2 6? 
in size takes place, and eventually they become spherical 
and divide into a number of segments (schizonts). 
According to some observers segmenting forms are only 
found in the spleen. 
(ii) Sexual Forms .—Free in the plasma, twelve 
to fifteen ^ long. These are male and female, and are 
characterized by the same general differences as other 
gametes ; the male mikrogametocyte is slender and 
finely granular ; the female makrogametocyte is fat 
and coarsely granular. 
(iii) A mikrogamete in the form of a small mass 
of chromatin separates off and fertilizes the (now) 
makrogamete. 
Fig. 81. H. ranarum {or Drepanidium ranarum) young form, 
Gametes free in the Plasma , and Fission forms in 
Spleen. {Partly after Minchin) 
(iv) A zygote results, which is at first motile. 
This becomes encysted as the 
(v) Oocyst, which is found in the epithelial cells 
of the intestine. This passes out eventually in the 
faeces of the frog. Sporoblasts are formed as in the 
malarial cycle, and from these result 
(vi) Sporozoits .—These would gain access to a 
fresh frog which had swallowed an oocyst. 
According to Billet development takes place in 
leeches of the genus Helohdella. 
