436 
in which the forms are named. Limnodrilus is eaten voraciously by the 
Amblystoma larvee and by Diemyctylus. Dieinyctylus has been observed a 
few times to take Simocephalus. 
The insects that accidentally fall into the pond are captured by the 
Gyrinidse and Hygrotrechus. 
The Corethra larvee feed on ostraccda and possibly cther forms in this 
pond. Miall (°95, page 115) says, “Corethra larvee feed upon small aquatic 
animals such as Ephemera-larvie, Daphnia, or Cypris.” The Hydrophylidee 
feed on the decaying organic matter. The Dytiscide have not been observed 
feeding in this pond, although they are known to be Garniverous, Kellogg 
(04, p. 258). The lervee of the Anura of this pond are rather omniverous. 
They eat filamentous alge, desmids, diatoms, protozoa, ostracoda and de- 
caying organic material. There seems to be very little if any discrimina- 
tion in the selection of food. Not all of the material eaten contributes to 
the nutrition of these larve. The rate of digestion in cold blooded verte- 
brates has been shown by Riddle (09) to vary directly with temperature. 
However, at ordinary temperatures many organisms pass through their 
alimentary tracts unchanged. In the faeces of iarvie placed in tap water, 
Ocdogonium, Closterium and Doccidimm are common. From the alimentary 
tracts of larvee kept for 5 days in water, which had been previously boiled, 
have been taken Huglena, Phacus, Spirogyra, Oedogonium, Closterium, 
Doccidium. The filamentous algzee and Closterium were in part disinte- 
grated. The Huglene were very active. In another series that was kept 
10 days, Ostracoda (Candona?) were found alive in the large intestine of 
six specimens. These facts indicate that the nutrition is derived from 
dead organic matter (filamentous alge and Closterium) and that the in- 
clusion of other, living organisms is accidental. 
In connection with food relations may be mentioned the mechanical 
comminution of plant debris. When plants die in the pond, they stand fot 
a time, then fall on the surface of the water where they float for a while 
and then sink. During this period they are being softened by the processes 
of decay. Their comminiution is due to the action of the Ostracoda, es- 
pecially Cypridopsis and the aquatic beetles belonging to the families Hy- 
drophylidze avd Dytiscidze. The specific gravity of the former is slightly 
greater than water and that of the latter slightly less. A piece of floating 
plant stem is covered with Ostracoda. A bit of the stem is often torn off 
by one of these ostracods. The ostracod remains attached to it until if 
