clxxiv Journal of Comparative Neurology, 



After an historical resume, which gives a brief statement of the 

 most important theories and observations, the author discusses the 

 morphological problems which are abundantly suggested by this diffi- 

 cult region. 



Like nearly all authors, David considers the lobi as evaginations 

 of the third ventricle with which their own ventricles communicate. 

 He recognizes the recessi which Herrick first described and homolo- 

 gized with the mammillaria. The homology he is unwilling to ac- 

 cept, objecting, in the first place, because of the absence of nuclei 

 and, in the second, because of their ventral position, and, finally, 

 because of the irregularity of occurence. Herrick, however, states 

 that he never fails to find indications of it in a much wider range of 

 observation and recognizes cellular contents within and about the or- 

 gan. Herrick also finds the region in amphibians and reptiles. 



From a series of comparative measurements no general conclus- 

 ions proved educable. The histological portion contains the results 

 of Golgi impregnations and Weigert preparations ; the results being 

 quite similar to those printed in this journal, May, 1892. Histoge- 

 netic conclusions are drawn for which our readers will not be entirely 

 unprepared. 



"The axis-cylinder of the older cortex cells of the lobi inf. 

 which are derived from the epithelial layer, are at first radiately dis- 

 posed, and subsequently, in the course of further development and 

 changes in the position of the cell-bodies are turned transversely. In 

 fact we might conceive of the change of position as a natural and 

 necessary mechanical result of the migration of the cortical cells from 

 the epithelial layer." Precisely similar suppositions have been made 

 with respect to the cerebral cortex. 



Under the discussion of the adjacent niduli the observations of 

 Herrick are verified and new details added. It is noted that the 

 blood-vessels of the "rotundus" (ruber) are largely derived from the 

 saddle cleft, a fact fitting well with the homology with the ruber as 

 also the fact that a part of the dorsal-longitudinal fasciculus ends there. 



David is inclined to homologize the dorsal peduncles with Eding- 

 er's " mantle bundle." We find no evidence that the author succeeded 

 in finding the embryonic origin of the ruber from a ventricular layer, 

 but in general the results favor the hypothesis of His. 



While the paper before us does not say the last word on the 

 hypoaria, it is sufficient to produce an attitude of expectancy for the 

 work which may follow it. 



