the Ciliate Infusoria. By G. J. Allman. 175 
be found among tbe zoophytes, and their proper systematic seat 
would be in the primary group of the Ccelenterata. 
Though few zoologists will now be prepared to accept the con- 
clusions of the Genevan naturalist and his associate, the ccelenterate 
relations of the Infusoria has recently found an advocate in Greeff.* 
In an elaborate memoir on the Yorticellae, Greeff sees in the very 
well-marked distinction between the external or cortical layer and 
the internal soft body-substance, a proof of the views maintained 
by Claparede and Lachmann ; and he considers this position still 
further confirmed by the presence in Epistylis flavicans of nume- 
rous oval or piriform, brilliant, well-defined capsules, which are 
generally distributed in pairs below the outer layer, and which, 
under the influence of a stimulus, emit a long filament, thus closely 
resembling the thread-cells so well known as characteristic elements 
in certain tissues of the Ccelenterata. 
It must be here remarked that the presence of similar bodies in 
the Infusoria, where they have been described under the name of 
trichocysts, has long been known. Though varying in form, they 
all possess a more or less close resemblance to the thread-cells of 
the Coelenterata. Their presence undoubtedly indicates a step 
upwards in the differentiation of the organism, but, as we shall 
presently see, it offers no valid argument against its unicellularity. 
In his admirable ‘ Principles of Comparative Anatomy,’ f 
Gegenbaur expresses doubts as to the sexual nature of the repro- 
ductive phenomena of the Infusoria, and is disposed to regard the 
so-called embryo-sphere, to which the nucleus gives rise, in the 
light of a proliferous stolon, from which several zooids are in some 
cases thrown off. Arguing from the Acineta-like form of the 
young in the higher Infusoria, as shown by Stein, and comparing the 
transitory condition of this with the permanent condition of the true 
Acinetae, he believes that we are justified in regarding the Acinetae 
as the ancestral form from which the proper Infusoria have been 
derived. He further compares the contractile vesicle and its canals 
in the Infusoria with the water vascular system of the worms, and 
believes that a parentage with these higher forms is thus indicated. 
Gegenbaur, moreover, expresses himself strongly against the uni- 
cellular theory. He regards, however, the absence of distinct cell 
nuclei in the substance of the Infusoria as affording evidence of 
their composition out of several “ Cytodes ” or non-nucleated proto- 
plasm masses rather than out of true nucleated cells. 
Still more recently, Biitschli has given us the results of obser- 
vations on the conjugation of Paramoecium aurelia.% He is led, 
* Greeff, “ Untersuckungen iiber den Ban und die Naturgeschickte der 
Yorticellen,” £ Arckiv fur Naturg.,’ 1870. 
t ‘Grundsiige der Vergleickenden Anatomie,’ 1870. 
% O. Biitsckli, “Einiges iiber Infusorien,” ‘ Arckiv f. Microscop. Anat.,’ 1873. 
