POLYMORPHISM AND LIFE-CYCLES 183 



protoplasmic body is a multinucleate plasmodium. There are two 

 forms of the adult the schizonts (agamonts), which are dis- 

 tinguished by the presence of rod-like spicules in the envelope 

 (Fig. 81, A) ; and the sporonts (gamonts), which have no spicules 

 (Fig. 81, F). The schizonts reproduce themselves either in the 

 free state or after encystment. In the free state the reproduction 

 is by simple or multiple plasniotoniy that is to say, by division of 

 the plasmodium into two or more portions. In the encysted con- 

 dition the schizonts divide by multiple fission into as many daughter- 

 cells as there are nuclei in the plasmodium (Fig. 81, B), and each 

 daughter-cell is set free as an amoebula (agamete), which may either 

 grow up into a sporont, or into a schizont which repeats the process 

 of multiplication by schizogony. 



The sporont may reproduce itself in the free state in the same 

 manner as the schizont, byplasmotonry, or it may become encysted, 

 and then it multiplies in a manner totally different from that seen 

 in the corresponding phase of the schizont. The nuclei of the 

 encysted sporont multiply rapidly by karyokinesis (Fig. 81, G) until 

 there are a very large number of minute nuclei ; very probably the 

 final divisions in this process of multiplication are reducing divisions. 

 The protoplasmic body then becomes divided up into as many 

 minute cells as there are nuclei, and each of the daughter-cells 

 acquires two flagella, and is set free as a flagellula or gamete 

 (Fig. 81 , H). The gametes, which are not differentiated in any way, 

 copulate with those derived from another sporont, and lose their 

 flagella (Fig. 81, / -L) ; the zygote is a small amoebula which grows 

 up into a schizont (Fig. 81, L, M, N, A). 



An alternation of generations similar to that of Trichosphcerium 

 occurs also in the Fora minif era (p. 234). Here the schizont contains 

 numerous nuclei, which multiply by fission as the animal grows, and 

 also chromidia ; it reproduces itself by a process of multiple fission, 

 breaking up into a number of amoebulae (agametes), each with a 

 nucleus and chroniidia. The amcebulse creep out of the old shell, 

 which is abandoned, and each amoebula secretes a shell for itself, 



FIG. 81 continue! : 



itself and grows, with multiplication of the nuclei (D and E) into the gamete- 

 producing form or sporont (F), similar in general structure to the schizont (A), 

 but without rods in the envelope ; the sporont may also multiply in a vegeta- 

 tive manner by simple or multiple fission, or it may form gametes in the 

 manner seen in G and H ; G, active multiplication of the nuclei of the sporont 

 to form a great number of very small nuclei, after which the body divides 

 up into as many minute cells as there are nuclei ; these cells are the gametes, 

 and each gamete acquires two flagella ; H, rupture of the envelope to set free 

 the gametes, which swarm out and conjugate ; /, conjugation of two gametes, 

 more highly magnified ; ./, after fusion of the bodies of the gametes the 

 flagella are thrown off ; K, fusion of the two pronuclei ; L, complete zygote, 

 which forms an envelope and grows, with multiplication of the nuclei (M, N) 

 into the schizont (^4), which was taken as a starting-point of the life-cycle. 

 After Schaudinn (146). 



