THE TRANSFORMATION OF BRACHIONUS PALA INTO 

 BRACHIONUS AMPHICEROS BY SODIUM 



SILICATE. 



DAVID D. WHITNEY. 



In certain species of rotifers there is considerable variation in 

 the shape and form of the body of the female during the year. 

 Powers has shown that in one species of Asplanchna there are 

 three distinct phases through which a race may pass during one 

 season. The females in each phase differing from those in either 

 of the other two phases in both size and general form of the body. 

 He and Mitchell also have shown that in this particular species 

 these changes are somewhat corellated with the sexual stage of 

 the females which is produced by changes in food. Sachse 

 studied the variability of form in several other species and found 

 that the greatest variability occurred at the periods of abundant 

 food but he did not find that this variability was in any way 

 correlated with the sexual stage. Lauterborn made observations 

 upon Anuraea cochlearis and concluded that the variations of 

 form were due to changes in temperature. Wesenberg-Lund 

 made observations upon Asplanchna priodonta and concluded 

 that the variations were due to differences in density of the 

 water which varied according to the temperature. 



Recently H. K. Harring, custodian of the Rotatoria in the 

 United States National Museum, pointed out to me that Branchi- 

 onus amphiceros was a variation of Branchionus pala and that 

 it probably could be artificially produced from Branchionus pala 

 at any time by changes in diets. Knowing, however, only one 

 diet on which this species would thrive readily in the laboratory 

 it was impossible to test this suggestion. 



In considering the problem the self-evident fact was recalled 

 that the young stages of all living organisms must be supplied 

 with suitable materials out of which to build the various tissues 

 of their bodies. If an animal has a lime or a siliceous skeleton 

 it must be supplied with calcium or siliceous salts with which to 



