MOTOR NUCLEI IN PHYLOGENY 



77 



In Anolis Willard notes that the trochlear nucleus and the 

 whole central course of its root may be seen in a single transverse 

 section (1. c, p. 45). The relations of the oculomotor root and 

 nucleus are not so evident from his description, but it would ap- 

 pear that most of the nucleus is situated on the level of its 

 emergent root. This being so, on reference to Willard's recon- 

 struction (1. c, pi. 2, fig. 4), the fact emerges that a considerable 





'T)ec.te<i-^ori 



Fig. 9 Damonia subtrijuga. Transverse section through the brain stem at 

 the level of the oculomotor root exit. Abbreviations: G. i. p., ganglion inter- 

 pedunculare; Lam. op., afferent optic fibers to tectum; Lam. prof., deep medul- 

 lated lamina of tectum; A^. IIL, oculomotor nerve; Nu. III., nucleus oculomo- 

 torius; Nu. V. mes., cells of mesencephalic nucleus of trigeminus; Tr. II . ., tractus 

 opticus; Tr. t. b. dors, cruc, arcuate bundles of the tractus tecto-bulbaris dorsalis 

 cruciatus passing ventromediad through scattered bundles of the tractus tecto- 

 bulbaris non-cruciatus to decussate; Tr. t. b. vent., ventrolateral system of tecto- 

 bulbar fibers before decussation; Vent, op., optocoele. Other abbreviations as 

 before. 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 32, NO. 1 



