xxiv Journal of Comparative Neurology. 



The ventral nidulus forms a triangle the Ijase of which rests upon the 

 lamina meduUaris interna. Between the latero cephalic nidulus and the 

 corpus geniculatum externum lies the caudo-lateral nidulus. 



In the ganglion habenulte there is a lateral and median nidulus. 

 Between the two lateral niduli and the ganglion habenulse lie the lateral 

 and meso-caudal niduli. The corpus geniculatum externum consists of a 

 dor.sal nidulus with a distinguishable dorso-lateral portion. The ventral 

 nidulus of the corpus geniculatum may be separated into a ventro-mesal 

 and a ventre lateral portion. 



PR^COiMMISSURA. 



Rabl Riickhard 1 in a mature foetus of Xenuriis gyinnurus discovered 

 a strong tract from the anterior capsule to the external capsule. 



Torus Longitl'dinalis. 



Rabl- Riickhard identifies a longitudinal ridge from the ependyma of 

 the Sylvian aqueduct of Xenurus (Edentata) as the homologue of the torus 

 longitudinalis of fishes. 



Neuroglia. 



According to Weigert, the neuroglia fibres form a dense reticulum 

 upon the surface of the central nervous system. In the cerebrum the 

 reticulum is present in the white matter and superficial layer, while the 

 deeper parts of the cortex are comparatively poor in neuroglia fibres. 



Lachi states that in the chick up to the 8th or gth day there is an 

 ectodermal neuroglia (of spongioblast origin) but mesodermal elements 

 then appear forming the pia and sinking into the white substance. These 

 gradually reproduce and take the place of the spongioblasts. After birth 

 leucocytes and endothelium cells are superadded. Staderini states that 

 the granular substance found by Thompson at the exit of various cerebral 

 nerves and which Thompson regarded as degenerate nerve cells are easily 

 recognized in the 3d, 4th, 6th, 7th and loth nerves but really consist of 

 projections of the central neuroglia with which they retain connection. 



Microcephalic Deformity. 



The past twenty months have exhibited a great deal of progress in 

 the study of these interesting modifications. 



1. Einiges Mct>cr dasrichini (Icr Kdeiitata. Arcliiv f. iiiikr. Anatomic, XXXV. 

 1890. 



