ACTINOPHRVS. 



phrys feeds are paralysed when they come in contact with 

 the pseudopodia. 



The body consists of ectoplasm and endoplasm. The 

 ectoplasm is a thick external layer closely packed with 

 large vacuoles, which are non-contractile and contain a 

 clear fluid. But food vacuoles are formed as in other 

 Protozoa, and there is also a single contractile vacuole. 

 The endoplasm forms the central mass. It is not 

 vacuolated, and contains the large, centrally placed nucleus. 



Life history. 

 An Actinophr-ys may 

 withdraw its pseudo- 

 podia and divide 

 into two, with or 

 without the forma- 

 tion of a cyst. A 

 number of indi- 

 viduals may unite 

 for a time by the 

 ectoplasm alone, 

 and separate with- 

 out any nuclear 

 fusion having taken 

 place (plastogamy). 



FlG. 36. Actinophrys sol (Sun-animalcule). 

 After Grenacher. 



., nucleus ;./.>., food vacuole; v. t contractile 

 vacuole ; PS., pseudopodium. 



But Schaudinn has 



described a true 



sexual process 



which offers an 



interesting analogy 



to the processes of maturation and fertilisation in the 



higher animals. 



A number of individuals become joined up in a common 

 gelatinous cyst. Each loses its pseudopodia and forms a 

 membranous cyst. These cysts become associated in pairs. 

 The nucleus of each cyst divides mitotically and a polar 

 body is extruded from each, after which the nucleus 

 returns to the resting condition. The cysts now fuse in 

 pairs, with complete and intimate union of their nuclei 

 and cell-bodies. The zygote so formed rests for a short 

 period, then divides up into two daughter cysts from which 

 emerge two new individuals of Actinophrys. 



