124 



PROTOZOA 



CHAP. 



irregularly and at intervals, resolving finally into 1 -nucleate frag- 

 ments, which encyst and pass into the water. When swallowed 

 the cyst dissolves, its contents enlarge, and ultimately assume 

 the adult form. 1 



Maupasia has a partial investment of cilia, a single long 

 flagellum and mouth, a contractile vesicle, and a single simple 

 nucleus. It seems to find an appropriate place near the two 

 above groups, though it is free, and possesses a mouth. 



Among the Euglenaceae, Euglena viridis is a very common 



Fig. 42. 



Longitudinal Fission of Eutreplia viridis (Euglenaceae), showing chloroplasts, 

 nucleus, and flagella arising from pharynx-tube. (After Steuer.) 



form, giving the green colour to stagnant or slow-flowing ditches 

 and puddles in light places, especially when contaminated by a 

 fair amount of dung, as by the overflow of a pig-sty, in company 

 with a few hardy Eotifers, such as Hydatina senta (Vol. II. Fig. 

 106, p. 199) and Brachionus. Euglena is about 0*1 mm. in 

 length when fully extended, oval, pointed behind, obliquely trun- 

 cate in front, with a flagellum arising from the pharyngeal pit. 

 It shows a peculiar wriggling motion, waves of transverse con- 

 striction passing along the body from end to end, as well as 

 flexures in different meridians. Such motions are termed 

 " euglenoid." The front part is colourless, but under a low 



1 Bezzenberger has given an analytical table of the eleven known species of the 

 genus Opalina in Arch. Protist. iii. 1903, p. 138. 



