564 Wisconsin Academy of Sciences, Arts, and Letters. 
by an expansion of the cloaca. The foot glands are very long, 
slender, and slightly club-shaped. 
The retrocerebral sac is extremely long, clear, and vacuolate; 
the subcerebral glands are less than half the length and usually 
include aggregations of baeteroids, rendering them partly opaque. 
The very large eye-spot is at the posterior end of the small, sac¬ 
cate ganglion. 
Total length 750-1000/*,; toes 50-60/*,; trophi 90-100/*. 
Notommata copeus is common in weedy ponds everywhere. In 
certain places it is found inhabiting a jelly-case, secreted by the 
integument; occasionally a blue-green alga is attached to the in¬ 
tegument and grows through the jelly-case. This species is usually 
regarded as being strictly a plant-feeder; this may be a matter 
of necessity rather than choice. Some time ago some material 
was forwarded by Dr. Whitney from Lincoln, Nebraska, consist¬ 
ing mainly of colonies of the free-swimming Lacinularia ismai- 
loviensis (Poggenpol), but containing also some individuals of 
Notommata copeus. These were feeding vigorously on detached 
individuals from the Lacinularia colonies, to which they held so 
tenaciously that the captor could be transferred to a slide without 
letting go its hold on the captive. It was then discovered that 
the unci are, contrary to the general impression, very mobile and 
capable of being opened out sufficiently to make them parallel 
with each other, and also that they are very effective in capturing 
and tearing the prey. 
The specific name copeus has been used in preference to cen¬ 
trum, partly because it appeared to receive general acceptance 
after Gosse’s names labiatus and ehrenbergii had been discarded, 
and also because it was originally attached to the more correct 
description. Ehrenberg’s citation in Infusionsthierchen under N. 
centrura of Abh. Akad. Wiss. 1832; 438 is incorrect; both centrum 
and copeus were published simultaneously and for the first time 
in the Abhandlungen for 1833 (published in 1834). Centrum 
has page priority, but copeus has a better description; as is well 
known, Ehrenberg described the animal with retracted auricles 
as N. centrura and with extended auricles as N . copeus. The 
recommendations of the International Code of Zoological Nomen¬ 
clature is that, “all other things being equal, page precedence 
should obtain”, but “show preference to the best described, best 
