CRANIAL NERVES OF CHIMERA MONSTROSA. 633 



described the hearing apparatus of a large number of fishes, and amongst them of 

 Chimsera. He was therefore the first to describe the important fact, that Chimsera 

 differs from all other cartilaginous fishes in that a portion of the internal ear projects 

 into the cranial cavity, and is not entirely enclosed by the auditory capsule — this con- 

 stituting an important point of resemblance between the sensory apparatus of Holo- 

 cephali and Teleostei. Breschet's work was followed in 1842 by a paper of Valentin's 

 on the brain (2), and this author committed the extraordinary error of completely 

 overlooking the thalamencephalon, together with the cerebral hemispheres and olfactory 

 lobes, and described the former — which, as is well known, is drawn out and band-like in 

 character — as the olfactory nerve. In the following year Johannes Muller and 

 R. Wagner* (3) published a criticism of Valentin's paper, doubting the homologies of 

 some of the parts, but although Muller made a re-examination of the brain, he did 

 not succeed in detecting the error mentioned above. This, however, was done in 1848 

 by Busch (5), whose somewhat inaccessible memoir, therefore, was the first accurate 

 account of the gross anatomy of the Holocephalan brain to be published. Busch figured 

 (Plate II. figs. 7, 8, and 9), and described (pp. 35-40) Callorhynchus as well as Chimsera, 

 and one of his figures of the latter may be seen in Owen's text book.t Stannius 

 followed in 1849 with his epoch-marking work on the peripheral nervous system of 

 fishes (6), and here we get the first account of the cranial nerves of Chimsera. This 

 important study will be discussed later on, and it is only necessary to say here, that 

 owing partly to the absence of any embryological data, and partly to an insufficient 

 examination of the intra-cranial portions of the nerves, Stannius fell into serious errors, 

 which, in spite of recent work on the subject, are being perpetuated even now. An 

 admirable account of the advancement that had been made up to 1854, both as regards 

 Chimsera and cranial nerves generally, is given by Stannius in his Handbuch (8), 

 which, although it contains no new facts of importance, is still an interesting and 

 valuable addition to the literature of the subject.^ The next memoir demanding 

 attention was published in 1851 by Leydig (7), who had investigated the anatomy of 

 the sensory canals, and showed that the canals of the anterior extremity were inter- 

 mediate between the posterior open canals and the closed canals of Callorhynchus, in 

 that they were partially closed by means of imperfect rings of calcified cartilage, which 

 brought about an approximation of the lips. He also described and figured what I 

 shall hereafter refer to as the compound ampullae of the sensory apparatus, and made 

 some further observations on the ear. Mayer next attacked the brain in 1864 (10), 

 and engages upon a somewhat lengthy discussion of Chimsera, but does not add anything 



* Muller refers to observations of Wagner's, which were either of a personal character only, or for some reason 

 or other were never published. 



t Anatomy of Vertebrates, vol. i. p. 276, 1866. 



% Several works appeared at about this time (e.g.,l>j Prince Bonaparte, 1846 ; Costa, 1852 ; andDuM^RiL, 1865), 

 in which the geography of the sensory canals of Chimcera was figured and described ; but it is not necessary to refer to 

 them specially, since, as far as Chimcera is concerned, they contain little that is new and nothing of importance. 

 Ddm^ril gives a rough description of the ear, apparently unaware that this had previously been described by 

 Breschet (1). 



