Reactions of Sponges 39 



5 The ostia close on injury to neighboring parts, in solutions 

 of ether (0.5 per cent), chloroform (0.5 per cent), strychnine 

 (t5¥o¥)> and cocaine (toVt)- They open in solutions of cocaine 

 (to^oo)- and of atropine (yoVo)? in dilute seawater, deoxygenated 

 seawater, and warm seawater (35° C). They are apparently 

 unaffected by mechanical stimulation, except injury, by low tem- 

 perature, and by light. 



6 The choanocyte currents cease in solutions of ether (0.5 

 per cent), and of chloroform (0.5 per cent), in diluted seawater 

 and at high temperatures (40°— 45° C). They become slow at 

 low temperatures (9° - 10° C), and fast in solutions of strychnine 

 (y^ioo)- In deoxygenated water they first become fast and then 

 cease. 



7 The flesh of Stylotella is capable of contraction, but such 

 contractions give the sponge only a shrivelled appearance with- 

 out changing its general form. 



8 The currents in Stylotella are constant in direction and give 

 no evidence of reversal. They are controlled by the ostial and 

 oscular sphincters. They produce a pressure equivalent to 3.5 

 to 4 millimeters of water. The pressure necessary to break 

 through the closed ostia is 10 to 15 millimeters of water and through 

 the closed oscula somewhat more. 



9 The reactive organs of Stylotella, the ostia, the oscula, the 

 flesh, and the choanocytes, are all more or less independent of 

 one another and their action is changed by direct stimulation. 

 In the ostia, oscula, and flesh contraction is accomplished by 

 spindle-shaped cells, the myocytes, which resemble primitive, 

 smooth muscle-fibers. 



10 The body of Stylotella is almost without transmission and 

 such transmission as is present is so sluggish in character and so 

 silght in range as to resemble transmission in muscles and not in 

 nerves. It is probable that Stylotella possesses no organs that 

 can reasonably be called nervous. 



11 The nervous and muscular systems of metazoans were not 

 differentiated simultaneously (Kleinenberg, O. and R. Hertwig) 

 nor independently (Claus, Chun), but muscles, independent effec- 

 tors, as represented by the sphincters of sponges, were the first 

 of the neuromuscular organs to appear and these formed centers 



