ARTIFICIAL PARTHENOGENESIS IN CUMINGIA 3 



them with ox-serum followed by hypertonic sea-water. No 

 cytological study of these eggs was made, and from the brief 

 notes the authors have published it is impossible to say whether 

 the results of this treatment correspond with those set forth in 

 the following pages. 



The technique of these experiments is simple. A small flask 

 of sea-water is suspended in a beaker of water and warmed over 

 a flame till the temperature of the water in the flask is sUgh-tly 

 above that to which one wishes to expose the eggs. The intro- 

 duction of a little cool sea-water with the eggs lowers the tem- 

 perature somewhat, and it is an easy matter to keep it constant 

 for an hour or more within the rather wide limits necessary for 

 these experiments. 



The temperatures to which the eggs were subjected varied 

 from 32°C. to 37°C., and the length of the exposures from 1^ 

 to 90 minutes. The treatment with hypertonic sea-water was 

 also varied, and the interval between the two treatments, as 

 well as the interval between the spawning of the eggs and the 

 beginning of the experiment. A detailed study of these varia- 

 tions is given in a later section and in the tables. 



Some eggs were fertiUzed, in order that a comparison might 

 be made between the normal and the parthenogenetic develop- 

 ment. In fertilizing eggs, care must be taken to avoid poly- 

 spermy by using a dilute sperm suspension. 



b. Microscopic methods. Material was taken from the ex- 

 perimental cultures at varying intervals, and preserved for cyto- 

 logical study, and corresponding series were made of the nor- 

 mally fertilized eggs. Almost all of this material was preserved 

 in Bouin's fluid. A few sets were fixed in Mme. Danchakoff's 

 modification of Zenker's fluid, in which 8-10 per cent formalin 

 is substituted for the glacial acetic acid. 



As the eggs are very small, they were stained in toto before 

 embedding. Conklin's picro-hematoxylin was found to be 

 most useful for this purpose. Some of the material was stained 

 with borax carmine, but this makes the sections opaque and 

 practically valueless unless they are bleached with chlorine gas. 



