No. 2.] LINE SYSTEM OF BATRACHUS TAU. 237 



General Considerations. 



If one may judge from the contributions to this subject by 

 various investigators, it is becoming evident that the lateral 

 line system may take rank among the organs of special sense. 



The connection of the olfactory, optic, and auditory organs 

 with the central nervous system is effected by means of special 

 pairs of cranial nerves originating in definite centers within the 

 brain. On the other hand, the sensations of touch are medi- 

 ated by cutaneous nerves which seem to be so universally dis- 

 tributed as to suggest the idea that the skin itself may be 

 regarded as an immense sense organ and its innervation corre- 

 spondingly general. 



The system of the lateral line has usually been regarded as 

 composed of organs of the more generalized type. Their wide 

 distribution over the entire head and body would favor this 

 conclusion, but the study of the cranial nerves of Amphibia 

 brings into view several significant facts. In his recent paper, 

 Strong (11) calls attention to a "most beautiful extirpation 

 experiment in nature." The tadpole has the sense organs 

 found in fishes and the Urodeles, and these organs are inner- 

 vated by certain dorsal branches of the cranial nerves. When 

 the tadpole becomes a frog, and these organs disappear from 

 the skin, the dorsal branches supplying them become atrophied. 

 As regards the innervation of the lateral line organs, there 

 seems to be a remarkable agreement between the Urodela, larval 

 forms of Anura, and the fishes. In general, the arrangement 

 seems to be the same, inasmuch as dorsal branches of the VII 

 and X cranial nerves supply these organs. This has been 

 shown in the case of amphibians (11), selachians (12), two 

 ganoids and one dipnoid (13), but among teleosts the mat- 

 ter has been in doubt. Batrachus is certainly one teleost in 

 which the dorsal branches are present and innervate the lateral 

 line organs. 



In his analysis of the cranial nerves of Amphibia, Strong 

 gives a description of the different nerve components distin- 

 guishable by the nature of their fibres, peripheral distribution, 

 and internal origin. 



