2 Journal of Comparative Neurology. 



last task is far from complete ; however, pending the time when 

 results in this difficult field may be gained of sufficient definite- 

 ness and coherence to render their publication of value, a more 

 general consideration of the dorsal portions of the oblongata in 

 fishes may serve to emphasize the regions whose various modi- 

 fications have produced the truly enormous structures of cer- 

 tain teleosts, namely; — (i) the center of the acoustic and lat- 

 eral line system nerves; (2) that portion which is the undoubt- 

 ed representative of the fasciculus communis portion of the 

 Amphibian oblongata ; and (3) the spinal fifth tract, the direct 

 continuation of the dorsal columns of the myel. These are 

 three systems having constant relations to certain cranial nerves, 

 and should have names indicative of their character. It seems 

 unwise, however, to introduce new terms. They will be spoken 

 of as the ( Systeina ) acusticum, the fasciculus communis or ( fas- 

 ciculus ) communis system and the spinal Vth ( fifth ) tract, re- 

 spectively. 



The forms considered here^ comprise 17 species, represent- 

 ing among the teleosts 10 families and 5 orders. Although far 

 too few to permit any general conclusions being safely drawn 

 as to the characteristic development in the various orders or 

 even families, they yet strongly suggest what may be the case, 

 and have given a far better idea of the extent and significance 

 of the modifications of the regions. 



This study was conducted by means of serial sections made 

 through this region of the brain. Where but a single series 

 was made the sections were transverse ; in some cases supple- 

 mentary series were made in the other two planes. The brains 

 were fixed in Fish's picro-aceto-sublimate (formula: picric acid, 

 I gram ; mercuric chloride, 5 grams; glacial acetic acid, 10 

 c.c; 50% alcohol, 1000 c.c.) or vom Rath's picric-sublimate- 

 acetic mixture (formula: picric acid, sat. aq. sol. 100 c.c, hot 

 sat. sol. mercuric chloride 100 c.c, glacial acetic acid. 2 c.c.) 



' Namely, Anita calva, Lepidosteus ossetis, Acipenser rubicundus, Amiurus 

 nebulosus, Catostomiis teres, Notemigomis chrysoleucus, Exoglossum maxillilingua, 

 Notropis cornuttis, Cyprinus carpio, Clupea pseudoliarengea, Esox reticulatus, Coi- 

 tus ictalops, Perca Jlavescens, Lepomis gibbosus, Roccus chrysops, Fundulus 

 diaphanus. 



