FEESH-WATEE SPONGE 69 



person, for, if a piece of sponge be gently pressed be- 

 tween the thumb and finger, it crumbles to fine par- 

 ticles which feel gritty. Further, a close examina- 

 tion, with or without a hand - lens, will show numer- 

 ous fine openings scattered over the surface if the 

 specimen really be a sponge. In collecting Spongilla 

 put the specimen together with the object to which 

 it is attached into a pail with an abundance of water, 

 and handle as little and as gently as possible. By 

 changing the water three or four times a day speci- 

 mens may be kept alive for several days. A good plan 

 is to set the pail where a slow stream of water may 

 flow through it. The following are especially good 

 places to find specimens : the rocks at the foot of a 

 mill-dam, the sluice-ways and gates of a mill, and the 

 under side of rocks and logs in swift-flowing streams. 

 There is almost always a possibility of finding them in 

 clear, rapid streams, but never in water which is per- 

 manently muddy. The best specimens are to be found 

 between July and December. 



To prepare alcoholic specimens for preservation drop 

 pieces of the branches of the living Spongilla into about 

 fifteen or more times their bulk of absolute alcohol and 

 change the alcohol at the end of two or three hours. 

 The color of the specimen is altered, but the structure 

 is well retained. 



In the examination will be used the hand-lens, com- 

 pound microscope, acetic acid carmine, hydrochloric 

 acid, fine bristles, chalk or indigo, and forceps. 



Method of Excmiination. — Living Spongilla should be 

 examined where found if practicable. If removed to 

 the laboratory the examination should be made at the 

 earliest possible moment, as it is very difiicult to keep 



