Microscopical Essays. 



4*3 



frequently to be found in our ditches, was given to a polype. 

 The fubftance of this (kin was foon reduced into a pulp, confihV 

 ing of little black fragments ; on examining the polype with the 

 microfcope, thefe particles were perceived to be driven about the 

 ftomach, and to pafs from head to tail, and into their arms, even 

 where thefe were as fine as a thread • they were afterwards forced 

 into the ftomach, and from thence to the tail, from whence they 

 were again driven into the arms, and fo on. 



The grains take their tinge from the food which nourifhes the 

 polypes ; thefe grains become red or black, if the polype be fed 

 with juices that are either red or black 5 and they are more or lefs 

 tinged with thefe different colours, in proportion to the ftrength 

 and quantity of the nutritive juices. It is alfo obfervable, that 

 they lofe their colour if fed with aliments that are not of the fame 

 colour with themfelves. 



The polypes feed on the greater part of thofe infecls that are to 

 be found in frefh water. They may be nourilhed with worms, the 

 larva of gnats, &c. they will alfo eat larger animals if they are 

 cut into fmall pieces, as fnails, large aquatic infecls, fraall fifh, 

 butchers meat, &c. Sometimes two polypes feize the fame 

 worm, and each begins to fwallow it's own end, continuing fo to 

 do till their mouths meet, Fig. 8, Plate XXiV. A ; in this pofition 

 they remain for fome time, at laft the worm breaks, and each has 

 it's (hare ; fometimes the combat does not end here, for each 

 continuing to difpute the prize, one of the polypes opens it's 

 mouth advantageoufly, and fwallows the other with it's portion of 

 the worm, fee Fig. 14, Plate XXIV. A ; this combat ends more 

 fortunately for the devoured polype than might be at firft ex- 

 peeled, 



