NERVOUS SYSTEM. VERTEBRATA. 101 



the crossing of the optic nerves the left below the right 

 as well as the union of the lobi inferiores in the mid-line 

 behind the saccus vasculosus. The olfactory bulbs and 

 peduncles have been removed. 0. C. 1380 A 15. 



D. 110. The head of a Barbel (Barbus vulgaris) with the brain 

 exposed from above. The cerebellum is considerably larger 

 than in the Tench; it is oblong and overhangs the anterior 

 part of the medulla. The optic lobes are well-developed. 

 In the mid-line the outer layers of the tectum are deficient, 

 exposing a transparent commissural area of triangular 

 outline through which the valvula cerebelli is indistinctly 

 visible as in the Carp. The left basal ganglion has been 

 removed, exposing the short thalamencephalon with the 

 ganglia habenulae two small whitish excrescences on the 

 dorsal margins of the thalamus. The crossing of the optic 

 nerves the left above the right can also be seen. From 

 the anterior end of the corpora striata delicate olfactory 

 peduncles are given off. The olfactory bulbs in this and 

 other Carps lie close to the olfactory capsules : they are not 

 shown. 0. C. 1308 E. 



D. 111. Brain of a Bleak (Alburnus alburnus). It closely re- 

 sembles that of the Tench (D. 108), except in the somewhat 

 smaller relative size of the " lobus impar." 



D. 112. The brain of a Koach (Leuciscus rutilus) exposed from 

 above. The "lobus impar " and lobi vagi, though dis- 

 tinctly visible, are far less developed than in the other 

 specimens of Cyprinoid brains. 



Presented by Mr. S. Epprett. 



D. 113. The head of a Pike (Esox Indus) with the brain exposed 

 from above. For that of a Teleostean, the brain is long and 

 narrow, with tapering medulla and open rhomboid fossa. 

 The cerebellum and optic lobes are considerably developed, 

 the latter having a long oval shape. The epiphysis is 

 saccular and pear-shaped ; it overhangs the small basal 

 ganglia and extends forward to the anterior extremity of 

 the olfactory bulbs, which are sessile on the cerebrum. 



