Phylum Protoplasta [ 203 



found that the two halves of the spindle swing apart as the centrosomes move apart 

 like the legs of a compass being extended. There is no doubt that Endamoeba and 

 Entamoeba are generically distinct. 



Endolimax, lodamoeba, and Councilmania occur chiefly in vertebrates and include 

 species commensal in man. A refined technique is required to discern the characters 

 by which they are distinguished from Entamoeba. Karyamoebina Kofoid and Swezy 

 (1924, 1925,) another commensal in man, resembles Vahlkampfia in details of the 

 mitotic process, and probably does not belong to the present group. Hydramoeba, 

 usually listed in the present family, is not an entozoic organism, but a predator on 

 Hydra. 



Family 6. Labyrinthulida [Labyrinthuhdae] Haeckel ex Doflein Protozoen 47 

 (1901). There is a single genus Labyrinthula Cienkowski, and probably only one 

 species, L. macrocystis, parasitic in green and brown algae and in the marine seed 

 plant Zostera. The uninucleate cells are spindle-shaped. These cells send out from 

 one or both ends fine filaments which writhe in the water. The filaments from differ- 

 ent cells coil together and produce "tracks" along which the cells glide. The tracks 

 form a network on which the cells may be scattered or gathered into clusters; or the 

 cells may abandon their tracks and generate new ones. The nature of the tracks is 

 not clear. Possibly they are pseudopodia, on which the cells move by absorbing them 

 at one end while generating them at the other. Young (1943) found Labyrinthula 

 remarkably indifferent to variations in temperature, reaction, and salinity. 



Family 8. Guttnlinacea [Guttulinaceae] Berlese in Saccardo Sylloge 7: 325 (1888) 

 Tribe Dictyosteliaceae Rostafinski Vers. 4 (1873). Sorophoreen with families Gut- 

 tulineen and Dictyostcliaceen Zopf Pilzthiere 131-134 (1885). Families Guttulineae 

 and Dictyosteliaceae Berlese op. cit. 451. Sappiniaceae Olive in Proc. American Acad. 

 37: 334 (1901). Families Sappiniidae, Guttulinidae , and Dictyostelidae Doflein 

 1909. Family Acrasidae Poche in Arch. Prot. 30: 177 (1913). Suborder Acrasina 

 Hall Protozoology 228 ( 1953 ) . Amoeboid cells predatory on bacteria and other scraps 

 of organic matter, in air on moist surfaces, commonly on dung. The cells are capable 

 of assembling and moving and going into a resting stage in unison. These organisms 

 have generally been included among the Mycetozoa; the resemblance is superficial. 



More recently than Olive, Raper (1940) and Bonner (1944) have surveyed the 

 group and studied the behavior. Three families have been maintained, but one appears 

 sufiicient to accommodate the seven genera and approximately twenty species. 



Cells of Sappinia are binucleate. They do not necessarily assemble in clusters; a 

 single cell may secrete a stalk, by which it is raised into the air, where it rounds up 

 and becomes dry. Alternatively, small numbers of cells may assemble and secrete a 

 common stalk. The dry cells are "pseudospores" : they are capable of resuming ac- 

 tivity without casting off a wall. Hartmann and Nagler (1908) described a peculiar 

 sexual process in Sappinia diploidea. 



Guttulina and Guttulinopsis produce larger clusters of resting cells than Sappinia 

 does; in Guttulina the resting cells are said to be walled spores. 



Acrasis produces fruits, solitary or clustered, of the form of uniseriate rows of spores 

 terminal on stalks consisting of rows of dead cells. 



Distyostelium produces fruits consisting of a column of dead cells bearing a globu- 

 lar cluster of spores; Polys phondylium and Coenenia produce slightly more elaborate 

 fruits of the same general nature. In Dictyostelium, Raper and Bonner saw that the 

 amoeboid active cells, having devoured the available food, gather into a disk-shaped 

 mass which may exceed a millimeter in diameter. Wilson (1953) found syngamy, 



