24 THE MICROSCOPE. Feb. 



pores can hardly be noticed except by using colored par- 

 ticles which have been observed to enter the sponge. In 

 one case indigo being used gave the whole sponge a bluish 

 tint. But the outflow has been likened by observers to a 

 continual fountain. A little sponge placed in a saucer of 

 water sent out a stream twelve feet long. This was in 

 open air, offering comparatively no resistance. It must 

 be apparent that an enormous force must be required to 

 send out a stream against the necessary resistance and 

 pressure of- the surrounding water. Again, is this inflow 

 and outflow continuous, especially the inflow, which may 

 be caused by external pressure alone ? Observations 

 have shown the negative. It was found that the opening 

 of both the pores and osculae are within the control of 

 the sponge and can be opened and closed at its pleasure. 

 Here the wonder increases : how, without any a]>parent 

 force — controlling organ — power is exerted. The seat of 

 power in sponges is supposed to be in the amoeboid bod- 

 ies, mentioned hereafter. But even were this conflrmed, 

 it would be ojjen to further investigation how these bod- 

 ies can exercise force upon another part of the sponge 

 separated from, and without any noticeable connection 

 with them. 



Canals. — If there are two currents of water, there 

 must necessarily be two different water ways, each serv- 

 ing its own purpose. The incoming currents are of 

 course small, their contents after being utilized enter a 

 larger opening acting as a cloaca, and thereby leaving 

 the body. The simplest form {Ascetta primordialis) has 

 but one osculum, being the mouth of a large central cav- 

 ity, into which the smaller influent canals enter. In the 

 higher orders the canal system is very diverse, intricate 

 and numerous. The water entering the pores does not 

 in all cases pass through simple ducts before reaching 

 what may be called digesting chambers, but in the sim- 

 pler forms enters at once into what Kent calls ampul- 



