INFUSORIA. 389 



CHAPTER XXI. 



INFUSORIA. 



WE will now resume our examination of the drop of pond- 

 water, and the fragments of Myriophyllum, which have 

 been waiting far us in the live-box. 



Our attention then shall first be given to some elegant 

 creatures of a brilliant translucent green hue, which are 

 gracefully gliding about. They are of the genus Euglena, 

 so called because each is furnished with a very conspicuous 

 spot of a clear red hue, situated near the head, which 

 Ehrenberg, on account of its resemblance to the lowest 

 forms of eyes in the Rot if era, that are somewhat similar in 

 colour and appearance, pronounced to be an organ of 

 vision. More recent physiologists, however, doubt the 

 correctness of the conclusion. 



The animals are of several kinds. The most numerous 

 is an active little thing of about ^J-oth of an inch in length 

 when extended, though from its extreme versatility it is as 

 difficult to assign to it a definite size as a definite shape. 

 It seems to be the E. sanguinea, so called because it is 

 said to occur sometimes of a deep red hue, and in such 

 vast profusion as to give the waters the appearance of 

 blood. I have never seen it, however, other than as it 

 now appears, rich emerald green in the body, with the two 

 extremities perfectly clear and colourless. I might, per- 

 haps, describe its ordinary form as spindle-shaped, with a 

 pointed tail, and a blunt, rounded head ; but it is remark- 

 able for the variableness of its shape. It is capable of 



