402 Edward Phelps AUis jr., 



fully as my personal library will permit; to carefully reexamine, and 

 to control as far as possible, a number of sketches made from five 

 to seventeen years ago, in connection with other work I was engaged 

 on; and to supplement the facts thus arrived at by the study of se- 

 veral new fishes. 



In this latter part of the work I have had the help of my pre- 

 sent assistants Messrs. Jujiro Nomura, Geo. E. Nicholls, and John 

 Henry, to whom the preparation and dissection of the material has 

 been wholly confided. The earlier sketches, and the dissections rela- 

 ting to them, were all made by Mr. Nomura, excepting those relating 

 to Perca, which were made by Dr. J. Dewitz, and those relating to Esox 

 and Silurus, which were made in part by one and in part by others of 

 several assistants I have had from time to time in my laboratory here. 



It is, I believe, generally accepted that certain of the cranial 

 bones of fishes are usually developed in some sort of direct relation 

 to the latero-sensory canals; and that a component part of certain 

 other bones may also be so developed. This latero-sensory component 

 of these latter bones apparently always is, in principle, and certainly 

 often is actually, first developed wholly independent of a subjacent 

 membrane or perichondrial component, one or both, and it may or 

 may not later fuse with that component. This has all been already 

 more or less fully stated by several authors, among them myself [3], and 

 has lately received further confirmation by Schleip's [66] work on Salmo. 



These latero-sensory bones, oi' components, usually each lodge at 

 least one latero-sensory organ; but sections of the latero-sensory ca- 

 nals that contain no sense organ, may be partly or even entirely en- 

 closed in certain of the cranial bones, or even in independent tubular 

 ossicles. This is seen in the bones that enclose the frontal, post- 

 frontal, and posttemporal sections of the main infraorbital canal of 

 Cole's descriptions of Gadus [26]-, in the postfrontal bone, the 7th. 

 suborbital ossicle and the two or more supratemporal ossicles of 

 Herrick's descriptions of Ameiurus [47]] in certain of the supratem- 

 poral ossicles, and probably also in the sphenotic bone of Cole and 

 Johnstone's descriptions of Pleuronectes [27]] and in my own descrip- 

 tions [.9 1 of the }»ost-squamosal section of the main infraorbital canal 



