1 82 RAMBLES AND REVERIES. 



allies the Diatoms, which thrive in both fresh and 

 salt water. My experience leads me to the con- 

 clusion that they are most easily found in shallow 

 ponds on open moors and on damp bog-moss. If a 

 bit of this bog-moss (Sphagnum) feels slimy to the 

 touch, the probability is that we have come upon a 

 crop of desmids. When found it is as well to wash 

 them into a glass bottle filled with clean water, 

 where they will soon settle on the sides and bottom, 

 from which they should be detached by a camel's- 

 hair brash, and deposited on a slip of glass for 

 inspection. Most desmids are free cells, but in 

 some cases several individuals are grouped together 

 in the form of a star or disc ; others, again, take the 

 form oflong threads or ribbons, and are consequently 

 called filamentous desmids. 



Desmids possess a transparent membranous 

 envelope or case, entirely destitute of silica, the 

 flinty material which accompanies diatoms. This 

 case contains the chlorophyll, or green colouring 

 matter, which renders these tiny plants so con- 

 spicuous. They, no doubt, constitute the chief 

 food of fresh-water animalculae, and almost every 

 observer of them has seen the rotifer greedily suck 

 out the contents of the envelope and cast away the 

 empty, but still beautiful, case. While living they 

 have the power of gliding through the water with 

 an even graceful motion, while their hyaline cover- 

 ing, sparkling with emerald points, and filled with 

 diamond-like granules, helps to make up a vision 

 of beauty surpassing that which AlaJdin's lamp 

 revealed. 



