116 MB. F. J. COLE ON THE STRUCTURE AND MORPHOLOGY OF 



A. Introduction. 



1 HIS investigation was first suggested to me as a desirable study by my former teacher, 

 Professor J. C. Ewart, F.R.S., some years ago. I had at the time contemplated worknig 

 at a Pleuronectid fish^ — allured by the problems which the asymmetrical head affords ; 

 but it was pointed out that I should be better equipped for such difficult work were I to 

 study a modern symmetrical Teleostean first, and that in fact it were almost an impossi- 

 bility to understand the former without having first investigated the latter. I therefore 

 abandoned my first project, and decided to work out the anatomy of the lateral line 

 system and its nerves on the common Codfish. That this work was necessary, and 

 indeed essential to the proper understanding of this complicated system, is very obvious 

 from a perusal of the literature. In spite of the enormous bulk of the latter, and the 

 ponderous theses and memoirs tlmt have been written on the subject of the present 

 communication, we still know very little about the fine anatomy of the lateral line 

 system, and very few authors have taken the trouble to grapple with the literature and 

 to conduct their investigations on a strictly logical and scientific basis. To Mr. Edward 

 Phelps Allis, who must be regarded as the pioneer in this work, vertebrate morphology 

 owes much. He was not only the first to make a comjilete study of the topographical 

 development of the lateral canals, and to give a correct and detailed account of their 

 innervation, but many important morphological deductions have been directly inspii-ed 

 by his work. This author has recently completed his work on Jmia. It is a completion 

 upon which I may be permitted to cordially congratulate the author, and to express the 

 hope that he will continue on other forms the studies he has pvn-sued with such 

 conspicuous success on Amia. Ewart has followed Allis with an account of his skilled 

 dissections of the very complex lateral line system of Lcemargus and Rata, and Pollard 

 has added some details on the ancient Siluroid Teleosteans. Pinkus has very largely 

 filled in a gap by an able account of the nerves of Protoptertis, and the writer has 

 published a description of the system in Chimcera. The most pressing want, therefore, 

 was an investigation of the details in a modern specialised Teleostean, and the pi-esent 

 memoir is largely an attempt to supply this deficiency in our knowledge of this 

 interesting apparatus in Gadus. 



The experience gained whilst working under Professor Ewart, and afterwards in 

 investigating Chimcera, has been most valuable in the interpretation of the nerves of 

 the Codfish. That the skeleton of this creature represents a very specialised condition 

 is a palaeontological fact, and it is hence not surprising to find its nerves in an equally 

 advanced stage. My previous work on the simpler cartilaginous fishes (most of which 

 has yet to be published) has prevented me from going astray in the interpretation of the 

 nerves, and has enabled me to see in the specialised Cod the disguised form of the 

 primitive cartilaginous fish. The separation of the components in the Cod has necessarily 

 been effected with the microscope, and one cannot urge too strongly the importance of 

 this instrument in the elucidation of cranial nerve morphology. Investigations based 

 solely on microscopic or naked-eye anatomy olten contain gross but pardonable errors ; 

 and whilst, on the other hand, a combination of the two methods docs not indeed remove 



