THE OPALINID CILIATE IXFUSORTAXS. 435 



most observers believe, or tactile or<^ans (Tiistkorperclien) as Stein 

 thought' [apparently they are nutritive plastids]. Opalinids on a 

 microscope slide are disturbed by and retract from strong light [an 

 observation not confirmed, so far as the author of this volume- knows]. 

 Contractile vacuole wanting in most Opalinids [the exceptions, in 

 his meaning, being, of course, of genera not to-day classed as Opali- 

 nidae]. No mouth or anus or digestive chamber. No reserve nucleus 

 (Reservekern) [micronucleus (?), not true of some of the genera 

 then classed with, but now removed from the Opalinidae]. Nuclei 

 of multinucleated species passive during body division. Fission 

 transverse, oblique or longitudinal. Zeller's studies upon reproduc- 

 tion and life history are described rather fully. 



Mengarini (189G) says that in OpaJ'ma [species?] from Rana 

 [species?] the pellicle serves as an osmotic membrane. Observations 

 and experiments are reported. 



Tonniges (1898). In the author's previous reference to this paper 

 (Metcalf, 1909) mention was omitted of Tonniges' definite denial of 

 the interpretation of longitudinal fission as conjugation, as some had 

 claimed, and of any occurrence of conjugation during the multi- 

 nucleated stage of the life cycle. Tonniges says that during encyst- 

 ment the several nuclei fuse " unter sehr,bemerkenswerthen Erschein- 

 ungen" [not describ'^l], so that the individuals which hatch from 

 the cysts in the tadpole are uninucleated [not confirmed by my obser- 

 vations], and these uninucleated individuals conjugate within the tad- 

 pole alimentary canal [no description of the process or of the appear- 

 ance of the gametes or zygotes]. Succeeding conjugation, there be- 

 gins active multiplication by longitudinal and transverse fission and 

 by budding. Transverse division is described fully. The products 

 of such division are sometimes unequal in size. AVhen the disparity 

 is great the process may be termed budding. Longitudinal and 

 multiple division are also described. The divisions of the nuclei 

 have no constant relation to the divisions of the body, and from this 

 fact the conclusion is drawn that the divisions of the nuclei are auto- 

 matic and without control from the cell body. [TTpon this point see 

 Hegner and Hsiang-Fong Wu (1921).] 



Schweier (1900) gives an identification table for the species raiui- 

 ru?n, ohtngona^ dimidiata, fava, int est in alls, and rmidatn, with 

 descriptions, figures, literature lists, and synonymy for each species. 



Entz (1901 and 1904) says that Opalina ranarum, through most 

 of the year, shows similar size, division being infrequent. The last 

 of April or the first of May occurs a mania for division, both trans- 

 verse and " oblique," until i or 2 nuclei [Metcalf, 1 to 12] are present 

 in each small individual, when encystment occurs. The cysts pass 

 with the feces of the host into the water and are taken with the food 



