Contrisutions to the Natura History of the InFusoria. 
By Dr. W. ZENKER. 
(Schultze’s ‘ Arch. f. Mikrosk. Anatomie,’ IT, p. 332.) 
(Abstract. ) 
1. On the Pulsating Vesicle-—The pulsating, or, as it is 
more usually though less characteristically termed, contractile 
vesicle, is one of those points in the anatomy of the Infusoria 
which has been the subject of the greatest controversy among 
zoologists. It is one of the most generally existing and 
most remarkable organs of the infusorian body, in most cases 
occurring singly, though in many two or more are found.* 
At a constant point in the body may be noticed a vesicle with 
clear reddish contents, which, with a rhythmical recurrence, 
first gradually enlarges, and then suddenly contracts, so as 
entirely to disappear. The rhythm of these usually very dis- 
tinct pulsations may be rapid or slow. In some Infusoria, 
as, for instance, Actinophrys Hichhornii, it varies so that in 
that species it is frequently very tedious to await the contrac- 
tion of the vesicle. On each occasion the contents of the 
vesicle which have been derived from the tissue of the body 
are expelled from it; and the question arises whether they 
are driven inwardly—that is to say, into the other parts of 
the animal—or outwardly into the surrounding water. In 
the former case it would be, as first asserted by Wiegmann 
in 1835, a circulatory, and in the latter an excretory organ. 
To the advocates of the latter view Ehrenberg especially 
belongs, who was of opinion that the secretion might be 
seminal. This opinion, which was suggested perhaps by the 
enormous power of multiplication of the Infusoria, and was 
taken to be opposed to the doctrine of equivocal generation, 
should be regarded as long since exploded, and especially 
since it has been shown beyond doubt that the reproduction 
of the Infusoria is preceded by conjugation. Such a circum- 
stance would be incomprehensible had impregnation been 
effected so conveniently at every moment, and from the ear- 
liest period of life. In favour of the same view, Oscar Schmidt 
(‘ Froriep n. Notigen,’ 1849) adduced the first confirmatory 
observation in Bursaria leucas of the actual existence of an 
* Amongst examples in which the number of vesicles is most numerous 
may be cited Amphileptus anser, Ehr., in which from ten to fifty pulsating 
vesicles are placed in two longitudinal series, extending from one end of 
the body to the other. The successive pulsations are alternate from before 
backwards. 
