44 THE UNIVERSITY SCIENCE BULLETIN. 
appended no bibliography and gave no hint of an acquaintance 
with the significant results of the recent European workers. 
His classification of respiratory types, however, is fairly stated 
if his interpretation of function be ignored. 
I. Dorsal reservoir: Corixide, Belostomatide and Naucoride. 
II. Abdominal channel: Notonectide. 
III. Tube type: Nepide. 
The Corixide make contact with the air by the thorax, while 
the Naucoride and Belostomatidz connect with the tip of the 
abdomen, as do the Notonectide and Nepidz. The last named 
family have prolongations of the eighth abdominal segment, 
which afford a connection between the air and the spirac- 
ular openings, enabling these insects to remain at some dis- 
tance below the surface. 
In matters of meeting the problem of air supply the Co- 
rixide, though less profoundly modified as to structure than 
the Nepids, are nevertheless the most independent in their be- 
havior of all the water bugs. The problem of aquatic respira- 
tion then is a complex one, and involves further study. 
There is yet another phase of hydrobiology that should be 
mentioned in connection with this chapter. It is the mastery 
of the physical properties of the water relating to the surface 
film. Brocher has given us a splendid paper on the funda- 
mentals of this question, to which the reader is referred. He 
shows the clever devices that enable insects to walk upon the 
water, to rise out of the water, to break the surface film from 
below in making contact with a vital supply of free air, as well 
as to enter the water from above. 
It is interesting to watch a Notonectid just alighted upon the 
water maneuver to submerge. Encased in nonwettable ma- 
terial, the body is buoyed up, and to submerge, the tip of the 
hind limb, which is wettable and attracts the surface film, is 
dipped into the water before the head and the film drawn thus 
over the back, covering the bug and placing him below. In 
the light of Brocher’s work, there are many interesting experi- 
ments that suggest themselves concerning the manner in which 
the water bugs have met and solved the problems of their 
elected environment. 
