MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 473 



r-. . 





nX*' 



Fig. 192; Stentor, Calyptotricha, etc.) or spheroidal masses (Ophry- 

 il in in) are sometimes found, but cups or "houses" into which the 

 organisms withdraw (Cothurnia, Vaginicola, Folliculina, etc.) or by 

 which they are supported (Acinetidae, Discophryidae) are more 

 common. Tightly-fitting membranes with sculptured interlocking 

 plates of chitin or pseudochitin are present 

 in Cole})* and Tiarina (Fig. 73, p. 136). 



The endoplasm is finely alveolar and much 

 more fluid than the more highly differentiated 

 cortex or ectoplasm. The endoplasm reveals 

 different types of refringent granules during 

 life, some of which have been identified as 

 excretory granules (Prowazek, Nirenstein), 

 others as mitochondria (Faure-Fremiet, 

 Cowdry) and others as belonging to the 

 Golgi apparatus (Nassonov). In addition to 

 these, reserves of food substances, kinetic 

 elements and metaplastids of different kinds, 

 with the nuclei make up the substance of the 

 endoplasm. 



Metaplastids are numerous and widely dis- 

 tributed. Of these trichites, trichocysts and 

 "pharyngeal baskets" are the most charac- 

 teristic. Trichites are elongate, slender rods 

 usually surrounding the mouth in gymno- 

 stomes and are generally interpreted as organs 

 of support or protection. They are not lim- 

 ited to the oral region, however, and in some 

 forms provide a protective cuirass about the 

 posterior region (Strombidium) . The oral 

 trichites are numerous and closely applied and 

 in some cases form a continuous and smooth 

 tube extending deep in the endoplasm (some 

 Nassulas, Orihodon, etc.). Trichocysts are 

 shorter and more conspicuous; formed in the 

 endoplasm they assume a radial position 

 in the cortex and may cover the entire sur- 

 face (Paramccimn, Fig. 193; Frontonia, etc.) 

 or may be limited to certain regions (Dileptus 



proboscis, Fig. 194). In a moving Actinobolina they are arranged 

 as in Paramecium, but in a quiescent individual each trichocyst is 

 carried out at the end of a long tentacle which this interesting ciliate 

 has the power to protrude for feeding purposes (Fig. 91, p. 163). 



The function of the trichocysts is still in dispute (Visscher, 1923). 

 The substance of a trichocyst may be shot out in the form of a long 

 thread which hardens on contact with water. In such forms, repre- 



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' I 



Fig. 192.— Stichoiricha 

 secunda, a tube-dwelling 

 hypotrichous ciliate. 

 (Original, i 



