424 H. p. KJERSCHOW AGERSBORG 



Copeland on this point. He finds that the ' rhinophores' of 

 Chromodoris elegans and C. zebra have nothing in connection 

 with olfaction. Alder and Hancock, Hancock and Embleton, 

 JefTrej^s, Tapparone-Canefri, Bergh, Fischer, et al., based their 

 opinion, relative to the function of the dorsal tentacles, on 

 morphological data. The findings of Arey are somewhat in 

 agreement with my own observations (vide infra). And, as 

 we will see, it may not be well to designate a specific function to 

 these organs, even though their response may be similar to that 

 of vertebrates with definite localized and known sense organs 

 relative to their specific function. Thus, even though the so- 

 called rhinophorium is highly innervated with nerves from the 

 anterior part of the brain (Hancock and Embleton), it may not 

 be a good criterion at all by which to judge its function, for the 

 simple reason that the brain of invertebrates is not analogous 

 to the brain of vertebrates. In fact, Minnich ('21) has shown 

 that the organs of taste in the butterflies Pyrameis atalanta 

 Linnaeus and Vanessa antiopa Linnaeus are located in the tarsi. 

 He demonstrated that tarsal chemoreceptors are present in all 

 four tarsi of the walking legs. The removal of the antennae 

 labial palpi, and rudimentary fore legs in Pyrameis does not 

 affect in any significant way the responses produced through 

 contact chemical stimulation of the tarsi. From the anatomy 

 of Lepidoptera it is seen that the pedal nerves are innervated 

 from the thoracic ganglia, and not from the brain. Chemo- 

 receptors, according to Minnich, may be divided into two classes : 

 first, those affected in general by volatile materials, the source of 

 which may be more or less remote from the receptive surface; 

 second, those affected in general by non-volatile materials, the 

 source of which must be in intimate contact with the receptive 

 surface. The former serve as distance chemoreceptors; the 

 latter, as contact chemoreceptors. The above distinction, how- 

 ever, is far from being an absolute one, but is merely useful as 

 the best single condition by which the two groups of sense organs 

 may be conveniently differentiated. For, it is contended, in 

 the last analysis both are stimulated by a solution of the exciting 

 material, the solvent consisting, at least in part, of the secretion 

 present on the sensitive surface. 



