INFUSORIA. 445 



clear and colourless. I miglit perhaps describe ita 

 ordinary form as spindle-shaped, with a pointed tail, 

 and a blunt, rounded head ; but it is remarkable for the 

 variableness of its shape. It is capable of assuming an 

 appearance verj diverse from what it had half a minute 

 before, so that you would hardly identity it, if you 

 were not watching its evolutions. Whether this ability 

 to prove an alias be at all dependent on the remarkable 

 clear-headedness of the subject, I leave for you who are 

 skilled in metaphysics to determine. Away they go 

 tumbling over and over, revolving on the long axis as 

 they proceed, which they do not very rapidly, with the 

 blunt extremity forward. 



Here is another form, a little larger than the former, 

 but mucli more slender; yet from the slowness and 

 steadiness of its movement more easy of observation. It 

 is named E. acus^ or '' the Needle Euglena." This is 

 an animalcule of great elegance and brilliance ; its 

 sparkling green hue, with colourless extremities, and its 

 rich pale crimson eye, are very beautiful. It commonly 

 swims extended, with a slow gliding motion, turning 

 round on its long axis as it proceeds, as may be distinctly 

 seen by the rotation of certain clear oblong substances 

 in its body. These then are seen not in the interior, 

 but near the surface, as they would appear if imbedded 

 in the flesh around a hollow centre. The interior is 

 probably not hollow, but occupied with pellucid sarcode. 

 These were assumed by Ehrenberg, but on no adequate 

 grounds, to be organs connected with reproduction. 

 They vary in number in different individuals, and 

 those which contain the greatest number are thereby 

 more swollen. Tiiey appear to be separated into two 

 series, one anterior, the other posterior. The animal is 



