22 BEITISH PRJiSHWATER HBLIOZOA. 



diameter of nucleus about one quarter the diameter 

 of the body : length of pseudopodia variable, usually 

 one and a-half times the diameter of the body. 



Habitat. — In still waters amongst aquatic vegetation. 



Distribution. — General in Great Britain and Ireland. 



The nucleus in this species is of large size with 

 a clear central portion and the periphery with a 

 granular appearance. The enclosing membrane is of 

 appreciable thickness. Surrounding the nucleus is a 

 zone of clear cytoplasm, through which may be traced 

 the pseudopodial axes which have their origin close 

 to the nuclear membrane. 



The processes of reproduction have been described 

 on p. 10; when encystment takes place an outer test 

 is formed of minute silicious scales cemented together, 

 inside which is a smaller membranous sac into which 

 the animal contracts ; the outer test has a mucilaginous 

 coating for purposes of attachment. When the period 

 of encystment expires the two envelopes are ruptured 

 and the animal emerges in an amoeboid form which 

 soon protrudes flagella-like pseudopodia and exhibits 

 a general likeness to a Giliophrys ; at this stage multiple 

 division may take place giving rise to colonies of small 

 individuals ; these colonies may quickly break up or 

 may be more or less persistent. 



ActinopJir//s as a rule is carnivorous but algee also 

 serve it for food (Text-fig. 182) ; its usual prey consists 

 of ciliates and small rotifers which it entangles in its 

 pseudopodia and appears to numb or kill by the emission 

 of some poisonous secretion ; during this process the 

 pseudopodia are often bent over and draw the cap- 

 tured animal to the periphery of its body where it is 

 ingested and enclosed in a digestive vacuole, which 

 in this species is usually voluminous, especially when 

 as sometimes happens two or three individuals form a 

 group with a single vacuole in common. 



Green algse or zoochlorell^ are seldom found living 

 symbiotically in A. nol although Leidy records several 



