EVIDENCES OF EVOLUTION 61 



in 1871 the waters of the upper part swept 

 over the dam and reduced the salinity in 

 the lower part. Thereafter great numbers of 

 a tiny brine-shrimp, Artemia salina, were 

 observed in the lower part, having been 

 presumably washed in. After a time the dam 

 was repaired, the water gradually regained 

 its great salinity, and the brine-shrimps in 

 the course of their rapid generations lost the 

 well-developed caudal fins characteristic of 

 Artemia salina and became like another 

 form without caudal fins, Artemia mil- 

 hausenii. Passing from observation to ex- 

 periment, Schmankewitsch found that grad- 

 ual concentration of the water led to the 

 replacement of typical forms of Artemia 

 salina by forms like Artemia milhausenii, 

 and he also showed that if the forms without 

 caudal fins were kept in brine which was 

 gradually diluted, a pair of conical promi- 

 nences, each with a bristle, appeared after 

 some weeks at the end of the tail. Schman- 

 kewitsch did not regard the change he 

 observed as a transformation of one species 

 into another, and it seems fairly clear that 

 there is no species Artemia milhausenii. 

 What he did show was that alterations in the 

 salinity of the water are, in the course of 

 generations, followed by slight changes in the 

 form of the tail. Bateson and others have 



