92 THE PROTOZOA 



disintegrated, the digestible portions being transformed into a sort 

 of chyle which is distributed throughout the protoplasm. The gastric 

 vacuole with its undigested residue is gradually left behind like a 

 loaded contractile vacuole, until finally it is expelled to the outside 

 (Arnceba). The Sarcodina, apparently, digest mainly proteids, some 

 forms of starch, and fats remaining unchanged (Meissner, '88 ; Green- 

 wood, '80; Stole, '00). 



G. Reproduction 



The Sarcodina reproduce mainly by simple division or spore-for- 

 mation, either in the free state while active, or when quiet in the 

 encysted state. The simplest form, consisting of a mere bipartition 

 of the protoplasm and of the essential body-contents, occurs when the 

 body is so large that it becomes unwieldy and it divides from sheer 

 inertia. A well-known example is that of the division of Arnceba 

 polypodia {Dactylospkcera, F. E. Schultze). Here, as in all cell-divi- 

 sions, the nucleus divides first, the body then separating into two parts. 

 Simple division becomes more complicated when the organism is 



Fig. 51. — Microgrotnia sociatts Hert. [HERTWIG.] 

 Division takes place within the shell, and one of the daughter-individuals migrates, forming a 

 new shell. 



provided with an outer coating or test, although in the simplest of 

 such cases, where the coating is flexible and plastic, as in Vampyrella, 

 the process involves only the partition of the outer membrane. When 

 the outer covering becomes hard and firm by impregnation with chi- 

 tinous, silicious, calcareous, or horny materials, the operation is more 

 complicated. The organism, while still within the shell, may divide 

 by longitudinal division, one of the daughter- individuals then migrat- 

 ing from the parent shell and, after a longer or shorter time, settling 

 down and secreting a new shell for itself, the other daughfer-indi- 



