414 THE MICROSCOPE. 



Mr. Sorby, "it is the only blue solution in class C (of 

 which blocd is the type) that gives this particular spec- 

 trum." , The fluid emits a most pungent and disagreeable 

 odour when the bottle in which it is kept is uncorked. 



The common form of the Eughnce is represented in 

 Plate III. No. 67, a contracted, 6 elongated. Oxytriclia 

 are larger and the body more elongated ; their movements 

 are more impulsive, alternately creeping, running, and 

 climbing. In all the species digestive vacuoles are evi- 

 dent ; and they multiply by self-division, as well as ova. 

 Ehrenberg counted ten cilia anteriorly, and four or five 

 setae posteriorly. The species is found both in fresh and 

 brackish water. Plate III. ISTo. 70, represents a side view 

 of 0. gibba, ISo. 71, 0. Pellionella. In the genus Glau- 

 coma, Nos. 73 and 74, Ehrenberg saw "indications of an 

 alimentary canal." Dujardin places Glaucoma among 

 Paramoecia ; the body is oval and covered with cilia ; 

 mouth large, with vibratory valves ; increase takes place 

 by self-division. A re-examination of all the enumerated 

 species of Infusoria is quite necessary before we can come 

 to any safe conclusion as to their true affinities, especially 

 as many appear to be only larval forms of life. 



" The question of how far individuals belonging to the 

 same species may vary is one more intimately connected 

 with that department of Zoology which treats of the dis- 

 tribution of animals than their development. For it can 

 be readily shown that animals are capable of becoming 

 modified to an indefinite extent by the physical conditions 

 under which they are placed, and, indeed, that one species 

 may be, so to speak, made to pass into that of another ; so 

 that many of the apparently dissimilar animal forms found 

 on the earth may be more correctly viewed as varieties of 

 the same species, the differences between them being due 

 to the external agencies to which each has respectively 

 been subjected." 



The remarkable manner in which the Infusoria make 

 their appearance in fluids, and the seeming inexplicable 

 phases in their existence, led some early observers to start 

 a " spontaneous generation " theory of life ; but the re- 

 searches of M. Pasteur and others have completely exploded 

 this view of the formation of living organisms. The order 



