lOfi Transactions of the Society. 



where; the sediment and water-plants of every little stream or 

 pond will yield them more or less plentifully, Sphagnum moss 

 always provides multitudes of them with a habitat, and the mosses 

 growing on walls, trees, and even on the pavements of towns 

 provide shelter for their appropriate secies. 



These unicellular animals have i.xovided valuable subjects of 

 study to biologists, and their life-histories and habits, of which 

 little is now known, are sure to provide a mine of information to 

 naturalists in the future ; how such creatures, without any differ- 

 entiated organs, can build their habitations with such svmmetrv 

 and marvellous accuracy of workmanship is a question which 

 cannot fail to strike the most cursory observer. 



The sub-class Ehizopoda comprises the orders Amoebina, or 

 naked forms, and Conchulina, or those furnished with a test ; the 

 families Arcellida and Euglyphina include the genera whose tests 

 yield the most interesting results from a microscopical examination. 

 The size of the tests usually lies between lo/x and 150/^in length, 

 although specimens up to 500/a do occur. For locating a specimen 

 in a drop of " material " a ^-in. objective, with a large field, is 

 most convenient ; for the detailed examination a £-in. objective 

 is best as a rule, but may often be usefully supplemented by a 

 |-in. ; for the detailed examination of such tests as those of the 

 Cyphoderise and of individual scales, etc., a ^-in. oil-immersion 

 lens is required. 



For the modus operandi of collecting and mounting the tests 

 Penard's paper, " On the Collection and Preservation of Fresh- water 

 Ehizopoda,"* should be consulted. If drawings are made, a cam era - 

 lucida should be used to ensure accuracy, and the dimensions 

 should be checked by measurements of the object itself; micro- 

 photography unfortunately does not as a rule give good results 

 unless the tests are flat or parts of them specially prepared. 



For the identification of species Cash and Hopkinson (.2) f or 

 Penard (4) should be consulted ; the latter work embodies nearly 

 all the information available on the subject. 



The Ehizopoda are propagated by three methods : 



1. By means of spores which grow into amoeboid individuals 



and then construct tests. 



2. By " budding." 



3. By simple division into two individuals. 



Very little is known of the process by which the tests are made in 

 the first two cases, but the naked animal must of necessity either 

 secrete its test or search for the materials with which to construct 

 it. In the third case the process can frequently be seen in some of 

 its stages, but probably has never been observed in its entirety, 



* Journ. Quekett Micr. Club, 1907. 



t The figures in brackets refer to the Bibliography at the end of the paper. . 



