158 DESCRIPTION OF [Polygastrica. 



The tail is generally about the length of the body and 

 pointed; colour green. Group 74 represents two of these 

 creatures magnified 400 diameters. Rarely found with 

 any other species. I have taken them at Hampstead, but 

 not so frequently as the other species. Length 1-1 152nd 

 to 1 -864th. 



132. EUGLENA pleuronectes (Cercaria pleuronectes, M.) 

 The plaice- shaped Euglena. Body compressed, ovato-orbi- 

 cular, or in the form of a leaf; striated longitudinally; 

 colour green; tail pointed, one-third or one-fourth part 

 the length of the body, and colourless. Found in stagnant 

 water. Length 1-1 15 2nd to 1 -480th. 



133. EUGLENA longicauda. The long-tailed Euglena. 

 Body mostly stiff, compressed, illiptical and leaf-like ; 

 colour green; tail the length of the body, awl-shaped, 

 and colourless. Within this creature may often be seen 

 a yellowish -green mass of granules or ova. The very 

 delicate vibrating thread-like proboscis represented in the 

 figs. 75 and 76 originates from the more projecting part of 

 an indentation on the anterior edge of the body, and is 

 about two-thirds its length. This creature has the power 

 of twisting its body into a spiral form, as seen in fig. J5, 

 but not of contracting it. It swims freely, and mostly 

 with a vibratory motion, occasioned by the action of the 

 proboscis. Found in fresh water, amongst conferva, and 

 with the Bacillaria. Length l-480th to 1-1 20th. 



134. EUGLENA triquetra. The three-sided Euglena. 

 Body leaf-shaped, three-sided, oval-keeled ; colour green ; 

 tail shorter than the body, and colourless. See fig. 77- 

 Found amongst lemna. Length 1-5 80th. 



135. EUGLENA acus {Vibrio acus, M.) The needle- 



