36 
IOWA ACADEMY OF SCIENCES. 
caves has rendered both brilliant colors and large eyes useless, 
and thus both have been rigidly suppressed. 
The presence of phosphorescence in so many animals which 
are supposed to be sightless, e. g., pennatulids, gorgonians and 
hy droids, is hard to explain.* Indeed, it is not properly 
within the scope of this paper to explain it. A suggestion 
occurs to me, however, that may be worth noting. These 
animals feed, for the most part, on minute Crustacea and on 
protozoa. Most Crustacea, and more particularly their embryos, 
have functional eyes. May they not be attracted by light, as is 
the case with shallow- water forms? The protozoa are gener- 
ally without distinct organs of vision, but many of them are, 
nevertheless, apparently attracted by light. If this is true, 
we have a reason for phosphorescence among the fixed coelen- 
terates. It attracts the prey. This, to my mind, is more 
plausible than the theory that it is a protective contrivance. 
We may thus imagine the bottom of the sea to be for the 
most part dark, but with limited areas where are congregated 
phosphorescent animals that give forth sufficient illumination 
to render striking colors, particularly red, yellow and green, 
distinctly visible, enabling them to play the same role that 
they do in shallow water, and bringing them within the prov- 
ince of the same laws. 
NOTES ON THE HEMIPTERA OF NORTHWESTERN 
IOWA. 
BY HERBERT OSBORN. 
Prom the difference in geological and floral conditions of 
the northwestern part of the state, we might naturally expect 
a somewhat interesting insect fauna. Occasional specimens of 
species, rare or unknown in the central part of the state, have 
come to hand and, especially in Hemiptera, have served to 
strengthen a desire to investigate more thoroughly the fauna 
in this order. Many of these additions have been due to the 
* Verrill thinks that phosphorescence in these cases is of value in warning- away 
enemies from the nettling- cells. I have been unable to find nematocysts among the 
gorgonidae and have never seen them mentioned as found among pennatulids. They 
are seldom of large size among the hydroids. 
