PROTOZOA AND OTHER ANIMALS 915 



have often been thought to exert direct or indirect pathogenic action, 

 but proof that they are more than ectocommensals is lacking. Kidder 

 and Summers (1935) distinguished several species on the carapaces of 

 three species of Orchestiidae from beaches in the region of Woods Hole; 

 they noted that no similar ciliates were found free in the sand or sea- 

 weeds, and the commensals lived only a short time when separated from 

 their hosts. C. capncinus Penard, 1922, and C. granulata Penard, 1922, 

 are commensal on Asellus and Gammarus, and C. porcelliotiis occurs in 

 the gill cavities of the terrestrial isopod PorcelUo sp. (Dogiel and Furs- 

 senko, 1921). In aquatic hosts, transmission would take place through 

 the water; in C. porcelUonis it must be through survival, at least for a 

 short period, in moist soil. 



A number of hymenostomes of the new genus Allosphaerium were 

 also described by Kidder and Summers (1935) from the one species of 

 Talorchestia and two of Orchestia that they examined at Woods Hole, 

 Massachusetts. They remarked, concerning the ectocommensal holotrichs 

 of amphipods and isopods, that the external characteristics are singularly 

 well adapted to the environment. 



They are all small flat forms and possess ventrally placed thigmotactic cilia 

 {Chilodonella, Trochilia, Allosphaerh/m) . When one considers the forces, 

 mainly in the form of water currents, to which they must be subjected and 

 which would tend to effect their removal from the carapace of their various 

 hosts, it is seen that the flatness of their bodies and the adhesive powers of 

 their ventral cilia are of absolute necessity. Existing under the same conditions, 

 it is perhaps not surprising that representatives of two orders of ciliates ex- 

 hibit convergence to such a degree as to render them practically indistinguish- 

 able one from the other except under extreme magnifications. 



Genera with free-living Trichostomata and Hymenostomata include 

 only a few commensal and parasitic species, but there are numerous 

 genera all members of which are associated with animal hosts. Frontonia 

 branchiostomae was found in abundance at Banyuls-sur-Mer by Cod- 

 reanu (1928) in the atria of most specimens of Branchiostoma lanceo- 

 latum exceeding 3 cm. in length. The genus Glaucoma has been dis- 

 cussed at length under facultative parasitism. Uronema rabaudi was be- 

 lieved by Cepede (1910) to be a coelomic parasite of Acartia claus'i and 

 ClausJd elongata, in the empty carapaces of which it was observed. With- 

 out free-living congeners, but similar enough to Uronema to have been 

 put in that genus by Butschh (1889) and Cuenot (1891), is Philaster 



