ox 'I'PTE DEVELOPMENT OF ARANEINA. 88 



(16) The development of the posterior median eyes is connected 

 with that of the hrain. Their development is quite different from 

 that of the other eyes ; but all the eyes are dermal in origin, not 

 neural. And the nerves of the eyes enter always from the inner 

 ends of the ectoderm cells. 



(17) A pnii- of coxal glands opens at the base of the third 

 appendage. The glandulai- portion of it is formed from a portion of 

 the cœlom, while its duct is formed frc^m an ectodermic invagination. 



(18) The alimentary canal of the spider is formed from the 

 ectoderm and the endoderm. The pharynx, the œsophagns, the 

 stomach, and the anus ai-e produced from the former, and the intes- 

 tine from the la t fer. 



(19) Tlie Malpighian tubes are produced neither from the ecto- 

 derm nor from the stercoral pocket. They are mesodermic in origin. 



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