Detenu/ ?iat/oii of Sex in Hydatina seuta 3 



II MATERIAL AND METHODS 



In the latter part of April, 1906, Hydatina senta was discovered 

 in great numbers in a small pool on the Palisades of New Jersey 

 near Grantwood. The pool was fed by a little stream or ditch 

 which carried away the drainage from several cottages. The 

 ditch was an extremely favorable place for the growth of Euglena 

 viridis which collected in large patches on the sides and bottom. 

 Immense numbers of Euglena floated down into the pool at the 

 end of the ditch and served as food for the rotifers which abounded 

 there in countless thousands. Sometimes as many as 150 to 250 

 individuals could be drawn up by a pipette in a few cc. of water. 



About May 15 the pool dried up completely. The ditch still 

 contained water but no rotifers were found in it after May 20. At 

 this time there were innumerable larvae of insects in the ditch and 

 perhaps they exterminated the rotifers by feeding upon them. 



In all experiments each individual female was isolated in a 

 square or round watch glass which contained about 5 cc. of water 

 and fed with Euglena, other protozoa and bacteria. 



In order to obtain the Euglena and other protozoa a culture of 

 horse manure and water (one to two ounces to a quart) was made, 

 inoculated with Euglena and allowed to stand for two to three 

 weeks at room temperature. At the end of this time the green 

 coating of algae, Euglena, etc., could be removed from the sides 

 of the glass jar and served as an excellent food for the rotifers. 



Great care was taken to keep these food cultures uncontami- 

 nated by rotifers. All watch glasses were placed in hot water 

 after each experiment in order to destroy all eggs which adhered 

 to the sides, thus preventing contamination of the following experi- 

 ments by eggs of the preceding ones. 



The experiments at temperature of 24° to 29° C. were con- 

 ducted in an incubator. Those at a temperature of 20° to 22° C. 

 were conducted on the laboratory tables at room temperature, 

 while those at a temperature of 14° to 15° C. were carried on in an 

 ice chest. 



These rotifers are exceedingly hardy and can be very easily kept 

 in the laboratory throughout the year. In May of 1906 a Euglena 

 culture was prepared in a glass jar containing 2000 cc. of water 



