Vol. XXII. March, 1912. No. 



BIOLOGICAL BULLETIN 



"STRAINS" IN IIVDATINA SENTA 



D. U. WHITNEY. 



In .i lormer paper results of experiments upon t\\<> \ 

 the roiiier Hydatina scuta were given in regard t<> tin- production 

 ot OIK- hundred generations of females without the appearance 

 ..I males in either race. These experiments have In en extended 

 further fur al>uiit seventeen months and as they are <-onrlnde.! 

 it seems desirable to record the results obtained partly a< a 

 iilii niation of the earlier conclusions and partly because they 

 turni \ idence which shows that there exists diffrreiit races '>r 

 strain- < >r lines within this particular species of Hydatina scntn. 



In the furmer paper it was shown how readily male --prodiu -inu 

 females could be produced in newly made dilute unconkrd 

 hoi -e manure cultures and also how readily the male-pro- 

 ducing lemales could be repressed in newly made concentrated 



ked hoi-e manure cultures. 



In the piv-eiit paper the parallel history of three r, ( ces of 

 rutiler- .1, H, and C is given. Races B and C are the same 

 races ii|iun \\hich the former conclusions were based while i 

 .1 i- .in additional one. Races A and B are si-ter rate-, both 

 ha\ in- tle\ eloped from one fertilized egg while race ( ' is unrelated 

 to races .1 and B except in as far as all three races came from 

 the s.inie general culture of rotifers which was originally collected 

 at ( irantuood. New Jersey, in 1906. 



Race- .1 and B were always conducted in a parallel -, ries but 

 race < ' \\as not put into the parallel series until it \va- in the 301 h 



Deration. During this early period of the three race- before 

 they \\erc all put into the parallel series the food \\a- from mis- 

 cellaneous protozoa cultures of various ages made in dilute un- 

 cooked hor-e manure media. The summary ..f the early history 



205 



