SPONGES 43 



the closure of the oscula on injury to the sponge is 

 probably due to a mechanical rather than to a chemical 

 stimulation. 



Oscula close in running seawater containing small 

 amounts of ether (1/200), chloroform (1/200), strychnine 

 (1/15,000), cocaine (1/1000), and in deoxygenated sea- 

 water. They contract, but do not close, in dilute seawater 

 and at temperatures higher than normal, 35 to 45 degrees 

 centigrade. They remain open in currents of seawater 

 after which their closure is inhibited by cocaine 

 (1/10,000) and by atropine (1/1000), as well as by fresh 

 water. Their activities are apparently not controllable 

 by low temperatures, 25 to 9 degrees centigrade, by light, 

 nor by weak solutions of cocaine (1/50,000) and of atro- 

 pine (1/10,000). 



On the inner face of the oscular collar of Stylotella, 

 there is a conspicuous sphincter whose contractile cells 

 or myocytes are in many cases so close to the cavity of 

 the osculum as to be in direct contact with the water pass- 

 ing through it. It is probable that the epithelial lining of 

 this region of the osculum is made up of elongated encir- 

 cling and contractile epithelial cells such as Wilson has 

 shown to occur in the main efferent canals of this sponge. 

 This sphincter is doubtless responsible for the closure of 

 the osculum which may open in consequence of the con- 

 tractility or of the elasticity of the surrounding flesh. 

 The fact that the osculum closes in from about three to 

 eight minutes after the application of the stimulus and 

 that it opens in from about seven to fourteen minutes 

 when placed in running water shows that the sphincter is 

 a more rapid and efficient mechanism than that concerned 

 with the process of opening which after all may depend 

 upon simple elasticity. Thus the closing and opening of 



