1892.] The Difficulties in the Heredity Theory. . 565 
germ-cell, as exhibited in the transmission of the characteris- 
tics of one sire to the offspring of a succeeding sire observed 
in animals, including the human species, also in plants. The 
best example is the oft-quoted case of Lord Morton’s mare, 
which reproduced in the foal of a pure Arab sire the zebra 
markings of a previous quagga sire. 
Some physiologists' have attempted to account for these 
remarkable indirect results from the previous fertilization or 
impregnation, by the imagination of the mother having been 
strongly affected or from interchange between the freely inter- 
communicating circulation of the embryo and mother, but the 
analogy from the action in plants (in which there is no gesta- 
tion but early detachment and development of the fertilized 
cells) strongly supports the belief that the proximity of male 
germ-cells acts directly upon the female cells in the ovary. 
All that we can deduce from these facts is that in some man- 
ner the normal characteristics and tendencies of the ova are 
modified by the foreign male ET without either contact 
or fertilization. 
Maternal Impression.—The influence of maternal impressions 
in the causation of definite anomalies in the fœtus is largely 
a matter of individual opinion. 
It is denied by some high authorities, led by Bergman and 
Leuckart? Most practitioners, however, believe in it, and I 
need hardly add that it is a universal popular belief? sup- 
ported by numerous cases. I myself am a firm believer in it, 
from evidence which I am not free to publish. The bearing 
which the subject has upon this discussion is this: if a devia- 
tion in the development of a child is produced by maternal 
impression we have a proof that a deviation from normal 
hereditary tendencies can be produced without either direct 
vascular or nervous continuity. 
e see an analogy between the experiments of Brown- 
Séquard, the influence of the previous sire, and the maternal 
1See the cases cited by Ribot and Darwin: Animals and Plants under Domestica- 
tion, vol. i, p. 437. 
2Handworterbuch der Physiologie, Wagner, Artikel “ Zeugung,” Leuckart. 
3See Medical Record, October 31, 1891, an article by Joseph Drzewiecki, M. D. 
