Il6 JOURNAI, OF CoMl'AU.\Tl\K Nf.UH()L<)(;> . 



cichla s'vaifisoui) , we meet in succession the following 

 parts (Plate XVI, Figs. 3, 13): 



1. The narrow pia mater. 



2. A wide layer of fibres, the external optic tracts. 



3. A narrow layer of densely packed Deiter's corpuscles. 



4. A wide granular layer, which contains no nerve cells 

 and only a few scattered Deiter's corpuscles. 



5. A wide layer of densely packed Deiter's corpuscles. 



6. A wide granular layer which contains no nerve cells 

 and only a few scattered Deiter's corpuscles. 



7. A very narrow layer of closely packed Deiter's cor- 

 puscles. 



8. A narrow granular layer which contains no nerve cells 

 and only a few scattered Deiter's corpuscles. 



9. A wide layer of densely packed Deiter's corpuscles. 



10. A narrow granular layer which contains no cells and 

 onlj a few scattered Deiter's corpuscles. 



11. A wide layer of densely packed Deiter's corpuscles. 



12. A narrow granular layer which contains no nerve 

 cells, but numerous scattered Deiter's corpuscles. 



13. An elongated nidulus, probably the spccijjc optic 

 nidulus. This nidulus consists of several longitudinal layers 

 of elongated, slender, pyramidal cells(') (Plate XVI, Fig. 6). 

 The major axes of these cells are arranged approximately 

 parallel to the axis of the nidulus. These cells are exceed- 

 ingly slender, being often six to eight times as long as broad. 

 In Swainson's thrush {Hylocichla szvainsoni) they are from 

 twenty-five to thirty micro-millimetres long and from three 

 to five micro millimetres wide. In aluminium-sulphate cochi- 

 neal and in haematoxylin preparations, these cells are densely 

 stained and possess dense nuclei. In addition to the cells just 

 just described, this nidulus is well supplied with Deiter's 

 corpuscles. 



I SriRiJA thinks the cells ol this nidulus are fusiform. " Studien iiber das centrale 

 Nervensystem der Vogel und Saugethiere." Von Dr. Ludwig Stieda, Leipzig, 1868, 

 p. 41- 



