34 journal of Comparative Neurology and Psychology. 



8. THE CEREBELLAR, OCCIPITAL AND BODY GROUPS. 



TABLE IX. 



Table showing the time of appearance and number of buds in the cerebellar, occipital and body groups. 



This group of buds includes (A) those lying on the cerebellum 

 and innervated by the meningeal twig of the ramus, lat. acces. 

 (B), those lying over the occipital region and innervated by the twigs 

 of the ramus lat. acces. given off before that nerve leaves the 

 skull; and (C) buds on the body innervated by the ramus lat. 

 acces. There is no overlapping of this group (C) with the pre- 

 ceding group, the body buds being entirely separate from buds 

 of the posterior operculum until in the 20| mm. embryo, when 

 they become continuous. 



It will be noticed from the table that the cerebellar and occi- 

 pital groups appear simultaneously in the 20J mm. embryo. 

 It is not possible to separate these two groups at this stage, the 

 cerebellar being continuous with the occipital. Doubtless, if a 

 series had been cut between the 17^ mm. embryo, where they 

 are not present, and between the i.o\ mm. embryo, they would 

 be found to be distinct groups. The separation has been made 

 in cataloguing, by including all buds in front of the posterior 

 portions of the cerebellum in the cerebellar group, and all those 

 back of that point in the occipital group. 



The failure of the cerebellar and occipital groups to appear 

 simultaneously with the opercular or post-orbital group, with 

 which they are related in position, is difficult to explain. They 

 have the same innervation practically in Ameiurus that the body 

 buds have and it was thought at first that possibly they followed 

 the same rule that is so often illustrated in the groups anterior 

 to this, of the appearance of buds on the peripheral distribution 

 of the nerves sooner than on the proximal. However, buds on 

 the body appear first on the anterior segments and spread from 

 there posteriorly, and the same occurs, as we shall see later, in 

 the case of the oesophageal buds. 



