Chap. XXII. CAUSES OF VARIABILITY. 257 



reproduction would likewise affect their product,— that is, the 

 offspring thus generated. 



The period of life at which the causes that induce variability act, 

 is likewise an obscure subject, which has been discussed by various 

 authors. 49 In some of the cases, to be given in the following chapter, 

 of modifications from the direct action of changed conditions, which 

 are inherited, there can be no doubt that the causes have acted on 

 the mature or nearly mature animal. On the other hand, monstrosi- 

 ties, which cannot be distinctly separated from lesser variations, are 

 often caused by the embryo being injured whilst in the mother's 

 womb or in the egg. Thus I. Geoffroy Saint-Hilaire 50 asserts that 

 poor women who work hard during their pregnancy, and the mothers 

 of illegitimate children troubled in their minds and forced to conceal 

 their state, are far more liable to give birth to monsters than women 

 in easy circumstances. The eggs of the fowl when placed upright 

 or otherwise treated unnaturally frequently produce monstrous 

 chickens. It would, however, appear that complex monstrosities 

 are induced more frequently during a rather late than during a very 

 early period of embryonic life ; but this may partly result from some 

 one part, which has been injured during an early period, affecting 

 by its abnormal growth other parts subsequently developed; and 

 this would be less likely to occur with parts injured at a later period. 51 

 When any part or organ becomes monstrous through abortion, a 

 rudiment is generally left, and this likewise indicates that its 

 development had already commenced. 



Insects sometimes have their antennae or legs in a monstrous 

 condition, the larvae of which do not possess either antennae or legs ; 

 and in these cases, as Quatrefages 52 believes, we are enabled to see 

 the precise period at which the normal progress of development 

 was troubled. But the nature of the food given to a caterpillar 

 sometimes affects the colours of the moth, without the caterpillar 

 itself being affected ; therefore it seems possible that other characters 

 in the mature insect might be indirectly modified through the larvae. 

 There is no reason to suppose that organs which have been rendered 

 monstrous have always been acted on during their development ; the 

 cause may have acted on the organisation at a much earlier stage. 

 It is even probable that either the male or female sexual elements, 

 or both, before their union, may be affected in such a manner as to 

 lead to modifications in organs developed at a late period of life ; in 

 nearly the same manner as a child may inherit from his father a 

 disease which does not appear until old age. 



49 Di. P Lucas has given a history several memoirs by M. Dareste here- 

 of opinion on this subject : ' Hered. after referred to are of special 

 Nat..' 1847, torn. i. p 175. value on this whole subject. 



30 ' Hist, des Anomalies,' torn. iii. 5a See his interesting work, ' Meta- 



p. 499. morphoses de 1'Homme,' &c, 18G2, p. 



« Ibid., torn. iii. pp. 392, 50£ The 129. 



