372 ANIMAL BIOLOGY 



have been performed, many of which have been inter- 

 preted in different ways, and there is still a difference of 

 opinion on the question among students of heredity. 



Most of the change that has been produced in domestic 

 plants and animals has been effected, not by the trans- 

 mission of characters acquired by the parents, but by 

 means of the preservation of variations which originated 

 in the germ cells. The appearance of six-toed cats, Ancon 

 sheep, albinos and runnerless strawberries is due to some 

 change in the germ plasm, and there is no doubt that such 

 variations of germinal origin tend strongly to be trans- 

 mitted. The selection of germinal variations might in 

 time effect very great changes, and it is held by many 

 biologists that the whole process of evolution has been 

 brought about by this method. 



It was formerly a widespread belief that various peculi- 

 arities can be impressed upon unborn children by the ex- 

 periences of the mother during pregnancy. Sometimes 

 children are born with a mark or blemish of some sort 

 which is often attributed to a fright, desire or other strong 

 feeling on the part of the mother. There are skin markings 

 called naevi due to an enlargement of the cutaneous 

 capillaries that sometimes have a certain resemblance, 

 more often fancied than real, to strawberries, black- 

 berries, liver or some other object for which the expectant 

 mother may have had a strong craving. When a child 

 is born having any sort of blemish the history of the 

 mother is inquired into to discover some experiences 

 which might account for it, and out of the numerous 

 experiences that have occurred something is frequently 

 found that satisfies the enquirer. Stories like the follow- 

 ing are typical : Mrs. A. on putting her hand into a flour 

 bin was frightened by a mouse which ran upon her arm. 

 Her child born some weeks afterward had a reddish patch 



