68 



Journal of Entomology and Zoology 



runs to the ectoderm of the oral disc and to the muscles of the 

 oesophagus. 



Ackerman, 1902, gives figures of the nervous system in Cucii- 

 maria. Retzius, 1906, by means of the silver method gives a 

 mosaic picture of the epidermal cells. Between these cells are 

 small oval fields, the sense cells between the polygonal areas or 

 supportive cells. These are partly between two cells, partly be- 

 tween several supporting cells; they are not regularly arranged. 

 Reimers, 1912, discusses the development of Synapta and gives 

 something of the nervous system. Haanen, 1914, in Mesothuria, 

 is not inclined to accept Herouard's (1890) suggestion that the 

 inner nerve band is chiefly a motor nerve. Very fine intestinal 

 nerves from the circum-oral nerve ring are found in this form as 

 well as the thicker nerves found by other observers. Every ten- 

 tacle and every foot has its own nerve, the first from the circum- 

 oral nerve ring, the second from the radial nerves. The foot 

 nerves are .029 inches broad and smaller and more circular in out- 

 line than the tentacle nerves. There seem to be at least some 





Nervous system of Holothuroidea. A. Diagram of a sea-cu- 

 cumber showing superficial and deep central systems, branches to 

 tentacles and tube-feet and the inner and outer nerve plexus. B. 

 Section through body-wall of Holothuria showing central band 

 in dark with nerve to a tube-foot. C. Nerve supply to tube-foot. 

 Hamann. D. Sense papilla of Synapta supplied by a nerve. Ha- 

 mann. E. Oral end of Synapta showing location of sense pores. 



