20 GENERAL HISTORY OF 



existence of a nervous system in these animated atoms, 

 this might still be taken as a sufficient evidence of the 

 fact. 



Commencing, then, with the smallest, and apparently the 

 simplest, as to organization, of the Infusoria, in which the 

 eye is perceived, the first genera is that of the Microglena, 

 in which instance, as in the greater number of others, the 

 colour or pigment of it is red. When we reflect that in a 

 living creature, often less than the one-thousandth part of 

 an inch in diameter, so beautiful an organ as this exists, 

 the inference is almost certain that there must be systems 

 also for the performance of various other functions, but 

 which, by their very nature^ we are necessarily precluded 

 from discerning. 



By taking a glance at the tabular distribution of the 

 genera of each family in this work — a part which is of the 

 utmost value to the zoologist, and on which I have be- 

 stowed great pains — the reader will notice, at once, that 

 numbers of the genera of the Polygastrica are furnished 

 with one eye ; and, in some cases, which however are 

 more rare, with two. 



In the Rotatoria, the number and position of these 

 organs may be regarded as excellent characteristics of the 

 genera. In the greater proportion of these, as before 

 stated, the animalcules have two, and, in some instances, 

 three eyes ; whilst, in one genus, the Theorus, as many as 

 seven or eight have been distinctly recognized on each 

 side of the head. When the eyes are situated in front of 

 the oesophagal bulb, to which the teeth are attached, they 

 are termed frontal eyes; and when behind this bulb, 

 cervical eyes. They are sometimes disposed in a line. 



