

THE SARCODINA 93 



vidual remaining in the old quarters (Microgromia, Fig. 51). A more 

 complicated process is found in the majority of fresh-water shelled 

 Rhizopoda, where division is practically a form of budding, the plasm 

 growing out of the original shell mouth and forming a small bud on 

 the outside. This bud grows until it has reached its definitive size 

 (usually about that of the original cell), when the shell-coating for 

 the new individual is deposited. The building material for the shell 

 of the daughter-individual is formed within the protoplasm of the 

 maternal cell. If regular plates of silica or chitin, 1 these plates 

 are secreted long before division and stored up in the protoplasm 

 which surrounds the nucleus (Euglypka, Quadruld). If quartz crys- 

 tals, or any other foreign bodies, these particles are picked up and 

 stored in a similar manner, to be used later for the test of the daugh- 

 ter-cell. When the bud has reached a certain size, the plates or par- 

 ticles which are to form the shell move out through the mouth-opening 

 of the parent shell and form around the protoplasm of the bud. In 

 the meantime the nucleus undergoes division, and, in the case of 

 Euglypha at least, the daughter-nucleus is the last element to leave 

 the parent organism (see Fig. 23, p. 55). 



Heliozoa, when preparing for division, become soft, draw in their 

 pseudopodia, and round out into a perfect sphere, after which the 

 nucleus divides by mitosis (Actinophrys), and the cell slowly separates 

 into two parts. In Nuclearia, division is very rapid, the entire 

 process taking place within one minute. In many cases, division is 

 incomplete, the individuals remaining attached to form colonies 

 (Heterophrys, Spharastrum, Raphidiophrys\. 



Swarm-spore formation is widely distributed among the Sarcodina, 

 usually taking place under the protection of a cyst. The parent 

 organism divides into a number of daughter-cells, each containing 

 a part of the original nucleus, and each provided with pseudopodia or 

 flagella. A good illustration is seen in Paramceba Eilkardi, one of 

 the. naked Rhizopoda (Schaudinn, '96). The animal is flat and 

 discoid, with short, lobose, finger-formed pseudopodia, and varies in 

 size from 10 to 90 //. (Fig. 52). It usually increases by simple 

 division, but at the end of its vegetative life it encysts, and the plasm 

 divides into a number of pieces. Fragmentation of the nucleus is 

 preceded by division of a peculiar cytoplasmic body, which Schaudinn 

 terms the Nebenkorper. The contents of the cyst break into as many 

 pieces as there are divisions of the Nebenkorper. Finally, each 

 fragment of the protoplasm, containing a part of the original nucleus 

 and of the cytoplasmic Nebenkorper, develops two flagella and breaks 

 out of the cyst as a swarm-spore (J3, C, D}. The young organisms 

 swim about in this condition for some time, and may increase by longi- 

 tudinal division until, finally, losing their flagella, they develop pseudo- 



