SUBKINGDOM PROTOZOA. 



23 



which it remains until the food-matter has been thoroughly 

 digested, when the cyst is thrown off together with the empty 

 diatom shells and the animal again becomes active. 



Plentiful nutrition and reproduction by division (including 

 under this term the various modifications of fission) are 

 related to a certain extent, and it is easy to understand why 

 the two processes of encystment and spore-formation should 

 be associated together. The Heliozoan Vampyrella (Fig. 

 10, A) feeds in its active condition on diatoms, and especially 

 on a stalked form, Gomphonema. After having digested the 

 contents of the diatom frustules which it engulfs it pushes 



A 



FlG. 10. Vampyrella (from HAECKEL after BUTSCHLI). 



A. Vampyrellu feeding upon the stalked diatom Gomphonema. 



B. Vampyrella eucysted upon the stalk of the diatom. 



them aside and encysts itself upon the stalk previously occu- 

 pied by them. Within the cyst the animal divides into four 

 spores (Fig. 10, B}, each of which escaping from the cyst 

 becomes a new Vampyrella. 



Among the Radiolaria spore-formation seems to be the 

 most usual method of reproduction, and a complication occurs 

 among them in that spores of two kinds may be formed. In 

 some cases the spores, which are formed from the intracap- 

 sular protoplasm, are all equal in size (isospores], while in 

 others some of the spores may be large (macrospores) and 

 others small (microspores). Both macrospores and micro- 

 spores may be formed in the same individual, or each indi- 

 vidual may produce only one of the two forms. In such cases 

 it is easy to determine whether one has to do with macro- 

 spores or isospores, which closely resemble each other in size, 



