.) I would communicate it if you so decide. You might give as a preliminary reason the publication in the "Transactions" of the celebrated Morton case and the pig case by Mr. Giles. You might also allude to the evident physiological importance of such facts as bearing on the theory of generation. Whether it would be prudent to allude to despised pangenesis I cannot say, but I fully believe pangenesis will have its successful day. Pray ascertain carefully the colour of the dam and sire. See about duns in my book ["Animals and Plants"], Volume I., page 55. The extension of the mane and form of hoofs are grand new facts. Is the hair of your horse at all curly? for [an] observed case [is] given by me (Volume II., page 325) from Azara of correlation of forms of hoof with curly hairs. See also in my book (Volume I., page 55; Volume II., page 41) how exceedingly rare stripes are on the faces of horses in England. Give the age of your horse.
You are aware that Dr. Carpenter and others have tried to account for the effects of a first impregnation from the influence of the blood of the crossed embryo; but with physiologists who believe that the reproductive elements are actually formed by the reproductive glands, this view is inconsistent. Pray look at what I have said in "Domestic Animals" (Volume I., pages 402-5) against this doctrine. It seems to me more probable that the gemmules affect the ovaria alone. I remember formerly speculating, like you, on the assertion that wives grow like their husbands; but how impossible to eliminate effects of imitation and same habits of life, etc. Your letter has interested me profoundly.
P.S.--Since publishing I have heard of additional cases--a very good one in regard to Westphalian pigs crossed by English boar, and all subsequent offspring affected, given in "Illust. Landwirth-Zeitung," 1868, page 143.
I have shown that mules are often striped, though neither parent may be striped,--due to ancient reversion. Now, Fritz Muller writes to me from S. Brazil: "I have been assured, by persons who certainly never had heard of Lord Morton's mare, that mares which have borne hybrids to an ass are particularly liable to produce afterwards striped ass-colts." So a previous fertilisation apparently gives to the subsequent offspring a tendency to certain characters, as well as characters actually possessed by the first male.
In the reprint (not called a second edition) of my "Domestic Animals" I give a good additional case of subsequent progeny of hairless dog being hairy from effects of first impregnation.
P.S. 2nd. The suggestion, no doubt, is superfluous, but you ought, I think, to measure extension of mane beyond a line joining front or back of ears, and compare with horse. Also the measure (and give comparison with horse), length, breadth, and depth of hoofs.