107 



ON THE COLLECTION AND PRESERVATION OF FRESH- 

 WATER RHIZOPODS. 



By Dr. Eugene Penard (Geneva). 



{Read April VMlt, 1907.) 



Amongst the lower organisms which are found in fresh waters 

 there are few the study of which is so attractive as that of the 

 PJiizopoda. A special interest indeed attaches to these little 

 creatures owing to the fact that, as much from the systematic 

 point of view as on account of their finer structure, their develop- 

 ment, their physiology, even their ways and habits, there still 

 remains much to be discovered about them. 



Nevertheless, the systematic study of fresh-water rhizopods 

 is still too much neglected, probably because, by reason of their 

 minute size, special difficulties are dreaded. However, these 

 difficulties do not exist, or at any rate are not greater than 

 those met with in any other group ; in some respects even it 

 may be said that the study of rhizopods is comparatively easy, 

 and as regards the methods of obtaining specimens the difficulties 

 are not worth mentioning. 



After a fairly long experience in the manipulation of these 

 Protista I may hope perhaps to be able to offer some advice to 

 those who seek to understand them, and I may be allowed to 

 devote a few pages to the collection, examination, and preservation 

 of fresh-water rhizopods. 



Collecting. 



Collecting is as simple as possible, but here a distinction must 

 be made between ponds, streams, and marshes on the one hand 

 and those deep lakes, which require apparatus a little more 

 complicated, on the other. 



In the first case this is my procedure : Holding in my right 

 hand a test-tube 12 cm. (4| in.) long and 2 cm. (i in.) in 

 diameter, I close its mouth with my thumb and plunge my 

 whole arm in the water, so as to bring the test-tube to the 

 level of the mud, just to touch that sort of organic felt which 

 usually covers the bottom. Then, raising the thumb, I free 



Journ. Q. M. C, Series II.— No. 61. 9 



