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Amphioxus, which, as all beginners in zoology learn, 

 supplies us with an ideally simplified chordate, 

 goes too far for our present purpose in the simplifi- 

 cation of its eyes, which have either vanished 

 entirely by degeneration or never developed. 



"^ B Ic. 



Fig. 96. Light Cells of Amphioxus: (A) Forepart of a Young 

 Artifhioxus, Enlarged; (B) Cross-section of the Spinal Cord of 

 Amphioxus (from Plate, A, after Joseph, B, after Hesse.) 

 (From Allgem. ZooL, Gustav Fischer.) 

 For details, see p. xxxvi. 



According to Plate (1924, p. 494) the lancelet 

 (Amphioxus) when resting on the sandy bottom 

 is supposed to sense the direction of the light by 

 means of long rows of minute eye-like organs, 

 which are deeply buried in the spinal cord and 

 extend along each side of the back above the 

 notochord. Each little eye consists of a single 

 cell, supposed to be sensitive to light, backed by 

 another cell which is concave and deeply pig- 

 mented. A much larger spot of pigment at the 



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