Aug. 24, 1888.] 



SCIENTIFIC NEWS. 



179 



Natural litetora)* 



THE SENSES OF INSECTS. 



I. Preliminary. 



The manner in which, throughout animated nature, the 

 nervous system deteriorates, so to speak, by slow but 

 sure degrees as we pass downwards in the scale, cannot 



Then, as we work our way from mammals to birds, birds 

 to reptiles, reptiles to fishes, and fishes to invertebrates, 

 each descending step shows us a corresponding deteriora- 

 tion, until in some of the lower forms of life we fail to 

 discover any traces of a nervous system at all. 



Especially do we find this to be the case with the 

 brain. In man, of course, that organ is quite unique in 

 character, greatly excelling in comparative bulk, and still 

 more in quality, that of any other animal, But putting 



Nervous System of Bee. 



fail to have greatly struck all those who have enrolled 

 themselves as workers in the field of comparative anatomy. 

 This system attains, of course, its highest perfection 

 in man, whose intellectual requirements have to be pro- 

 vided for as well as those mental and physical needs 

 which he possesses in common with many of the lower 

 animals, while that same intellect endows him with 

 special capacities for the appreciation of pleasure and 

 pain, which in their turn also imply an unusual com- 

 pleteness in the development of the nervous system. 



man altogether upon one side, una taking the monkey 

 type as the most physiologically perfect, we may trace 

 the gradual degradation of the brain even in the mam- 

 mals, which degradation, becoming still more marked in 

 the birds, the reptiles, and the fish, ends in the apparently 

 complete effacement of the organ in question in that 

 most singular creature the Amphioxus, which seems to be 

 a link between the vertebrates and the invertebrates, con- 

 necting the two great classes together. 



In the molluscs, however, which stand foremost in the 



