A WORLD IN THE WATER 89 



spermatozoids. With the maturing of these 

 egg cells the colony breaks up. 



The minuteness of many species of algae 

 inhabiting fresh water causes them to be diffi- 

 cult subjects for study. Most of the forms 

 which present remarkable features can only 

 be really appreciated when viewed under the 

 microscope. A very good way of observing the 

 general character of some of our fresh-water 

 algae is by floating them out in a dish of water, 

 placing a sheet of white paper beneath them, 

 and gradually draining the water away. Such 

 kinds as Batrachospermum and Lemanea may be 

 treated in this way. The former is rather un- 

 pleasantly shmy to the touch, but when floated 

 out is seen to be composed of branches which 

 are really very beautiful, in that they resemble 

 a string of beads. The commonest kind is of 

 a brownish colour, as a rule, though it varies 

 in different localities. The Lemaneas are very 

 abundant in streams with a rocky or stony bed, 

 and these are worth floating out on paper, in 

 order that their ohve-coloured branches, some- 

 times a foot in length, may be examined. The 

 Zygnemas are excessively common in ditches 

 and ponds, where they resemble cloudy masses 



