HKA1N OF TELEOSTS 



Fie. 128. Transverse sections of forcbrain in various vertebrates to show the condition 



of inversion (thick roof) in A, n, and c and eversion (thin roof) in D, E, and F. 



A, lamprey; B, frog; C, chelonian; D, chimaera; E. sturgeon; F, teleostean; pall, pallium; 



sep. septum; str. striatum. (From Kappers, Huber, and Crosby.) 



m. 



Fig. 129. Sagittal section of brain of the gurnard, showing the swellings in the 



spinal cord at the point of entry of the nerves from the fin. 



C. cerebral hemisphere; ce. cerebellum; hy. hypothalamus; in. midbrain; no. swellings of 



spinal cord; v. valvula. (From Scharrer, Z. verg. Physiol. 22.) 



other vertebrates, in producing precise and correctly timed movements. 

 It is enormous in the Mormyridae, where it may assist in direction- 

 finding by electrical pulses (p. 253), perhaps acting as a timing device. 

 The medulla oblongata is also well developed, having special lobes 

 connected with the entry of the lateral line nerves and gustatory fibres 

 of the cranial nerves. In the gurnard, Trigla, there are chemical 

 receptors in the elongated fins. These are innervated from spinal 

 nerves, and there are swellings of the dorsal part of the spinal cord at 

 the points where these nerves enter (Fig. 129). 



