Natural Selection of Species. Ill 



istic of the breed will depend on whether the habit be continued or the 

 new anatomical condition be useful and used by the offspring. A con- 

 tinuance of the conditions through succeeding generations are necessary 

 to fix any new characteristic. It is constantly remarked by naturalists 

 that the latest modifications of type in any race are more liable to varia- 

 tion than the older ones. In the human race the latest anatomical 

 modifications are to be found in the relative lengths of the legs and 

 arms, formation and amplitude of their muscles and particularly in the 

 organs of speech and the development of the cerebral hemispheres. So 

 I think we will find more cases of congenital reversion or arrest, as well 

 as more cases of superior development to relate to these parts than to 

 the parts which we possess more in common with the lower animals. 

 Many cases of idiocy and imbecility are on record, which have resulted 

 from the transmission of temporary cerebral debility on the part of par- 

 ents. One case is cited of an idiot born to parents who were both 

 drunk when he was begotten, but who were ordinarily intelligent when 

 sober. Another case is given of an imbecile born so in consequence of 

 a strong mental disturbance of the mother from seeing an idiot during 

 the period of gestation. ' 'A medical practitioner of Douglas in the Isle 

 of Man, mentions the following case : A man's first child was of sound 

 mind ; afterwards he had a fall from his horse by which his head was 

 much injured. His next two children proved to be both idiots. After 

 this he was trepanned and had other children and they turned out to be 

 of sound mind. "* It is often observed that children born to foreign 

 parents of the working classes after their immigration to this country 

 are brighter and more intelligent than the children of the same parents 

 born before they left Europe. 



Childhood is said to be the impressible age. Lessons learned and 

 habits formed in childhood are more fixed than those of later date. But 

 the embryonic or prenatal state is far more plastic than childhood, and 

 it is while in this state that all the essential parental characteristics are 

 impressed upon it, whether such characteristics be permanent or only 

 temporary to the parents. The plasticity of the embryonic stage is es- 

 pecially observable in fish culture, the natural conditions not being pre- 

 cisely imitated in artificial hatching. The number of malformations 

 among the embryo of the artificially hatched salmon, trout, whitefish, 

 &c. , is sometimes so great as to make serious inroads on the profits of 

 the business. A very common monstrosity consists in having two heads, 

 another of having a double backbone and spinal cord. In some cases 

 the sense organs or the locomotive organs are defective, in others there 

 is an anomalous development of the intestinal system. Such malforma- 

 tions are common among carp and still more so among gold fish ; and 

 1 Combs' Constitution of Man, 160. 



