Fig. 21 Detail of the optic part of the tectum (left side) near its rostral end. 

 The optic tract is not impregnated, but the area of termination of this tract, 

 as revealed by other preparations, is marked col. sup. Two neurons of the optic 

 tectmn are shown, the lower one being drawn in from the next adjacent section 

 in front. Some dendrites of each of these neurons arborize in the neuropil 

 reached by the optic terminals, while others pass farther ventrally into the col- 

 liculus inferior (col.inf.). Terminals from both the acoustico-lateral lemniscus 

 (Im.) and the spinal lemniscus (tr.sp.t.) are seen to reach the neuropil of the optic 

 part of the tectum, though their chief area of distribution is farther ventral and 

 caudal. X 74 (cvic, 176). 



Fig. 22 A single neuron from the right side of the tectum one section caudad 

 of figure 24. Some of the dendrites were cut off and are drawn in from the. ad- 

 jacent sections by superposing camera outlines made on tracing paper. The 

 position of the acoustico-lateral lemniscus is indicated at Im, though the tract 

 itself is not drawn. X 74 (cvic, 182). 



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