COPROMONAS 



37 



The gametes (Fig. 16, 6) are to all appearance ordinary individuals : 

 they may happen to be slightly different in size (e.g. as in Fig. 16, 7) but 

 this appears to be purely a matter of chance. They become attached 



by their flagellar ends, 

 one flagellum is drawn 

 in and the bodies of the 

 two individuals gradu- 

 ally undergo a process of 

 complete fusion (Fig. 16, 

 7 to 10). While this is 

 taking place the nucleus 

 of each individual divides 

 into two (Fig. i6 ; 7) one of 

 the two daughter nuclei 

 degenerating : here we 

 have clearly a matura- 

 tion process comparable 

 with that of Actino- 

 sphaerium (p. 30). In 

 the case of Actlno- 

 sphaerium a second 

 nuclear division of this 

 kind took place and 

 in Copromonas this is 

 apparently represented 

 by the extrusion of one 

 or more small granules 

 of nuclear material from 

 the nucleus (Fig. i6 ; 8). 

 The two nuclei having 

 thus prepared them- 

 selves they approach 

 one another and fuse 

 together (Fig. 16, 10 to 

 n) to form the single 

 nucleus of the zygote. 



The process of syngamy is followed by encystment, either directly 

 (Fig. 16, n) or after a period during which the Copromonas swims 

 about and undergoes fission in the ordinary manner (Fig. 16, short circuit 

 from 9 to 5). The encysted stage here as in other Protozoa is a device 

 for getting through unfavourable conditions. During it the Copromonas 



FIG. 1 6. 



Diagram illustrating the life-history of Copromonas (after 

 Dobell, from Lectures on Sex and Heredity by Bower, Graham 

 Kerr and Agar). The upper circle of figures (i to 5) illustrates 

 the process of reproduction, the lower circle (5 to 12) that of 

 syngamy. 



