Literary Notices. clxxi 



The Morphological and Histological Development of the Cerebellum of 

 Teleosts. 1 



This important paper presents the details of an investigation ex- 

 tending through several years upon the salmon and trout. The cere- 

 bellum of teleosts develops from a bilaterally symmetrical anlag which 

 at first is produced by a sharp transverse fold at the lateral aspects of 

 the nerve-tube between the vesicles of the mesencephalon and med- 

 ulla. The subsequent growth is from below upwards toward the me- 

 dian line in the caudal limb of this fold. Two thickened columns 

 are thus formed which constitute the anlag of the future cerebellum, 

 while a secondary median fold arising later develops into the valvula 

 cerebelli. The ventricular space between the two lateral columns ex- 

 pands above into a " cavum cerebelli primitivum," while below it is 

 quite obliterated by the subsequent thickening of the pillars. A cen- 

 tral canal in the sense of earlier authors does not exist in most fishes. 



In the discussion of the histological development the author 

 brings forward many points of interest to the morphologist. The 

 teachings of His regarding the relation between the neuroblasts and 

 spongioblasts are controverted. It is claimed that a fundamental dis- 

 tinction between the germinal cells and the epithelial cells (in the sense 

 of His 2 ) does not exist. The elements called germinal cells by His 

 are nothing but young or segmenting epithelial cells of the primitive 

 ectodermal anlag. From a certain point of time onward, these germ- 

 inal cells give rise no longer to epithelial cells, but to a generation of 

 indifferent cells, which wander peripherally to take up a position be- 

 tween the epithelial cells and the membrana limitans externa (mantel 

 zone). From these indifferent cells there arise later both nerve cells 

 and glia cells. With the increasing differentiation of the cerebellum 

 a certain number of indifferent cells do not undergo metamorphosis. 

 They can multiply by karyokinesis and thus furnish the material re- 

 quired for the nerve cells and glia cells of the other structures. Prob- 

 ably the capacity for subsequent regeneration in the central nervous 

 system is to be referred to the persistence of some of these indifferent 

 cells. The whole neuroglia frame-work of the cerebellum is ontoge. 

 netically to be referred to the indifferent cells and that part of the 

 primitive epithelial cells of the medullary tube which persists as epen- 



'Schaper, A. Die Morphologische und Histologische Entwicklung des 

 Kleinhirns der Teleostier. Morpholog. Jahrbuck., XXI, 4, 1894; also a Pre- 

 liminary Contribution in Anat. Anz., IX, 16, June, 1894. 



2 Cf. the review in this Journal, Vol. I, pp. i-iv. 



