238 STUDIES IN GENERAL PHYSIOLOGY 



tion of the water slowly rose to 25 Beaum6, after which the salt 

 again began to be precipitated. 1 



In the course of this time progressive changes occurred in 

 Artemia salina, so that the Arteinia present in the year 1874 

 had the characteristics of the species A. mtilhausenii. These 

 changes in detail are the following: (1) The adult animals 

 of A. mtilhausenii are not so large as the adult animals of 

 A. salina. (2) Artemia salina has caudal bristles and caudal 

 appendages, which are lacking in Artemia mtilhausenii ; as 

 the concentration of the salt water increased, the caudal 

 bristles became progressively smaller. (3) The surface of 

 the gills is longer and narrower in Artemia salina than in 

 Artemia mtilhausenii. Ludwig (in Leunis's Synopsis) gives 

 only the first two points. According to this author, the 

 length of A. mtilhausenii is 6-8 mm. ; that of Artemia salina, 

 8-10 mm. Schmankewitsch was able to convert A. salina 

 into A. mtilhausenii by increasing the amount of salt in the 

 aquarium. 



2. By growing Artemia in salt water that was gradually 

 diluted, Schmankewitsch obtained a variety having the 

 characteristics of the genus Branchipus Schaeff. The differ- 

 ences are very slight. Artemia has eight, Branchipus nine, 

 footless terminal segments ; and, what is of importance to us, 

 Branchipus ferox attains a greater length, the less concen- 

 trated the salt water in which it lives. 



3. If we do not allow ourselves to be influenced by the 

 nomenclature of the systematist, the experiments and obser- 

 vations of Schmankewitsch show that the effect of the con- 

 centration of the salt shows itself most distinctly in the 

 longitudinal growth of the entire animal and of some of its 

 organs; and this always in such a way that with an increase 

 in the concentration of the solution the longitudinal growth 



1 Beaume's hydrometer is graduated, according to Wttllner, so that the point to 

 which it sinks in water is marked 0; that to which it sinks in a solution of fifteen 

 parts of sodium chloride and 85 parts of water, 15. Water of 8 Beaum6 therefore 

 contains about 9 per cent, salt ; that of 25" Beaume, about 23 per cent. 



