ALBERT C. JENSEN. 



from the lake before nauplii appeared there, and precautions 

 taken to eliminate all eggs. Undeveloped females were placed 

 in this water, where they developed normally and deposited eggs 

 similar in appearance to fertilized ones. These eggs produced 

 males and females, which developed normally and as far as could 

 be observed could not be distinguished from those coming from 

 fertilized eggs. A large proportion of the hatch was females. 

 Both methods are evidently used during the summer months. 



According to my records all of the brine shrimps die during 

 the winter months, probably due to the lowered temperature. 

 These observations do not harmonize with those of Talmage, 

 who says: "I have taken them in the midst of winter, when the 

 temperature of the water was far below the freezing point." 



Statements made by Gilbert that the ancestors of Artemia 

 may have lived in the fresh water of the basin, led to an experi- 

 ment to determine the effect of different concentrations of salt 

 water upon this animal. By using distilled water and the 

 process of evaporation, solutions were prepared having a specific 

 gravity as follows: 



On March 28 eggs were put into the above solutions. March 

 30, 44 hours later, nauplii had emerged and were swimming 

 about in solutions I, 2 and 3 and in 4 they were emerging from 

 the eggs. In the latter I observed the ocellus, also one or two 

 pairs of appendages that were moving as if trying to free the 

 body from the shell. By April 10 nauplii were emerging in 

 solution 5 and not until April 13 did the eggs in solution 6 begin 

 to hatch. By this date nauplii were also emerging from eggs in 

 the lake. On May 5 a few nauplii appeared in solution 7, but in 

 solutions 8 and 9 no nauplii had emerged. To test if the eggs 

 in these last two solutions were fertile, a few were put into a 

 less dense solution where they hatched readily. In solution I 



1 The specific gravities herein given are the uncorrected hydrometer readings. 



