424 DAVIDSON BLACK 



tactic influences derived from two main sources, viz., the fas- 

 ciculus longitudinalis medialis and the arcuate fibers from the 

 overlying communis area. 



In addition to the evolution of a hypoglossal nucleus as an 

 individual cell group of the cervical motor column, there is 

 also evidence of intrinsic nuclear differentiation to be seen in 

 the arrangement of the oculomotor perikaryons. Here however 

 it is not possible to indicate as yet any individual fiber systems 

 by whose direct influence the cellular arrangement may be 

 determined, but as already noted, these changes are in all prob- 

 ability indirectly determined by the evolution of the amphibian 

 mechanism for accommodation. 



Finally it may be noted that such evidence as can be adduced 

 from the study of the cerebral motor nuclei in amphibians is in 

 accord with the conception of the derivation of these animals 

 from crossopterygian-like ancestors. 



LITERATURE CITED 



(1) BabXk, E. 1909 Ueber die Ontogenie des Atemzentrums der Anuren und 



seine automatische Tiitigkeit. Pfliiger's Arch., Bd. 127, pp. 481-506. 



(2) 1913 Die Mechanik und Innervation der Atmung. Handb. d. ver- 

 gleich. Physiol, herausg. v. H. Winterstein, Bd. 1, 2nd Halfte, Sect. 

 XV: Amphibien, pp. 706-810. 



(3) Babak, E. xjnd KtJHNOVA, M. 1909 Ueber den Atemrhythmus und die 



Ontogenie der Atembewegungen bei den Urbdelen. Pfliiger's Arch., 

 Bd. 130, pp. 444-476. 



(4) Baglioni, S. 1900 Der Atmungsmechanismus des Frosches. Arch. f. 



(Anat. u.) Physiol., Suppl. Bd., pp. 33-59. 



(5) 1911 Zur vergleichenden Physiologic der Atembewegungen der Wir- 

 beltiere. II. Teil, I. Amphibien. Ergeb. d. Physiol., Bd. 11, pp. 

 531-547. 



(6) Beer, T. 1893 Studien liber die Akkomodation des Vogelauges. Pfliiger's 



Arch., Bd. 53, pp. 175-237. 



(7) 1894 Die Akkomodation des Fischauges. Pfliiger's Arch., Bd. 58, 

 pp. 523-650. 



(8) 1898 Die Akkomodation des Auges bei den Reptilien. Pfliiger's 

 Arch., Bd. 69, pp. 507-568. 



(9) 1899 Die Akkomodation des Auges bei den Amphibien. Pfliiger's 

 Arch., Bd. 73, pp. 501-534. 



(10) Black, Davidson 1917 The motor nuclei of the cerebral nerves in phy- 

 logeny. A study of the phenomena of neurobiotaxis. Part I. Cyclo- 

 atomi and Pisces. Jour. Comp. Neur., vol. 27, no. 4, pp. 467-564. 



