xxviii Journal of Comparative Neurology. 



ablest researches in morphology and especially in embryology between 

 the cranial and the spinal nerves are futile because their authors have 

 attempted to homologize disparate structures. The lateral line nerves 

 especially must be rigidly excluded from all such comparisons, for 

 this is the component whose independence has been most conclusively 

 demonstrated. 



Dr. Fiirbringer has traced the connection between the caudal, or 

 ascending, motor root of the vagus and the trapezius muscle, and 

 thus verifies the supposition that this root represents the accessorius 

 Willisii. He controverts the view of Stohr, Wiedersheim and others 

 that this nerve is a descendant of the spinal nerves, and argues that 

 the vago-acressorius is a unit and a primordial cranial nerve. Its 

 central relations certainly favor this view, yet peripherally there are 

 several points of difficulty, even if we were to accept, as Dr. Fiirbringer 

 does, Gegenbaur's theory of the origin of fins from gill arches. 

 The comparative anatomy of both the m. trapezius and the ven- 

 tral musculature between the pectoral arch and the gill arches (cleido- 

 branchialis, Fiirbringer ; Paryngo-clavicularis, Vetter) is by no means 

 satisfactorily settled. For example, in the bony fishes Fiirbringer re- 

 gards the m. cleido-branchialis as innervated from the occipito-spinal 

 nerves and the m. trapezius from the vagus. But McMurrich de- 

 scribes both muscles in Amiurus as innervated from the spinals, Vet- 

 ter gives instances in which the trapezius is innervated by the spinals 

 and the cleido branchialis by the vagus, and the present writer can 

 vouch for one case where both muscles are supplied by the vagus. 



In some of these cases it is difficult, if not impossible, to decide 

 these questions with the scalpel and we must resort either to electrical 

 stimulation of fresh material or to reconstruction from serial sections. 

 It is not impossible that several of these cases may occur among the 

 bony fishes. Such a fact, if it be a fact, would suggest a series of 

 most interesting morphological problems. 



The reduction from before backward, which was observed in the 

 spino-occipital nerves of the Ichthyopsida, continues progressively as 

 we ascend the taxonomic series, so that the general rule may be laid 

 down that among the adults of almost every class of vertebrates the 

 more primitive forms are characterized by more, the higher forms by 

 fewer, of the spino-occipital nerves. The embryology in most cases 

 where it is known recapitulates more or less completely the steps in 

 this reduction. The higher mammals have lost from five to six of the 

 first spinal metameres, as compared with the lower selachians. 



The motive for this forward movement of the somatic metameres 



