10 



G. H. Parker 



TABLE I 



Times in hours and minutes during which in the course of three days oscula 1,2, and J were open or closed 



Since the three oscula whose conditions are recorded in Table i 

 were on the same colony and near together and were exposed to 

 almost identical surroundings, the fact that osculum i was closed 

 on the average one hour in every two and a half, while oscula 2 

 and 3 were closed only one hour in every eighteen, must be attrib- 

 uted to the difference in constitution of osculum i as contrasted 

 with that of the other two. The condition of general openness as 

 exemplified by oscula 2 and 3 is doubtless typical for these organs. 

 At least in any vigorous sponge under normal conditions, the 

 majority of the oscula will be found open much of the time. When 

 an osculum opens or closes, it does so in response to some stimulus. 

 To ascertain what the effective stimuli are in this form of response, 

 1 have studied the oscular reaction in relation to mechanical and 

 chemical stimulation and to heat and light. 



a. Mechanical Stimulation 



When at low tide a specimen of Stylotella was transferred from 

 the shallow water of the outside to the laboratory tank, an opera- 

 tion that required about ten minutes, it was found that the anima 

 that in the outside water had most of its oscula open usually had 

 the majority of them closed when it had arrived in the laboratory, 

 notwithstanding the fact that it had not once been exposed to the 

 air during this transfer. At first it was suspected that this closure 

 of the oscula was due to the disturbance caused in loosening the 

 sponge from the bottom, etc., but it was found that this was not 



