STUDIES OF NON-PARASITIC PROTOZOA 11 



animalcule sometimes attains 2 millimetres in diameter, and it exists 

 in two distinct forms, which are the expression of an alternation of 

 generations. In both forms the body is invested in a gelatinous 

 sheath. In the sexually produced individual, or amphiont (Fig. 2 ; 7) 

 this sheath is studded with short rods which are composed of mag- 

 nesium carbonate, and cause this genus, though classed with the 

 naked amoebae (gymnamoebida), to approach the shelled amoebae 

 (thecamoebida), such as Arcella and Difflugia, common in fresh-water 

 ponds. 



In the asexually produced individual (monont, Fig. 2 ; 5) the 

 sheath lacks the rods. Both amphiont and monont are capable 

 of protruding slender processes (pseudo- or lobo-podia) through the 

 sheath, which may present thickenings at the points at which per- 

 forations exist. These lobopodia are used for locomotion, which 

 is extremely slow, about 10 //. to the minute. Food, such as 

 diatoms, and foreign bodies, such as grains of sand, etc., are held 

 by the lobopodia and very slowly incepted. 1 An interesting example 

 of commensalism is also furnished by this organism. When food is 

 plentiful a flagellate (Cryptomonas Brandti, Schaudinn) lives in the 

 protoplasm appearing as brown cells. When food is withheld these 

 escape from the Trichosphtzrium as monads, provided each with two 

 flagella, Plastogamy,or the formation of adhesion-colonies (Fig. 2; 72), 

 is observed in this as it is in other amoebae. The amphiont is capable 

 of two different modes of multiplication : vegetative or ambulant 

 subdivision (Fig. 2 ; 1a, 76), and multiple asexual subdivision in a 

 resting state conitomy or schizogony (Fig. 2 ; 2). In ambulant 

 subdivision the multinucleated organism, its lobopodia withdrawn, 

 simply divides by constrictions, which include the sheath, into two 

 or more parts. Before conitomy occurs all foreign materials are 

 expelled and the lobopodia are withdrawn ; the body subdivides into 

 a number of uninucleated gymnospores, which escape by rupture of 

 the sheath, which consists of the maternal rod-studded envelope. 



1 This process is described as follows : ' If the organism comes against some 

 foreign body the latter is held between the pseudopodia and the sticky surface of 

 the sheath. The protoplasm of the amceba rolls over the body like a ball of thin 

 paste, into the interior of which the body is pressed.' 



