n8 Journal of Comparative Neurology 



but imperfectly made out, have not prevented the publication of 

 certain psycho-genetic conclusions. But although there are 

 many questions which arise in this study which seem as far as 

 ever from an adequate answer, yet there are other questions 

 which seem to require but persistent and thorough investigation 

 to yield fruitful results. Perhaps this is not more true of the 

 olfactory organs than of others, but certainly there is evidence 

 of a simpler functioning than is the case in the eye and ear at 

 least, whether the organs themselves are correspondingly more 

 simple in structure or not. 



Smell is one of the earliest senses phylogenetically. Hints 

 of such a sense are found in the function of the processes and 

 antennae found in many invertebrates, {star-fish, insects, etc.) 

 Ants communicate by means of their antennae, and the fact that 

 recognition is prevented by immersion in water, along with other 

 experiments, suggests that such recognition is largely at least 

 due to olfaction. An ant immersed as above described is im- 

 mediately set upon and destroyed by its fellows, comrades in 

 the same colony, after a short examination of the victim by 

 means of those infallible sense-bearing feelers. The explanation 

 is that the peculiar odor characteristic of each member of a given 

 colony is lost by this submersion of the ant. The supra-cesoph- 

 agal ganglia found in some types are supposed to be not a 

 "brain" as often described but a mass of sensory organs 

 among which is a more or less highly differentiated proton of an 

 olfactory apparatus. This reference, however fanciful and per- 

 haps unreliable, may assist in homologizing invertebrates in this 

 respect with higher forms. 



i. Perhaps the most probable theory as to the origin of the 

 primitive olfactory epithelium sacs is that which postulates their 

 origin from the lateral line system. This theory is supported by 

 such authors as Beard, who is very explicit on this point. He 

 says: "The nose and ear are in the same category of sense- 

 organs as those of the lateral line (the branchial sense-organs), 

 a system of sense-organs which vertebrates have inherited from 

 their annelidan ancestors. The power to evolve new sense-or- 

 gans from indifferent foundations must be absolutely refused 



