114 Dr. E. Schuster. Cell Lamination of the [Sept. 30, 



that the sections were somewhat erratic in their behaviour towards the 

 stain, and required a prolonged immersion in it. The preservation 

 of the cells was not sufficiently good to justify any minute histological 

 •description, and therefore none such has been attempted, nor' has the large 

 variety of cell outlines been described. A great deal of this apparent 

 diversity must be due to the cutting of similar cells in slightly different 

 planes, and to the many aspects which cells of the same type must present 

 to the observer according as they are placed in this position or that. 

 Moreover, it was felt that the drawings (figs. 3, 4, 5, 6) in which the cells 

 are represented in silhouette display both their shape and their arrangement 

 more clearly and more briefly than could any verbal description. 



Owing to the general shape of the hemisphere and, more particularly in 

 its posterior part, to the course of the fissures, transverse sections in the 

 neighbourliood of the two extremities are confusing on account of the 

 obliquity with which the cortex is cut. In order to obviate this difficulty 

 sections were cut from the left hemisphere in such a way that they 

 met the fissures as much as possible at -right angles. In spite of this 

 it has not been found possible to give any adequate presentment of the 

 cortex at the anterior and posterior extremities of the brain, but it is 

 hoped to obtain fresh material with which the gaps in the present paper may 

 be filled up, 



Ziehen* gives descriptions of certain types of cortex to be found in the 

 brain of Echidna but no figures either of the cell lamination or to explain 

 in what part of the hemisphere the structures he describes may be found. 

 As I could not from his verbal descriptions get any clear notion on the 

 latter point, I have omitted to compare his descriptions with my own. 



Surface Anatomy of the Brain {vide fig. 1). 



Before beginning a study of the transverse sections, in order tliat tliese 

 may be understood, it may be as well to say something of the arrangement 

 of the fissures. . The latter liave been described by G. Elliot Smithf and by 

 Ziehen.^ The descriptions agree in all essentials, but whereas Elliot Smith 

 designates the different fissures by letters of the Greek alphabet, Ziehen 

 provides them witli long Latin names indicating their positions on the brain. 



* " Das Contral-Nerven-Systeni der Moii()tr(;uion iiiul MarHupialor," 2. Tlieil, Micro- 

 HcopiHclu! Aiiatoniie ; 'Jenaische Deiikschr.,' VI, 2. Tlieil ; Senioii, ' Zoolof^. f orscluings- 

 l eiHeii,' J 1 1, 2. Theil, )). 848. 



+ MuBeiini of the Royal College of Surgeons of England, Cataloguo of Physiological 

 SericH, vol. 2, second edition, 1902. 



\ "Das Cent.ral-NcrvcnSy.stoni der Monoticnieii und Marsupialer," Seiuon, ' Zooiog. 

 Forschungsreisen,' HI, ji- 8 ; ' .Iciiain(lio Deukschriften,' VI. 



