216 SYSTEMATIC ZOOLOGY FOR TEACHERS. 



escape of the air at the gr?pe-vine plugs immersed in the tank of water (or 

 tanks as the case may be ) . During all this process of the filling of the 

 jar and the tubes, the bubbles escape in a constant stream from the. end of 

 this plug (or these plugs, when the tanks are connected up in series). 

 When the water in tube C reaches the bend at top, it begins to siphon 

 out, and if the influx has been gauged properly, runs out faster than the water 

 is delivered. A syringe valve at K prevents the water from sucking back into 

 tube D. Air is sucked in through tube B to replace the water in the jar. 

 During this time the bubbling of the air out of the grape-vine plugs inter- 

 mits. After the jar empties, the process begins over again. My apparatus 

 works automatically for months with scarcely any attention. 



Morgan and Wright bicycle valves placed in the individual tubes that 

 supply each jar contributes to the successful operation of the mechanism. 

 Where a number of aquaria tanks are connected up in series, it is necessary 

 to adjust these valves so that air will be forced out through each of them. 



I use my jars or tanks, thus aerated, for keeping alive hydras, copepod 

 crustaceans, and oth?r forms of minute fresh-water organisms, that readily 

 wash out of an aquarium through which a stream of Avater flows. 



SYSTEMATIC ZOOLOGY FOR TEACHERS. 



BY 



C. J. Maynard. 

 Forms and Species of Sponces. 

 ( continued ) 



Among species of sponges, the simplest forms which we find are single 

 cylinders. A species which often grows as a single cylinder is the tube 

 sponge, ( see plate VIII, May No. ) but these sponges frequently produce 

 buds from the base, (see fig. 78, page 172, also fig. 99, page 217) a proc- 

 ess to be described under reproduction. These buds grow upward, and thus, 

 in some cases, form colonies. See fig. 82, page 180 and fig. 84, page 182, 

 where two cylinders are seen growing side by side. Sometimes other buds 

 form, and under favorable circumstances, a number of cylinders may be seen 

 growing side by side. I have found as many as twenty cylinders in one 

 case in a single colony. The^ cylinders usually remain separate, often grow- 

 ing upward, as in the specimen figured on page 182, but sometimes they 

 adhere together for the basal portion, as seen in the specimen given on page 

 180. More rarely, however, the cylinders are found fastened together for the 

 entire length. Such a specimen is given in fig. 100. 



