Animal life and intelligence . estimates the number to be39,000. In the aquatic crayfish thereare, besides the long antennae,smaller antennules, each ofwhich has two filaments, aninner and an outer. On theunder surface of most of thejoints of the outer filamentthere are two bunches ofminute, curiously flattened or- „„„„ „,!,• -U „, ill Fig. 26.—Antennule of crayfish. gans, which were regarded by .. J Z. . ° J 1-3-, mner joint; , outer joint; ol., Ley dig, their disCOVerer, aS olfaotory setEe; ol., the same, enlarged; , auditory opening in the basal di- olfactory. Observation, too vis
Animal life and intelligence . estimates the number to be39,000. In the aquatic crayfish thereare, besides the long antennae,smaller antennules, each ofwhich has two filaments, aninner and an outer. On theunder surface of most of thejoints of the outer filamentthere are two bunches ofminute, curiously flattened or- „„„„ „,!,• -U „, ill Fig. 26.—Antennule of crayfish. gans, which were regarded by .. J Z. . ° J 1-3-, mner joint; , outer joint; ol., Ley dig, their disCOVerer, aS olfaotory setEe; ol., the same, enlarged; , auditory opening in the basal di- olfactory. Observation, too vision> wbich has been cut °pen to show , the auditory sac; , auditory seems to confirm the view that nervebranohinstothetworidsesbesetwith auditory hairs; , auditory hair, en- the sense of smell (or telaes- larged- (After Howes-)thetic taste) is located in the antennule. I tried on acrayfish the following experiment: When it was at restat the bottom of its tank, I allowed a current of pure. 260 Animal Life and Intelligence. water (the water in which it lived) to flow from a pipetteover its antennae and antennules. The antennas movedslowly, but the antennules remained motionless. I thentook some water in which a cods head had been boiled,and allowed some of this to stream over the antennas andantennules. The former moved slightly as before, but theantennules were thrown into a rapid up-and-down jerkyvibration, and shortly afterwards the crayfish began movingabout the bottom of its tank. If only one antennule bethus stimulated, or stimulated to a higher degree than theother, the crayfish seems generally (but not always) toturn to that side in search of food. Mr. Bateson * hasshown to how large an extent shrimps and prawns seek theirfood by smell, and states that a prawn, though blind, willoften find his way back to his proper place, and stay in the snail the anterior pair of horns, or tentacles,are said to be olfactory. Near the end of each
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