Full text: Problems in eugenics

2Exhibit C 2—6. 
this change of colour appears in the same way in the offspring, 
though a direct influence of the colour of the earth on the germ plasm 
is absolutely unthinkable. The two pictures in the lower part of 
Figure C 1 show the colouring of that generation to which the animal 
portrayed above belongs, according as to whether they have been kept 
permanently on yellow soil (right) or returned again to black soil (left). 
Here, it is true, it is not a question of a new quality or tendency. 
The capacity in the parents to deposit black pigment in their 
skin has been increased or decreased according to their surroundings. 
But the distinctive point remains, that their offspring is subsequently 
endowed with the inherited tendency to produce proportionately more 
or less pigment. This may, however, be a direct result of the 
abnormal life conditions of the parents, in so far as the depositing 
of more or less pigment in the skin of the parents is certainly not 
a purely local process, but rather is bound up with other metabolic 
changes which may extend to or influence the developing gametes. 
C 3 & 4 Very remarkable are the hereditary changes which Kammerer 
established in Alytes obstetricans—the midwife toad. 
With them copulation normally takes place on dry land. The 
male extricates from the female the string of eggs, winds it round his 
hind legs and carries it about until the eggs are ready. Then, and not 
till then, he enters the water where the larvae escape. If, however, one 
keeps these toads in a high temperature (25-30 C.) they enter 
the water to cool themselves and abandon their normal way of 
manipulating their brood because the string of spawn swells in water 
and does not remain sufficiently sticky to allow the male to fasten 
it to his thighs. The animals become gradually accustomed to 
live in water, and continue to carry on the business of reproduction 
there, even when the temperature is normal. As soon as the new 
instinct has become sufficiently established with the parents they 
beget offspring, which at a normal temperature go of their own accord 
into water to deposit their eggs, and also produce eggs more numerous 
than, and somewhat different from, those of the normal toad. Further, 
the males of this succeeding generation develop thumbs and fore­ 
arms of a character which enables them to perform the difficult task 
of holding the females during copulation in the water. 
q 5 & 6 The likeness of offspring to their parents is extremely great and 
goes into many details; this we frequently overlook because a diver­ 
gence strikes us more than a similarity. A similarity becomes 
striking when it is a question of familiar peculiarities. These often 
relate to exterior unimportant peculiarities. Our collection contains

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