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DE WALTER H. GASKELL. 



ticula of the gut, but also the retinal ganglion of the lateral eye 

 is in specially close connection with the end of the diverticulum 

 on each side. In fact, we find in the nearest living representa- 

 tive of the Trilobites a retina and retinal ganglion and optic 

 nerve closely resembling that of the vertebrate in close con- 

 nection with an epithelial tube, which has nothing to do with 

 the organ of sight, but is one of a pair of anterior gut diverticula. 



Al ' 



-rt.gl 



Fig. 10.— Section through one of the two anterior diverticula of the gut in 

 Artemia and the retinal ganglion. The section is through the extreme 

 anterior end of the diverticulum, thus cutting through many of the columnar 

 cells at right angles to their axis. AK, gut diverticulum ; rt. <jl., retinal 

 ganglion. 



It is impossible to obtain more decisive evidence that the 

 Trilobites possessed a pair of gut diverticula surrounded to a 

 greater or less extent by the retina and optic nerve of each 

 lateral eye. 



Such anterior diverticula are commonly found in the lower 



