ENTOMOSTRACA AND PHYLLOPODA. 259 



the heat of early summer or late spring. Dr. Packard, 

 describing a visit to a pond where these creatures had 

 been found on May 2d, but from which they had all 

 disappeared by May 13th, says, " It seems from this 

 quite evident that the animal probably dies off at the 

 approach of warm weather, and does not reappear until 

 after cool weather sets in late in the autumn, being rep- 

 resented in the summer by the eggs alone; and thus 

 the appearance and disappearance of this Phyllopod is 

 apparently determined mainly by the temperature." 



A vessel full of water in which Branchipus is floating 

 on its back is a strangely beautiful and interesting sight. 

 The pale reddish or flesh-colored bodies rising and fall- 

 ing in long curves, with their numerous broad feet 

 waving together rhythmically, make a living picture 

 long to be pleasantly remembered. 



Those readers who desire to pursue the subject, es- 

 pecially in respect to the anatomy and development of 

 these crustaceans, are referred to Mr. C. L. Herrick's 

 " Crustacea of Minnesota," published in the twelfth an- 

 nual report of the State Geologist, and to Prof. A. S. 

 Packard's " Monograph of the Phyllopod Crustacea of 

 North America," issued in the twelfth annual report 

 of the United States Geological and Geographical Sur- 

 vey of the Territories, Dr. F. V. Hayden in charge. 

 12* 



