254 



SCIENCE. 



[N. S. Vol. XVII. No. 424. 



the optic nerve which call for quick re- 

 flexes. 



Homology.— It follows, then, that the 

 cells of the torus longitudinalis constitute 

 a nidulus of cells of common function, 

 homologous with cells of similar function 

 which occur in the anterior dorsal portion 

 of the optic lobes of other vertebrates, and 

 which have been designated as the 'Dach- 

 kern, ' 'nucleus magnocellularis, ' etc. 



Phylogeny.— The nidulus of cells which 

 gives rise to Reissner's fiber and consti- 

 tutes the torus longitudinalis of teleosts 

 is one of the most archaic elements of the 

 vertebrate brain. As an independent 

 structure, however, the toriis has its begin- 

 nings in the ganoids, resulting from the 

 crowding downward of the nucleus mag- 

 nocellularis so as to form two incipient 

 longitudinal ridges on either side of the 

 median plane. In the Siluridas, mechan- 

 ical causes are still operative, but in the 

 more highly diflrerentiated teleosts the 

 torus appears at an early stage of onto- 

 genetic development as the result of phylo- 

 genetic causes. 



An U^i^isual Attitude of a Four-weeks 

 Human Embryo. Comparisons with the 

 Mouse: Susanna Phelps Gage, Ithaca, 

 N. Y. Illustrated by wax models. To 

 be published in the Journal of Anatomy. 

 .1. The specimen cut in the membranes 

 shows the body axis lying in two planes 

 at right angles to each other, the torsion 

 occurring in the neck region. The attitude 

 suggests: (a) that the great growth of the 

 heart and the umbilical region on the left 

 may have produced the torsion mechan- 

 ically; (6) that the pulsations of the heart 

 lave produced a passive rotation, or (c) 

 that the rapidly developing muscle cells 

 may already at this early stage have a 

 slight power to produce motion. 



2. A very early mouse embryo— that is, 

 with nine myotomes — shows a sharp bend 



in the region of the fourth to the sixth 

 myotome, that is, in the cervical region. 

 In the early human embryos so familiar 

 from His' illustrations which show a sim- 

 ilar shai'p bend and have by some been 

 considered as distorted, the bend occurs in 

 the region of the 12th to the 14th myotome, 

 that is in the dorsal region. In both these 

 human specimens and in the mouse in 

 which no manipulative distortion was pos- 

 sible, the common feature is that the bend 

 is over the opening of the yolk-sac. Rapid 

 growth of the myotomes together with 

 rapid narrowing of the neck of the yolk- 

 sac might in either case produce the con- 

 dition. 



The Cranial Nerves of Squalus aca^ithias: 

 Oliver S. Strong, Columbia University, 

 New York city. To be published in the 

 Jour7ial of Comparative Neurology. 

 The principal object of the research has 

 been to trace the components of the V., 

 VII., IX. and X. nerves. In doing this 

 special attention has been paid (a) to the 

 verification, by study of serial sections, of 

 the results obtained by Stannius, Ewart 

 and others by dissection of selachians ; viz., 

 that the canal and ampuUary organs are 

 solely innervated by certain special roots 

 and their branches (lateral line compo- 

 nent) ; (&) to the separation of the com- 

 munis (splanchnic-sensory and end-bud) 

 component, which has not hitherto been 

 done in selachians. 



In no case thus far in this research have 

 any branches of the V. nerve been traced 

 to canal or ampullary organs. These or- 

 gans in the head are innervated solely by 

 the two lateral line roots of the VII. nerve 

 which form the rami ophthalmicus super.- 

 ficialis VII., buecalis VII., mandibularis 

 externus VII. and certain minor branches. 

 The ramus mandibularis externus VII. is 

 apparently derived practically entirely 

 from the more dorsal of the two lateral 



