176 NERVOUS SYSTEM OF VERTEBRATES. 



dominate in higher vertebrates. In the outer portion of the cell 

 layer are seen a few cells of relatively large size whose dendrites 

 are short and thick and more profusely branched than are those 

 of other cells, and enter only one or two glomeruli. Although 



Fig. 94. — An oblique section of the forebrain of Lampetra, passing through the 

 optic chiasma and liie olfactory commissure. a. 0., olfactory lobe; c. h., optic 

 chiasma; c. 0., olfactory commissure; /. b. ven., fore brain ventricle; /. 0. olfactory 

 bulb; ni, mitral cells; r. po., recessus postopticus; s, striatnam; //, optic tract. 



these cells are not highly specialized in cyclostomes they can be 

 recognized as the forerunners of the so-called mitral cells. 



In true fishes and amphibia the structure of the bulb is much 

 the same as in cyclostomes but there is a growing specialization 



