OLFACTORY REACTIONS OF SPHEROIDES 365 
times bitten, received less attention and never was opened. When 
packets made of cotton cloth were substituted for those of cheese 
cloth, similar results were obtained; i.e., the one with meat was 
bitten open, the powerful jaws of Spheroides cutting through the 
cloth as if it had been tissue paper. From these tests it became 
evident that, in order to obtain any extended series of reactions 
to the packets, they must be constructed to withstand a severe 
biting as well as permit the escape of odorous material. This 
end was accomplished by covering with cheese cloth a pair of 
tea strainers made of tin and fine wire netting, one of which was 
filled with dogfish meat, and the other with cheese cloth. The 
fish were not adverse to biting such an object, which was at the 
same time flexible and impossible to tear apart, and, accordingly, 
they were used throughout the experiments to be described. 
With two packets reconstructed in this manner I again pro- 
ceeded to test the fish, about a dozen in number. For fifteen 
minutes after the packets were suspended in the aquarium, the 
puffers bit actively at both, but decidedly more at the one con- 
taining meat. At the end of that time, they were observed for 
one hour, and a record was kept of the number of times each 
packet was bitten, the relative positions of the two being changed 
every fifteen minutes. The packet containing meat received 
42 bites, the one with cheese cloth 4. These tests show con- 
clusively that the puffer is able to discover concealed food. 
That sight plays an important part in the search for edible 
substances is made clear from the fact that the packet of cheese 
cloth is occasionally seized by the hungry fish. Moreover, if a 
wad of filter paper attached to the end of a wire is drawn through 
the water, it is pursued and taken into the mouth as eagerly as 
if it were meat. But, whereas the meat is always swallowed, the 
filter paper, although often drawn into the mouth several times, 
is ultimately discarded. Similar reactions were observed by 
Parker (11) in the killifish. That sight will not explain their 
final discrimination between edible and inedible material is quite 
evident. 
I next planned a series of experiments to ascertain the part 
played by the olfactory apparatus in the reactions of the fish to 
