704 



SCIENTIFIC RECREATIONS. 



of its structure to that of the plant, but differs from it in the entire absence of 

 the ' cellulose wall ' or of anything that represents it, the cell-contents being 

 enclosed in only a single limitary membrane, the chemical composition of 

 which, being albuminous, indicates its correspondence with the primordial 

 utricle. In its young state it seems always to contain a semi-fluid plasma, 

 which is essentially the same as the protoplasm of the plant, save that it 

 does not include chlorophyl granules, and this may either continue to 

 occupy its cavity (which is the case in cells whose entire energy is directed 

 to growth and multiplication), or may give place, either wholly or in part, 

 to the special product which it may be the function of the cell to prepare. 

 Like the vegetable cell, that of animals very commonly multiplies by 



Fig. 828. Animalculse found in stagnant water. 



A, Cyclops Quadracornis. 



B, Anguillula. Fluviatillis. 

 c, Actinophrys. Sol. 



r>, Coleps Hirtus. 

 E, Vorticella. 



F, Amboeba princeps. 



G, Acineta mystacina. 

 H, Oxytrycha. 



I, Triophthalamus dorsalis. 

 j, Polyarthra. 



duplicative subdivision, it also (especially among protozoa) may give origin 

 to new cells by the breaking up of its contents into several particles." 



The protozoa are microscopic creatures consisting of one or more 

 cells, and are infinitely little, thousands existing in a drop of water. They 

 have no distinction of sexes, and their generation takes place by subdivision 

 or blending of cells. The infusoria are the highest of the protozoa, and 

 were formerly included amongst the radiata. Their numbers are infinite, 

 and in a drop of water (see fig. 828) some very interesting specimens will be 

 found. These infusoria are merely sarcode, or a jelly-like substance, and 

 some have cilia, or hairy appendages, with which they agitate the water and 

 cause a kind of current which brings them food. It is this partaking of 

 food which has served to divide the lowest animal from the lowest vegetable 



