CHANGES IN GERM-CELLS 189 



to a poisoning of the embryo before birth, in a manner comparable 

 to pre-natal infection. 



(3) In some cases — e.g. of alcoholism in successive generations- 

 there may be poisoning of the germ-cells along with the 

 body, there may be poisoning of the embryo before birth, 

 and of the infant after ; but it may also be that what is really 

 inherited is a specific degeneracy of nature, an innate deficiency 

 of control, perhaps, which led the parent to alcoholism, and 

 which may find the same or some other expression in the child. 



Cases are known in which the children of a dipsomaniac father 

 and a quite normal mother have exhibited a tendency to 

 alcoholism, insanity, and the like. In this case the possibility of 

 poisoning the unborn child is eliminated, but there remain three 

 possibilities of interpretation, — that there was specific poisoning 

 of the paternal germ-cells ; that what was inherited was the 

 constitutional weakness which expressed itself as alcoholism 

 in the father ; and that there were detrimental influences in the 

 early nutrition, environment, education — " nurture," in short 

 — of the offspring. 



But while we have admitted a good deal, we have not admitted 

 the transmissibility of a particular structural modification brought 

 about in the parental body as a result of the toxin. 



An illustration of what we mean by the distinction " along with, 

 but not through the body," is afforded by an experiment of Paul 

 Bert's. He tried to acclimatise some Daphnia; (small fresh-water 

 crustaceans) to salt water by gradually adding salt to the aquarium. 

 At the end of forty-five days, when the water contained 1*5% of 

 salt, all the adults had died ; but the eggs in their brood-chambers 

 Burvived, and the new generation arising from these flourished well 

 in the salt medium {pit. Packard, 1894, p. 345). Packard sees 

 in this case an argument for the heritability of a modification, but 

 it seems to us merely an instance of the direct modification of 

 the germ-cells or of the embryos. Cuenot, whom Packard cites, 

 gives the correct interpretation : " This experiment shows with 

 admirable clearness that the germ-plasm has, owing to the modifi- 



