jy3 HOLMES [VOL. II. 



of chemoreception. In Carcinus the removal of the first 

 antennae as far as the first basal segment is followed by a 

 marked diminution of the power of reaction to chemical sub- 

 stances in the water. A Carcinus when the eyes are black- 

 ened over will find pieces of food when placed at some distance, 

 by the sense of smell. When the first antennae are removed 

 at the first basal segment, Bethe found that food maybe placed 

 as near as 10 cm. to the animal without calling forth any 

 efforts to obtain it. When the food is brought close to the 

 mouth or close behind the animal without contact with the body, 

 it is seized and eaten. The first antennae, therefore, while 

 they may be the main, are not the sole source of the reception 

 of olfactory stimuli. 



My own observations on Amphithoe led me, before becoming 

 acquainted with Bethe's results, to infer a double seat of the 

 sense of smell. In Amphithoe, as in Carcinus, the first anten- 

 nae seem to be the most important olfactory organs. While 

 the animal is at rest in its nest the antennules are kept swaying 

 to and fro in different directions, as if they were being employed 

 to explore the surroundings. If a small bit of flesh is held on 

 a needle or in a fine pair of pinchers and carefully brought 

 near the animal, the antennae check their random movements 

 and make one or more strokes in the direction of the bit of 

 flesh ; often the antennae are held for some time in the direc- 

 tion of the object. On bringing the flesh nearer, the animal 

 may be seen to adjust itself in the nest for a sudden spring, 

 and if the flesh is sufficiently near to be touched by the 

 antennules the amphipod makes a sudden dart from the nest, 

 seizes the object, and draws quickly back again, never letting 

 go its hold, however, of the nest. The animal as a rule readily 

 distinguishes between the contact of flesh and that of a body 

 not serviceable for food. Only rarely does touching the anten- 

 nule with a needle call the animal forth from the nest. It 

 may be deceived more often if, when excited by the presence 

 of meat near by, one of its antennules be touched with a 

 needle; then it may dart out towards the needle and even 

 seize it. But the animal responds much more surely, as I have 

 found by repeated experiments, when the antennules come in 



