CONTROL OF SEX BY FOOD IN ROTIFERS 273 



Diaschiza sterea 



In March of 1915 four fertilized eggs of Diaschiza sterea were 

 isolated from a battery jar containing miscellaneous varieties 

 of animals growing in a stable tea (horse manure) solution. 

 This jar was made in September of 1914 and had been left stand- 

 ing since that time without a renewal of stable tea. These fer- 

 tilized eggs were put into fresh tap water for a few hours and 

 then later a little stable tea was added to the water. Within 

 a short time the eggs hatched and produced females. These 

 females were fed upon the colorless flagellate, Polytoma, and 

 reproducing readily produced a culture of many females but 

 no males. 



The Polytoma was reared in a solution of stable tea as follows : 

 800 grams of fresh horse manure mixed with 1200 cc. of tap 

 water, was cooked in an autoclave at 15 lbs. steam pressure for 

 one hour and then 1000 cc. of the liquid was pressed out of the 

 cooked manure. This solution, hereafter called stable tea, 

 was used as a stock supply. One part of this stable tea and 

 three parts of sterilized water were mixed and inoculated with 

 Polytoma. Every day one-half of this culture was poured off 

 and replaced by a fresh solution of one part stable tea to three 

 parts water. In this manner a vigorous growing pure culture 

 of Polytoma was daily maintained. 



The Diaschiza sterea is a small rotifer, no larger than a small 

 paramoecium, and on account of their small size it was found 

 impossible to make individual pedigreed cultures of them. 

 Consequently all the experiments were made in mass cultures 

 either in small watch crystals or in depression slides. In a 

 weak solution of the Polytoma culture (1:2) the female rotifers 

 grew very readily but produced entirely female offspring. How- 

 ever, when these females were transferred to a weak bouillon 

 solution (2 cc. or 5 cc. of the stock bouillon solution to 148 cc. 

 sterilized water) to which pure pultures of Chlorogonium^ had 

 been added males appeared within a few days varying in pro- 



^This green flagellate formally has been known as Chlorogonium euchlorum 

 but recently Wille has reclassified it as Chlamydomonas euchlorum. Engler 

 u. Prantl, Pflanzenfam. Nachtrage I Teil, 2d Abt., 1911, p. 18. 



