26 GENERAL HISTORY OF 



certain to meet with animalcules. If there be any drains, 

 however, communicating with them, the chances are that 

 they contain only the common species, which will, by a 

 little practice, be readily distinguished by their motion, 

 general appearance, and colour. The indications of the 

 presence of Infusoria are specks moving about in the water, 

 or an apparent mouldiness around the stalks of the 

 Lemnee, &c. Should these appearances not be discerned 

 under the middle power of your magnifier, throw away the 

 water, and repair to some more favoured pool. Be 'careful 

 to take only a small portion of the vegetable matter in 

 your vessel, as its decay, and consequent evolution of gas, 

 may soon kill all your animalcules. This must be con- 

 stantly borne in mind. Clear pools of water, in the spring 

 of the year, are the favourite places of resort for the Volvox 

 globator; clear water, slowly running in clay or chalky 

 soils, for the Bacillaria and Arcellina. House gutters, and 

 tubes placed to receive the rain water, often contain a rich 

 supply. In the winter, you may search for them in water 

 among dead leaves, reeds, &c., which may be taken out, 

 and their contents shaken off into some clear water ; while 

 the species which attach themselves firmly to these objects 

 may be examined without their being removed from them. 

 Dr. Ehrenberg states that he has met with good success 

 in the winter under bridges, around the piers and outworks, 

 and even in frozen ditches beneath the ice. When you 

 have filled your vessels, cork them carefully, so as to 

 exclude the air, for the shaking of the carriage, when 

 a quantity of air is left in the vessels, will often destroy 

 them before you arrive at your place of destination. In 

 this respect, my mode of proceeding differs from that of 



