MONSTROSITIES 291 



embryos from half an egg 5 ; that Mr. Edward B. Wilson of Columbia 

 College, New York, ' has produced out of one egg of Amphioxus, 

 twins of half the normal size, and by varying the experiments, 

 a sort of Siamese twins from one egg were produced.' 1 



A number of other experiments on ova are mentioned by Mr. 

 Thomson, and the conclusions he has come to from this review are 

 that: 



(1) There is a great deal of life -in an egg; three-quarters, a 

 half, or a quarter of an egg will, under favourable conditions, form 

 a complete larva. 



(2) There is no little plasticity in the germ ; the segmentation 

 may be profoundly altered, the shape of the young embryo may be 

 greatly changed, and a new type of larva may be produced, yet the 

 inherited characteristics are strong, for the experiments show a 

 marked tendency in the germ to reach a normal result by an 

 abnormal path. 2 



With regard to the non-inheritance of acquired characters, he 

 says : ' How many ova are there which float in the sea, and in other 

 media ; these are now, as similar ova have been in the past, 

 exposed to the influences of very complex physical and chemical 

 conditions. That their living stuff may be greatly affected the 

 results of experimental embryology show. It is likely that the 

 same is true in Nature's great laboratory, and the results, being 

 germinal, may be transmissible. We need not be in haste to 

 exclude the direct influence of the environment from among the 

 primary factors of evolution.' 



1 If all this can be established, it may go a long way towards demonstrating that our 

 two halves were originally a fusion of two embryos with suppression of a right and left 

 half of each. 



2 Perhaps the embryo may be likened to a crystal ; you may break a crystal in pieces, 

 and each piece, under proper conditions of food and stimulus; will grow again into a 

 crystal like its parent. 



