Opalina. 309 
Licer & Dusoscg (1904 a) separate the family Opalinae, inclu- 
ding the genera Opalina, Opalinopsis, and Foettingeria, from the <Ano- 
plophryinae including the genera <Anoplophrya and Hoplitophrya; a 
classification which seems reasonable. Instead, however, of believing 
with Ltarr & Deusoscg that the resemblance between these two 
families is a superficial one due to convergence caused by parasitism, 
I think that the two families show real, though not close relationship, 
the <Anoplophryinae being the nearest relatives of the Opalinidae, 
unless Scnusorz’ new Pycnothrix monocystoides stands still nearer. 
The difference between the two groups, is, however, probably too 
great to allow them with propriety to be placed in the same family, 
Opalinidae, as is usual. The absence of a distinct macronucleus in 
the Opalininae is the chief distinction between this family and other 
Ciliata; but, as I have shown, the distinction is not a fundamental 
one, the macronuclear elements being present in the nuclei of Opalina. 
Abnormalities. 
Some very interesting abnormal phenomena have been observed 
in the course of the work described in the previous pages. Brief 
reference should be made to some of these. 
Under unfavorable conditions the animals enter on changes which 
in some respects resemble the phenomena preceeding or accompany- 
ing sexual reproduction. We have already noted that rearing Opa- 
linae outside the host tends to make them divide. Even in the fall, 
when division is very infrequent in freshly taken material, it is 
found quite readily among animals that have been kept from one 
to three days in cultures. This recalls the fact that in the spring, 
when the period of sexual reproduction is approaching, division be- 
comes much more rapid. 
The major part of the chromatin in the nuclei of animals kept 
long in cultures tends to aggregate into compact masses (Pl. XXI, 
Fig. 94, lower nucleus of Fig. 95). This drawing together of the 
chromatin may go so far as to form a single ball. These pheno- 
mena. recall the gathering of the vegetative chromatin into two 
masses before encystment, previous to their extrusion into the cyto- 
plasm. R. Herrwie (1898) has shown that in starved individuals 
of Actinosphaerium the chromatin condenses into a single mass, while 
21* 
