HEREDITY IN PLANTS, ANIMALS, AND MAN. 399 
and can be seen for himself by anyone who will take the trouble to carry 
out the necessary experimental work, taking all precautions to prevent 
false crossings by insects or false matings. 
Mendel himself experimented also on a number of other characters in 
peas, and found that they followed the same scheme. Tall plants were 
dominant to dwarfs, and when the first tall hybrids were self-fertilised 
they gave tall and dwarf plants in the proportion of 3:1. Coloured 
flowers were dominant to white, but the whites reappeared again in the 
next generation. 
In order to explain his results Mendel put forward a simple theory, the 
correctness of which all subsequent work has tended to confirm. Before 
attempting to explain this theory I must ask you to regard plants and 
animals from a point of view somewhat different from that which we 
usually take—from the point of view of the race or species rather than 
from that of the individual life. The plant withers, the flower fades, the 
creature dies, but still the race continues, 
“So careful of the type she seems, 
So careless of the single life.” 
How is this continuity of the race preserved ? That is the fundamental 
question which the physiology of heredity must seek to answer. What 
we know is that the germ cell, the germ plasm as Weismann called it, 
passes on uninterruptedly from generation to generation, creasing In 
bulk by the absorption of nourishment, dividing and subdividing, but 
apparently only seldom or extremely slowly undergoing any essential 
modification of its structure. The permanent, essential feature for the 
species is this germ plasm ; the body of the individual plant or animal is an 
elaborate but purely temporary home for its protection and nourishment. 
As Samuel Butler puts it in his quaint way “a hen is merely an egg’s 
way of producing another egg.” 
ce Ss 
is Immortal; the excrescence, the body, is 
“The germ plasm, according to this 
view, says Darbishire 
mortal.” 
It is in the gametes or germ cells—the ovule and the pollen of the plant 
and the corresponding structures of the animal—that the germ plasm is 
carried on. In the higher plants and animals this transmission is gener- 
ally, though not always, complicated by the introduction of the pheno- 
menon of sex, the union of the germ cells from two individuals of the 
species, or at least of germ cells of two different kinds. 
In formulating his theory to account for the scheme of the hereditary 
transmission of characters which has been described, Mendel directed his 
attention primarily to the germ cells. HKvery gamete, that is to say every 
ovule and every grain of pollen, must contain something by means of 
