1 68 STRONG. [Vol. X. 



After stating that stimulation had shown some of these roots 

 to be motor and the difficulty of distinguishing them in embryo- 

 logical stages, Goronowitsch lays down the following criteria of 

 a complete spinal nerve : — 



(i) The dorsal and ventral roots have different internal 

 origins. 



(2) It arises with two roots, a fine-fibred dorsal and a coarse- 

 fibred ventral. 



(3) It possesses a ganglion; 



It is further remarked by him that the distinction as to thick- 

 ness of fibre is not very essential. 



I may offer the following criticism. These three criteria 

 appear to me hardly sufficient, — the dorsal root should be a 

 ganglionated sensory (afferent) root and the ventral root a 

 non-ganglionated motor (efferent) root. Now in respect to 

 the Facialis and Trigeminus I, the ventral roots spring, con- 

 sistently, from a bundle (or from ventral cells) which, there is 

 every reason to believe, is efferent. This is not the case, how- 

 ever, with the ventral root of Trigeminus II derived from the 

 dorso-lateral tract. The two other nerves arising from this 

 tract, the Acusticus and Lateralis are sensory and the ventral 

 root in question even derives a few of its fibres from the cell 

 group likewise giving origin to a portion of the Acusticus. 



My criticism is not especially directed against Goronowitsch's 

 views on the relation between cranial and spinal nerves, but 

 simply to show, from his own observations, that there is no 

 sufficient reason for supposing that the ventral root of Tri- 

 geminus II is motor ; and thereby to remove, in advance, a 

 possible objection to the homology which I advocate, namely, 

 that Goronowitsch's "ventral root of Trigeminus II" in Aci- 

 penser is the same as the one described in the tadpole as the 

 dorsal VII, and that it and the N. lineae lateralis together 

 compose the lateral line system. The character of the fibres 

 and their similar internal origin both point to this homology 

 and, as will be seen below, so probably does their distribution. 

 Moreover, Stannius did not find these roots to be motor. 



The above being true, the question naturally arises : what is 

 the homologue in Amphibia of the lobus trigemini .'* At first 



