EARLY DEVELOPMENT IN THE FROG. 317 



2. Routine and Methods of Handling Eggs. Clasping frogs 

 (Rana pipiens] were obtained from a local dealer and placed in 

 a large cement aquarium arranged to simulate natural conditions 

 as nearly as possible. The temperature of the water was kept 

 between 5 and 9 C. There was no difficulty in obtaining all 

 the eggs that could be used ; and with a little patience they could 

 be had as soon after deposition as desired. As many as five 

 females have been seen spawning at one time. Shortly after 

 deposition each egg mass was given a number, the jelly cut into 

 bits containing ten to twenty eggs each, and then placed in a 

 gallon jar of the cold aquarium water. About an hour before 

 being introduced into experimental conditions the jar of eggs was 

 removed to the laboratory to warm slowly up to the room 

 temperature (17 i C.). 



For the modification of development the following chemicals 

 were used: potassium cyanide, formaldehyde, potassium per- 

 manganate, mercuric chloride, magnesium chloride, lithium 

 chloride, hydrochloric acid, sodium hydrate, and ethyl alcohol. 

 The method of handling the eggs varied somewhat with the 

 chemical used. Eggs treated with KNC, CH 2 O, HC1, NaOH 

 and C 2 H 5 OH, were placed in liter Erlenmeyer flasks filled almost 

 full and stoppered. For the other chemicals, glass finger bowls 

 of 3OO-C.C. capacity, one- and two-liter candy jars were used and 

 covered with glass plates to prevent evaporation. 



In a given experimental series similar glassware was used, 

 each vessel containing approximately the same number of eggs 

 from the same female. In every case one vessel of the series 

 was used as a control and was treated in the same way as regards 

 stoppering, changing of fluids, etc. Eggs from the same females 

 developing in liter Erlenmeyer flasks filled nearly full and stop- 

 pered, and in the same volume of water in open dishes did not 

 differ in rate or manner of development up to some time after 

 hatching, provided the water was changed once in twenty-four 

 hours and when there were not more than 100 c.c. of egg mass 

 in the stoppered flask. Especial care was taken to use no more 

 than 15 to 20 c.c. of egg mass in stoppered vessels, and to change 

 solutions in all experiments daily. 



As will be noted later, the frog egg undergoes a tremendous 



