72 



THE LOBOSA 



formed by the trophochromidia of Difflugia as carbohydrate in 

 composition, but the crystalline and other bodies of Trickosphaerium, 



according to Schaudinn, give differ- 

 ent reactions. 



Vacuoles. In nearly all the 

 freshwater and marine Lobosa there 

 is at least one contractile vacuole. 

 In Pelomyxa and some of the Theca- 

 moebida, however, contractile vac- 

 uoles have not been found. The 

 endoparasitic Amoebida have no 

 contractile vacuoles. In addition 

 to the contractile vacuole numerous 

 non- contractile vacuoles containing 

 a fluid of unknown constitution 



A small portion of the ectoplasm of -i . i i i i 



PeZom W zapaZu*Ms, very highly magnified, but probably nearly pure water 



r.c, refringent proteid bodies; b, symbi- nrrnr in thp pnrlnn]im 



otic bacteria (Cladothrix) chr, scattered OCCU 



chromidia; v, water vacuoles. (After liott.) When a particle of food OCCUI'S 



in a non-contractile vacuole it is 



usually called a food-vacuole, and the fluid in such vacuoles has 

 been shown in some cases to be slightly acid in reaction and 

 probably contains a digestive ferment. 



In Arcella and in other Thecamoebida vacuoles containing a 

 gas are found within the shell. These vacuoles serve hydrostatic 

 functions. 



Reproduction Fission. Reproduction by fission has been 

 proved to occur a a- normal process in many of the genera of 

 Lobosa. In Amoeba and allied genera the result 

 of fission is a pair of equal -sized daughter 



A small portion of the ectoplasm of 



Fio. 8. 



Dactylosphaera polypodia, M. Schultze, in three successive stages of division. The stages 

 indicated occupied fifteen minutes, a, nucleus; b, contractile vacuole. (After F. E. 

 Schultze.) 



Amoebae. In Pelomyxa, Trichosphaerium, and probably in other 

 multi nucleated Gymnamoebida, fission may be unequal. 



In the Thecamoebida one of the individuals of the act of fission 

 retains the shell, and the other sooner or later forms a new shell 

 which is usually larger than that of the parent. 



