RESULTS OF CONSANGXnNITY 119 



which are thus, all of them, his sisters, daughters, or aunts ; 

 and yet the race shows no signs of degeneracy. And in the self- 

 fertilisation which occurs among various species of crustaceans, 

 etc., already mentioned — self-fertiUsation often obligatory in the 

 interest of the preservation of the species — ^it does not appear 

 that any sort of degeneracy has been noticed in the species which 

 are adapted to this method of reproduction. 



To sum up, we may say that consanguinity is not in itself a 

 necessary cause of biological degeneracy. Where an unfavour- 

 able variation, through some cause or other, already exists, con- 

 sanguinity tends to favour its dissemination and increase, and 

 in so far consangidnity is a frequent cause of degeneracy ; but 

 where no morbid variation already exists, and in the case of old 

 and well-adapted species, consanguinity may be practised with- 

 out any disadvantageous results. Indeed, as consanguinity 

 accumulates homogeneous ids in the germ-plasm, families which 

 are thoroughly healthy in all their members may practise con- 

 sanguinity with advantage, as every fresh intermarriage will 

 result in an accumulation of favourable determinant complexes — 

 i.e., of healthy elements. 



