MORPHOLOGY 65 



Although the trichocyst was first discovered by Elhs (1769) 

 and so named by Allman (1855), nothing concrete is yet known as 

 to their function. Ordinarily the trichocysts are considered as a de- 

 fensive organella as in the case of the oft-quoted example Parame- 

 cium, but, as Mast demonstrated, the extruded trichocysts of this 

 ciliate do not have any effect upon Didinium other than forming a 

 viscid mass about the former to hamper the latter. Penard con- 

 siders that some trichocysts may be secretory organellae to produce 

 material for loricae or envelope, with which view Kahl concurs, as 

 granular to rod-shaped trichocysts occur in Metopus, Amphileptus, 

 etc. Klein has called these ectoplasmic granules protrichocysts, and 

 in Prorodon, Kriiger observed, besides typical tubular trichocysts, 

 torpedo-like forms to which he applied the same name. To this 

 group may belong the trichocysts recognized by Kidder in Con- 

 chophthirus mijtili. The trichocysts present in certain Cryptomonad- 

 ina (Chilomonas and Cyathomonas) are probably homologous with 

 the protrichocysts. The pigments, which give a beautiful coloration 

 to certain ciliates such as Stentor and Blepharisma, are said to be 

 lodged in the protrichocysts. 



Hold-fast organellae 



In the Mastigophora, Ciliophora, and a few Sarcodina, there 

 are forms which possess a stalk supporting the body or the lorica. 

 With the stalk the organism is attached to a solid surface. In some 

 cases, as in Anthophysis, Maryna, etc., the dendritic stalks are 

 made up of gelatinous substances rich in iron, which gives to them a 

 reddish brown color. In parasitic Protozoa, there are special or- 

 ganellae developed for attachment. Many genera of cephaline 

 gregarines are provided with an epimerite of different structures 

 (Figs, 208-210), by which the organisms are able to attach them- 

 selves to the gut epithelium of the host. In Astomata, such as Into- 

 shellina, Maupasella, Lachmannella, etc., simple or complex pro- 

 trusible chitinous structures are often present in the anterior region; 

 or a certain area of the body may be concave and serves for ad- 

 hesion to the host, as in Rhizocaryum, Perezella, etc.; or, again, 

 there may be a distinctive sucker-like organella near the anterior 

 extremity of the body, as in Haptophyra, Steinella, etc. A sucker is 

 also present on the antero-ventral part of Giardia intestinalis. 



In the Myxosporidia and Actinomyxidia, there appear, during 

 the development of spore, 1-4 special cells which develop into 

 polar capsules, each, when fully formed, enclosing a more or less 

 long spirally coiled delicate thread, the polar filament (Fig. 259). 



