POND LIFE 



767 



partially opened shells, giving a view 

 of its fringed syphons. It is a very pvu- 

 litio creature, the outer gills of a ieniale 

 ha\ing been computed to contain some 



THE BEAUTIFUL AND INTERESTING VOLIOX 

 GLO BATON. 



300,000 young shells. Like most of the 

 pond mollusca, the Swan-mussel can boast 

 of ancient lineage, for eight fossil species 

 are to be found in the Eocene formation. 

 Indeed, quite apart from their beautifully 

 formed shells, and varied habits, the 

 pond snails and mussels are an interesting 

 group of animals on account of their 

 forming such a remarkable and striking 

 link with the past geological fauna of our 

 country. 



No description of pond life would hv 

 complete without a brief reference to 

 some of the interesting and remarkable 

 forms of plant life to be found in that 

 environment. Of the Bladderwort I liave 

 already given a description in dealing 

 with the life and habits of the Water 

 Fleas (p. 721). First in interest, on 

 account of its remarkable power of loco- 

 motion, is the J'olvox Globalor, which be- 

 longs to that debatable group of more or 

 less simple organisms that partake of the 

 characteristics of both plant and animal 

 life. When seen under a moderate magni- 

 fication the Volvox presents the appear- 

 ance of a tiny hollow sphere, the outer 

 walls of which look as if formed of a 

 green lattice-work of cells. Careful and 

 critical inspection will also reveal the 



fact that each cell bears externally a 

 pair of exceedingly delicate hairs or cilia, 

 by means of which the Volvox mows 

 through the water, and that certain 

 cells are of a complex character, in which 

 the young are formed. The Volvox, by 

 means of its cilia, moves through the 

 water with a rolling motion, and at a 

 fairly rapid rate, and is a most beautiful 

 and interesting object to watch by the 

 aid of a low-power object glass under the 

 microscope, when not only its move- 

 ments can be closely followed, but the 

 growth of the young, and their rolling 

 movements within the parent sphere until 

 its rupture sets them free, may be 

 witnessed. 



Next in interest to the Volvox are the 

 Diatoms, those wonderful unicellular 

 plants which secrete an indestructible 

 skeleton of silica, the exquisitely delicate 

 markings of which are the delight of all 

 microscopists. Most of the pond Diatoms 

 have the power of movement, travelling 

 through the water at varying speeds. 

 Exactly how the Diatoms propel them- 

 selves through the water is still a debatable 

 subject. They abound in eveiy pond, 



A//C A'.l S TEKIA S KO TA TA . 

 One of the most beautiful Dcsmids to he found in ponds 



frequently forming an oli\'e green coaling 

 to the stems of the water-wecils. and 

 sometimes quite a thick scum o\er tin,' 

 surface of the pontl. 



The Desmids are near relations of the 

 Diatoms, but though they are capal)Ie 



