262 BALANTIDIUM COLI. 



ranee, and the large cilia sink deeper into it, but finally persist in their 

 former size only on the left margin. Sometimes one finds animals 

 which are all but separate, being united only by a thin connecting 

 thread. In one case in which I observed the separation, I saw this 

 thread draw itself together into a ball, which remained connected 

 with the anterior individual, and looked just like a little ball of dung 

 which the animal was about to drop. These adherent balls are often 

 seen in Balantidium, and have been quite generally described by 

 previous investigators as dung-balls. That this is a mistake I have 

 little doubt, not only because of the previous observation, but because 

 of the fact that it is always the smaller and more slender forms with 

 narrowed posterior extremity that bear this appendage. The size of 

 this ball varies greatly, and is in some cases so considerable that 

 Ekeckrantz regarded it as a bud, and was thereby led to the con- 

 clusion that these Infusorians also reproduced by budding. Although 

 I have actually observed a small vacuole inside one of these balls, 

 I am far from being inclined to interpret this occurrence according 

 to Ekeckrantz's theory. The fact that budding occurs in but few 

 groups of Infusoria, and has never yet been observed in forms aUied 

 to Balantidium, is of some weight in this connection. The same 

 may be said in regard to the statement that it is the posterior end of 

 the body M'hich buds, for a terminal budding is, as far as we know, in 

 the highest degree improbable among the Infusoria. 



Division occurs, to all appearance, so frequently and rapidly 

 among the Infusoria, that we can easily conceive how the number of 

 parasitic inmates, after a time, considerably increases, and after a 

 lengthened period becomes quite immeasurable. The parasitism itself 

 cannot, of course, be thus explained. 



The Mode of Infection by this parasite is at present in a state of 

 uncertainty, and a decided proof is needed as to the form in which 

 the Balantidium gains admission to its host, and until this is furnished 

 our knowledge of the subject cannot claim to be satisfactory. 



So far as we can judge from the analogy of other intestinal In- 

 fusoria, and especially from the facts lately established by Engelmann^ 

 and Zeller^ as to Opalina, we may on a priori grounds expect that this 

 transmission occurs in the encapsuled state, and therefore under cir- 

 cumstances which allow to the Infusorians a further distribution out- 

 side the living organism. And, as a matter of fact, it has been proved 

 beyond a doubt that Balantidium has such an encapsuled state. Even 

 in the first edition of this work I was able to state the results of some 

 observations of this point, which were afterwards confirmed by Stein.'' 



^ Morphol. Jahrb., Bd. i., p. 673, 1876. ' Zeiischr. f. wiss. Zool., Bd. xxix. , p. 352, 1877. 



= Against this <'°"°''°5^^/fey*]^V()9?c5?3;^^^ Wising'a observations have not 



much weight. Besides, Wisrag does not raspute the correctness of our statements, but 



