1882.] 



On the Spectrum of Carbon. 



403 



were to continue to increase indefinitely, an organ resembling the 

 highly developed structure in the Mormyridse would result. This 

 latter then may be looked upon as homologising with, the valvula 

 cerebelli and its wings in the ordinary teleostean. 



With regard to the body which is placed behind the cerebellum, 

 the author points out that the Cyprinidre possess a well-known 

 tuberosity occupying a corresponding position, which is termed by 

 writers the tuberculum impar ; this, in conjunction with the vagal 

 tuberosities of the medulla oblongata, presents layers comparable to 

 those existing in the structure in question belonging to the Mormy- 

 ridos ; he therefore suggests that the homology of this exaggerated 

 tuberosity in these fishes is to be looked for in the tuberculum impar 

 together with the vagal tuberosities of the Cyprinida?, the increased 

 size in the former species having caused it to include the origin of 

 the trifacial in addition to that of the vagus. 



In conclusion, the author offers some criticism of the ideas lately 

 put forward by Fritsch* as to the homologies of the various parts of 

 the brain in fishes, the key to the whole of which lies in his interpre- 

 tation of the tecta lobi optici, which he takes to be the persistent 

 cortex of the primary anterior vesiclef of the brain of the embryo, and 

 consequently to belong to the thalamencephalon, and not to the- 

 mesencephalon. 



In reply to this the present writer points out that the homologies of 

 all the other parts of the brain in Teleostei may be deduced from the 

 position of the pineal gland, the infundibulum, and the ganglion of 

 origin of the oculomotorius. 



From this line of argument he maintains that the tecta lobi optici 

 correspond to the anterior pair of the corpora quadrigemina, and con- 

 sequently belong to the mesencephalon, and not to the thalamen- 

 cephalon. Finally he remarks that the brain in Teleostei would not be 

 in accordance with the remainder of their organisation, if all the 

 parts of a mammalian cerebrum could be distinguished in it, even in 

 a comparatively rudimentary state as is maintained by Fritsch. 



III. " On the Spectrum of Carbon." By G. D. LiYEiNG, M.A. r 

 F.R.S., Professor of Chemistry, and J. Dewar, M.A.,F.R.S., 

 Jacksonian Professor, University of Cambridge. Received 

 February 23, 1882. 



The spectroscopic investigations we have communicated to the 

 Society " On the Reversals of the Lines of Metallic Vapours," have 



* " TTnters. u. d. feineren Bau des Fischgehim." Berlin, 1878. 

 f " Priinares Vorderhirn," loc. cit. 



