The Senses of Animals. 



297 



period than that which affects the human eye, their limits 

 do not very far exceed ours. We have seen that human 

 beings differ not a little in their limits of violet-sus- 

 ceptibility. "We may presume that Sir John Lubbock 

 and those who assisted him in these experiments were 

 normal in this respect. But it is possible that some indi- 

 viduals could have perceived a faint purple where there 

 was darkness to them, and that the majority of the 261 

 daphnias were collected in the region just beyond the 

 partition between ultra-violet and darkened violet. Still, 

 there is no cause for doubting the general conclusion that 

 daphnias are sensible to ultra-violet rays beyond the limits 

 of human vision. 



Sir John Lubbock has an interesting chapter on pro- 

 blematical organs of sense. In the antennae of ants and 



Fig. 40. — Antennary structures of hymenoptera. (After Lubbock.) 



a., cuticle; b., hypodprmis; c, ordinary hair; d., tactile hair; e., cone; /., depressed 

 hair lying over g. cup with rudimentary hair at the .base; h., simple cup; i., champagne- 

 cork-like organ of Forel; k., flask-like organ ; I., papilla, with a rudimentary hair at the apex. 



bees there are modified hairs and pits in the integument 

 (at least eight different types, according to Sir John 

 Lubbock), the sensory nature of which is undoubted. But 

 what the sensory nature in each case may be is more or 

 less problematical. Many worms have sense-hairs or 

 bristles of the use of which we are ignorant. Some organs 



