MIMICRY. 



179 



fore be aided by a pre-existing tendency, and we must 

 hence regard it as hereditary." 



Haeckel Hkewise propounds a law of individual 

 adaptation, which expresses the fact that, notwithstand- 

 ing the closest kinship, individuals diverge in many ways. 

 The cause of this difference, chiefly conspicuous in the 

 individuals of the same litter or brood, is, so far as it 

 is not due to adaptation, inherent in the germs, and is 

 transferred to them by fluctuations and differentiations 

 in the conditions of nutrition in the parems, mostly be-, 

 yond our ken. Other phenomena of indirect adapta- 

 tion are exhibited in the occurrence of malformations, 

 of which the causes must be looked for only in dis- 

 turbances of nutrition in the parental organisms by 

 which the progenitors themselves were not percepti- 

 bly affected. Here also belong the cases, in which 

 influences which have affected one sex only are mani- 

 fested exclusively in posterity in the same sex. As 

 may be seen, these processes, of which the initia- 

 tion is entirely withdrawn from observation, are 

 closely connected with the most obscure province of 

 heredity. 



An extremely interesting and important form of 

 adaptation is the so-called mimicry, or protection by 

 means of colouring and form. The first discoveries 

 on this subject were made by Bates, the well-known 

 " Naturalist on the Amazon ; " the greater part were 

 subsequently added by Wallace. In South America, 

 the family of butterflies named Hehconida is extraor- 

 dinarily extensive; they are remarkable for their 

 elongated wings, body, and antennas, and for the beauty 

 of their colours. It might be imagined they were ex- 



