Stroud, Mammalian Cerebellum. 89 



human embryo, the cerebellum is seen as early as the second 

 month as a thin plate arching over the cephalic part of the met- 

 epicoele (fourth ventricle). From this plate, which enlarges 

 only gradually, is formed the middle lobe; later the lateral lobes 

 grow out at the sides." 



" The cerebellum consists of two lateral hemispheres joined 

 together by a median portion called, from its peculiar appear- 

 ance caused by the transverse furrows or ridges upon it, 

 the worm or vermiform process, .... in mammals it is 

 the first part to be developed and to be marked off into subdi- 

 visions." (Idem., Vol. Ill, Part I, p, 69.) I shall show that 

 the vermis is not the first part to be developed and marked off 

 into subdivisions. 



1894. Schaper (28, 489) published an account of his ex- 

 haustive investigations upon the development of the cerebellum 

 in Teleosts. He confirmed Herrick's discoveries and made fur- 

 ther observations of great value. His work, and also that of 

 Professor Herrick, will remain as landmarks in the history of the 

 comparative development of the cerebellum. 



Having thus given a brief resume of the opinions of the 

 men who have made a special study of the development of the 

 cerebellum during a period of nearly a century, I proceed to 

 a consideration of the facts which lead me to differ from some 

 of the views hitherto advanced. 



The Epencepfial. 



Is the epencephal a distinct brain segment ? This is a 

 question which perhaps can not be settled at once.^ But the 

 writer believes that, as has been stated by Wilder (36, 523), for 

 the purposes of comparative and descriptive neurology it would 

 be a great convenience to regard the epencephal as a distinct 

 brain segment ; hence some evidence will be given in support 

 of that view. 



In order to reach a logical conclusion we must first decide 

 what constitutes a brain segment. In the case of the primary 



'In this connection, see also Osborn (25, 490). 



