156 DESCRIPTION OF [Polygastrica. 



drical or spindle- shaped form, with the head greatly 

 rounded ; the tail is short, conical, and somewhat pointed. 

 Proboscis longer than the body in its extended condition. 

 When young, they are green, but when full grown, are of 

 a blood-red colour. The motion of this variform ani- 

 malcule is generally slow, and it sometimes revolves upon 

 its longitudinal axis in swimming. Its colour is not of a 

 fixed character, some being green, others spotted red and 

 green a mixture of both. This arises, according to Ehren- 

 berg, from the different condition of the ova at different 

 times, and which cover numerous granular round bodies, 

 supposed to be digestive cells. The thread-like proboscis, 

 which is a prolongation of the upper lip, and rather longer 

 than the body, is so delicate, as to require considerable 

 care in investigating it, and being retractile, will often 

 elude our observation. A little colouring matter in the 

 water will exhibit this organ in active operation, and it 

 may be distinctly seen in a single animalcule, in a dried 

 state, upon a plate of clear glass. The double appearance 

 of the organ in this species has been before noticed. 

 Ehrenberg conjectures that the miracle in Egypt, 

 recorded by the great lawgiver of the Jews, of turning 

 the water into blood, might have been effected by the 

 agency of these creatures, or by the Astasia hsematodes. 

 Figures 71 > 72, and 73, represent the creature in different 

 states. In the first, it appears elongated, and currents in 

 the water are shewn near the mouth. In the others, the 

 cilia-formed thread-like proboscis is seen. Found in 

 stagnant water ; often in great abundance on the surface of 

 ponds. Length l-300th to l-240th. 



127. EUGLENA hyalina. The crystal-like Euglena. 



