THE ANIMAL WORLD OF WELL-WATERS. 253 



turbid, so that in this manner the mud will be caught in the bag 

 on drawing it up to the surface. 



In order to make the investigation a thorough one, a small por- 

 tion of this muddy matter, which generally consists of decaying 

 organic substances, is placed at once under the microscope, and 

 the organisms contained in it are determined. Besides doing this, 

 it is desirable to put a large quantity of the mud, say about one 

 hundred grammes, into a glass jar, which can be closed, and to 

 add some water from the well from which the mud was taken. 

 Then this should be quietly set aside for two or three weeks, in 

 some light spot, where the warm sunbeams can penetrate, so that 

 any eggs or germs present in the water may be destroyed. In 

 this way a great deal may yet be ascertained that could not have 

 been learned at the examination conducted immediately after 

 obtaining the sample. 



" But what does the mud from such a well contain ? " will be 

 asked by the reader with whom the question what it is that he 

 must guard against is of prime importance. This question is 

 here to be answered. First of all, let a glance be cast at the 

 woodcuts subjoined. Excepting Figs. 6, 7, and 8, the organisms 

 represented are visible only under the microscope, or at least 

 require, in order to be distinguishable, the aid of a powerful mag- 

 nifying lens. Nearly every particle of well-mud _ 

 contains the amoebae pictured in Fig. 1. They 

 resemble drops of flowing liquid, and constantly v j ff—^rP 9 

 change their form by sending out ray-like exten- n\ 

 sions. These extensions of the body are called > 

 pseudopodia, because their appearance creates the / 

 impression that the little animal is possessed of I 

 feet. But this is not the case ; the pseudopodia (ps) I 

 are formed only in the moment when a change in 1 k°af 1 

 location is desired, and they cease to exist when V&Jr~" "^ 

 the place is reached which the little animal FlG t 

 sought to attain. It can easily be proved that 

 these amoebae are animals, for they take up solid particles of 

 food, digest the same, and cast out again whatever has not been 

 assimilated. There is no vegetable organism which takes up solid 

 particles into its interior for sustenance. The propagation of the 

 amoeba takes place in the simplest manner imaginable, by fission : 

 a large specimen contracts at the center and ultimately divides 

 into two parts, so that the mother-animal is actually rent into 

 halves. In the body-substance of these beings, which are on the 

 lowest plane of organic life, the microscope discloses a number 

 of small particles, and a larger kernel (k), which is called the 

 nucleus. Besides this there are yet one or more clear spaces called 

 "vacuoles" (v). When fission takes place, the nucleus is also 



fl — v 



