74 



PROTOZOOLOGY 



How are these organelles formed? Tonniges (1914) believes that 

 the trichocysts of Frontonia leucas originate in the endosomes of the 

 macronucleus and development takes place during their migration 

 to the ectoplasm. Brodsky (1924) holds that the trichocyst is com- 

 posed of colloidal excretory substances and is first formed in the 

 vicinity of the macronucleus. Chatton and Lwoff (1935) find how- 



Fig. 22. Electronmicrographs of extruded trichocysts of Paramecium, 

 a, dried and stained with phosphotungstic acid, XI 1,000 (Jakus); b, a 

 similarly treated one, X 15,000 (Jakus); c, shadow-cast with chromium, 

 X 16,000 (Jakus and Hall). 



ever in Gymnodinioides the trichocysts are formed only in tomite 

 stage and each trichocyst arises from a trichocystosome, a granule 

 formed by division of a kinetosome (Fig. 23, a-c). In Polyspira, the 

 trichocyst formation is not confined to one phase, each kinetosome 

 is said to give rise to two granules, one of which may detach itself, 

 migrate into other part of the body and develops into a trichocyst 

 (d). In Foettingeria, the kinetosomes divide in young trophont stage 

 into irichitosomes which develop into trichites (e). The two authors 

 note that normally cilia-producing kinetosomes may give rise to 



