No. 2.] LINE SYSTEM OF BATRACHUS TAW. 23 1 



nasal tube. This scale bears some resemblance to the carti- 

 laginous tube of the temporal canal, yet is unlike it, and seems 

 to be a peculiar structure found in no other part of the canal 

 system of Batrachus. Something very similar is found in the 

 canal of the trunk in Cottus gobio (Cut 2), 

 as described and figured by Bodenstein (9). 

 The nasal tube itself is a canal belong- 

 ing to this system which never becomes 

 surrounded by any bony formation. In cut 2. — .scaie from tmnt 

 this connection it may be stated that there ""^ ° °""''^° '"■ 

 is good reason for regarding the semicircular canals of the 

 ear as belonging to the lateral line system, although shut off 

 entirely from the surface of the body. This view has been 

 advocated by Ayers (10) and other writers. 



Number and Position of Organs. 



In Batrachus the organs in canals are identical with the 

 so-called free organs, the only difference being the fact that 

 the free organs, being situated on dermal papillae, have a 

 slightly different form. 



The number of organs on the head is 128, and on the body 

 140, making a total of 268 organs on the entire surface of the 

 head and body. The number enclosed in canals is only 30, 

 making the number of free organs 238. There is no indication 

 that the number of organs increases by multiplication during 

 the life of the fish, and the "nerve ridges " described by Allis 

 (2) have never been found in Batrachus. The " pit organs " of 

 Amia, assigned to the same general class of nerve hillocks, 

 are yet said to differ greatly from the canal organs in " shape, 

 arrangement, and methods of multiplication." From the 

 description, however, there seems little evidence of greater dif- 

 ference than between the enclosed and free organs of Batra- 

 chus, except, possibly, in the size. It seems quite impossible to 

 arrange them in two separate groups in the case of Batrachus, 

 as they replace so constantly the regular canal organs. The 

 enclosure of organs within a canal seems quite incidental and 

 secondary. The absence of accessory lines of pit organs is 



