934 PROTOZOA AND OTHER ANIMALS 



occur on Protozoa or other invertebrates. They are provided with thigmo- 

 tactic ciha; and they show a series in the evolution of thigmotacticism, 

 in the course of which there is developed a penetrative and absorptive 

 organelle, and in the regression of body ciliature. Chatton and Lwoff 

 (1923a) described Thigmophyra, which was later (1926) placed in 

 a fourth family, Thigmophryidae. Thigmophrya, it was stated, closely 

 resembles Conchophthirus; but, unlike Conchophth'nus, it possesses a 

 well-defined thigmotactic area identical with that of other Thigmotricha. 

 Kahl (1934) summarized the characteristics of the suborder Thigmo- 

 tricha and included in it the Conchophthiridae, which he had formerly 

 (1931) treated in the suborder Trichostomata, and which Chatton and 

 Lwoff (see 1937) evidently did not intend to include in their group. 



Though Calkins (1933) considered adaptations to parasitism in the 

 thigmotrichs as a group, he included most of the genera in the Tricho- 

 stomata, including the Ancistrumidae which Kahl (1931) had put in 

 the Hymenostomata. Calkins, on the other hand, separated Hemispeira 

 from other Ancistrumidae, putting it in the Hymenostomata. Whether 

 the Thigmotricha constitute a homogeneous group may be questionable 

 ( Faure-Fremiet, 1924, p. 7); but for consideration of the ethological 

 relationships and adaptations to symbiotic existence, the object of interest 

 in this account, it is convenient to treat them together. 



Most Conchophthiridae occur in the mantle cavity of Pelecypoda, 

 both marine and fresh-water species. Andreula antedoms (Andre) Kahl 

 {=^Conchophthirus antedonis Andre) occurs abundantly in the alimen- 

 tary canal of a crinoid echinoderm; and Uyemura ( 1934) described as C. 

 striatus a ciliate in the intestine of several sea urchins of Japan. Myxo- 

 phyllum steenstrupii (Stein) lives in the slime covering the body of a 

 variety of land pulmonates. The species of Morgania Kahl and all ex- 

 cept the one species of Conchophthirus Stein (the original spelling by 

 Stein, 1861, not " Concho phthmus" as given by Strand, 1928) men- 

 tioned above are restricted to bivalves. 



The most detailed studies of the genus Conchophthirus are contained 

 in several articles published in 1933-34 by Kidder and by Raabe. Uye- 

 mura (1935) found three species in great abundance in a fresh-water 

 mussel of Japan, Anodonta lauta. There is no doubt that in all parts of 

 the world certain lamellibranchs will be found abundantly infected with 

 these commensals. Only a beginning has been made in their study, as 



