The Making of Species 



normal colouring. Schmankewitsch made the 

 discovery that, in the case of the crustacean 

 Artemia, he could produce either of two species 

 according to the amount of salt in the water in 

 which these creatures were placed. He declared 

 that the anatomical differences between the 

 species Artemia salina and Artemia milhausenii 

 depended solely on the percentage of the salt in 

 the surrounding water. He further stated that 

 by adding still more salt he could change the 

 Artemia into a new genus Branchipus. More 

 recent observers have cast doubt upon these 

 results of Schmankewitsch. They, however, 

 admit that the degree of salinity of the water has 

 some effect on the form of the Artemia, although 

 they suggest that factors other than concentration 

 affect the result. In any case, it is now well- 

 known that changes in the environment effect 

 changes in the colouring of many Crustacea. 

 Pictet has shown that the alternating wet and 

 dry seasons in some tropical countries are the 

 cause of, or stimulus that induces, seasonal 

 dimorphism in some butterflies. He was able to 

 effect changes in the colouring of certain species 

 by means of humidity. 



The most important cases, from our point of 

 view, are those in which the application of 

 heat or cold to a pupa has affected the colour, 

 shape, etc., of the emerging butterfly. Here we 

 have but one factor, that of temperature. All 



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