Opalina. 323 
figured, is not distinguished in the description from 0. dimidiata 
[which has the same shape but contains many nuclei. 
Dusarpin (1841) makes very brief reference to the Opalinas, 
giving an unrecognisable figure [probably not of an Opalina). 
MAX SCHULTZE (1851) says (p. 68) that it seems to him very 
probable that the Opalinas form no true independent genus, but 
are rather developmental stages or nurses (“Hntwicklungsstufen oder 
Ammen”) of other animals. |The word Ammen is difficult to under- 
stand in this connection.| He notes (p. 69) the absence of a con- 
tractile vacuole in O. ranarum. 
Perry (1852) correctly describes the form of O. ranarum from 
the alimentary canal of Rana temporaria. He says that the mouth 
and body cavity are scarcely recognisable; that the whole surface 
in life seems evenly ciliated, and that the longitudinal striation in 
dead individuals is due to delicate folds, not to cilia. The appearance 
of the waves of motion of the cilia is aptly compared to that of 
the waves which pass across a wheat field in the wind. No figures 
are given. Bursaria (Opalina| intestinalis is mentioned but not 
described. 
Stern (1856) mentions (p. 56) O. ranarum and also suggests that 
Bursaria intestinalis may be an Opalina. On p. 37 he diagnoses the 
genus Opalina (in the broader sense) saying that the cilia are in 
rows over the whole surface of the body, that these animals are 
distinct from all other Infusoria in having no mouth and therefore 
taking their nourishment in liquid form through the whole surface 
of the body; in having for the most part no contractile water 
vacuole; and in being often without nucleus. He considers it doubtful 
whether they are to be regarded as true Infusoria, or as developmental 
stages of endoparasitic worms. They are said to reproduce almost 
always by transverse division. O.ranarum is said to be most diver- 
gent from other ciliate Infusoria since it has no nucleus or con- 
tractile vacuole and has never been seen in division. 
Lrypie (1857) doubts the position of the Opalinas as Infusoria 
arguing from the many nuclei of the multinucleated forms and from 
the “beautifully cellular structure” of the outer plasma of O. intesti- 
nalis that they may be multicellular forms. 
PaGENSTECHER (1857) regards Opalina as probably a stage in 
the development of a Trematode. He figures a form which seems 
to be O. ranarum. 
Ktune (1859, p. 823) stimulated Opalina (species not mentioned) 
and other Ciliata with strong induction electric currents and saw 
