stand, or by the time which ehipses during their transportation 

 to the laboratory, and we cannot at present attach very great 

 importance to the results which have hitherto been ol)tained. 



AVe expect soon to l)e able to extract gases from w'ater by 

 nu'aus of an air pump and then we shall be in a position to ol)- 

 tain results wdiicli Avill not be influenced by the conditions men- 

 tioned above, and, provided we shall be able to have collections 

 carefully made at Havana, the work can very easily be con- 

 tinued and completed here at the University. 



Since early in the summer of 1897 we have made regular 

 determinations of dissolved oxygen and of carbon dioxide in 

 •samples taken from the Illinois Eiver and from Thompson 

 and Quiver lakes, but the earlier results are less reliable than 

 those obtained during the last six months, and these later results 

 are themselves not sufficiently reliable to be made at present 

 the basis of any general conclusions. 



Yours very respectfully, 



^KTHUR W. Palmer, 



Professor of CJicinhtrij. 



REPORT OF THE ENTOINIOLOGICAL ASSISTANT. 



I'tt tlic ])ircctor of tlw LaJiovoforii. 



Sir: During the season of lrt97 I was in the field, prima- 

 rily for entomological observation and collection, from June 

 !29 to August 13, giving attention particularly to the gathering 

 of information and material for use in completing our work on 

 O(]on<it(t and Molhisca. In 1898 two visits to the field were 

 made for work on Odoiuita, Kplicmer'ida, and Molhtscn ; a week 

 in spring, from April 19 to 2"), and two weeks in midsummer, 

 from June 21 to July 7. 



The accumulations of material and notes were already 

 sufficiently large for group studies at the beginning of the two- 

 year period covered by this report. Every opportunity has 

 been taken to make desirable additions to them, and they now 

 stand as a superl) basis for the study of any group of aquatic 

 forms. The material is all arranged by orders, and consists of 

 about 4, '250 vials and bottles of specimens. 



There are now in various stages of preparation four papers, 



