154 GEORGE T. MCNAIR. 



the responses of the oscula, ostia, and choanocytes first to 

 mechanical and then to chemical stimuli. He studied the 

 reactions of the sponge to flowing water, injuries, and cuts. 

 Likewise he studied the effects which ether, chloroform, cocaine, 

 strychnine, and atropine produced upon the sponge and compared 

 his results with the known effects of these drugs on smooth 

 muscle and on ciliated tissue. 



Ephydatia fluviatilis (L.), the fresh-water sponge with which 

 the experiments described in this paper were made, differs so 

 greatly in structure from Stylotella that it was impossible to 

 duplicate many of Parker's experiments. The responses of the 

 oscula were watched to determine the effects of various mechan- 

 ical stimuli such as injuries, electrical stimulation, and changes 

 in temperature. The purpose was to determine the effects of 

 such stimuli and the rate of possible transmission of these effects 

 from one part of the body to another. 



All the sponges used in the following experiments were collected 

 in small ponds along the railroad tracks in the neighborhood of 

 Hammond and Bumngton, Indiana. They were carried to the 

 laboratory in fruit jars and then transferred to large jars of 

 slowly running water. 



The ponds from which the material was collected l were 

 shallow, often almost filled with bulrushes. The bottoms were 

 covered with mud and cinders. The sponges were, for the most 

 part, growing on the under side of old railroad ties floating in 

 the water and were more or less cushion-like in form and without 

 much branching. Some, however, were found growing on the 

 submerged parts of plants or on leaves, but here their form 

 was more spreading, following that of the body to which they 

 were attached. 



The body of the sponge is dotted all over with very small 

 dermal pores or ostia. The oscula are relatively prominent little 

 chimneys of dermal membrane, standing our from almost any 

 point on the suface. Bundles of smooth, pointed, and almost 

 straight silicious spicules make up the skeleton. The internal 

 canals of the body meander irregularily between these bundles 

 of spicules. The dermal membrane, which completely envelops 



1 See Shelford, "Animal Communities in Temperate America," Chapter VIII. 



