50 



ZOOLOGY 



SECT. 



undergo a process of division resulting in the formation of a number 

 of small bodies or spores which, when mature, are set free by the 

 rupture of the wall of the cyst. Each of these may develop directly 

 into the adult form. But in some cases it has been found that on 

 becoming free from the cyst they coalesce in pairs either with one 

 another or with similar bodies from other cysts. To such a 



FIG. 33. Trichospaerium sieboldii. 1, Adult of "A" form; 2, its multiplication by 

 fission and gemmation ; 3, division into amoeboid spores ; 4, development of one of these 

 into " B " form (5) ; 6, its multiplication by fission and gemmation ; 7, its division into 

 numerous minute bodies ; 8, discharge of these as biflagellate gametes ; 9, 10, copulation, 

 more highly magnified ; 11, zygote ; 12, transition towards " A " form. (After 

 Schaudinn.) 



coalescence, which extends to the two nuclei as well as the cyto- 

 plasm, the term copulation is applied the two copulating bodies 

 being gametes and the body resulting from the union a zygote. This 

 is the simplest form of sexual reproduction. A slight complication 

 is introduced when, as in Amoeba blattce, there are two sets of gametes 

 to be distinguished a larger and a smaller and copulation 



