292 Dr. V. Sterki on a new Infusorian. 



The ciliation is of remarkably peculiar character. The 

 anterior part of the body, from one third to nearly the half, 

 bears scattered, short, fine cilia, like those of the Stentorina?, 

 but not so close together, while the hinder part and the peduncle 

 remain perfectly naked. These cilia are usually directed 

 rather forward ; their movements, at least according to my 

 observations, are slow and not very effective, and certainly 

 incapable of taking any essential part in the locomotion of the 

 animal. According to Claparede and Lachmann the species 

 of Tintinnus living in the sea have the body entirely ciliated ; 

 while T. fiuviatilis, which I only observed closely after T. 

 semiciliatus, is entirely destitute of the fine body-cilia. The 

 species now under consideration consequently holds a middle 

 place in this respect. 



It was particularly interesting to me to be able to ascertain 

 exactly, in T. semiciliatus, the position and form of the so- 

 called adoral cilia. Here these are not simple seta? or styles, 

 any more than in the Oxytrichinre *, Euplotina?, Stentorina3, 

 &c, but flat membranes with a long insertion. There are 

 about 15-20 of them, which, however, do not stand trans- 

 versely, i. e. perpendicular to the series, as in the above-men- 

 tioned groups, but obliquely, thus forming, in this respect, 

 a very interesting intermediate step between the " Hetero- 

 tricha," such as S tenter, and the " Peritricha," although most 

 nearly related to the former. 



It has been elsewhere f stated that the adoral membranellse 

 of the Oxytrichinae &c. originate as small lists, rising one 

 after the other, which gradually, by continued growth, attain 

 their normal size and form. In the Vorticellinfe, on the con- 

 trary, according to my observations, a single, closed, annular 

 (i. e. spiral) border rises, and in its further growth becomes a 

 single membrane. It is only when this has attained a con- 

 siderable breadth (representing about half the length of the 

 future cilia) that it begins to become fibrous at its free margin, 

 so that, while growth still continues in the direction of length, 

 a splitting at the same time extends more and more backward. 

 In the species of Tintinnus, therefore, we have, to a certain 

 extent, a middle form ; the series is from the first broken up 

 into pieces, which, however, are not placed at right angles, 

 but obliquely to the series. Or might the course of develop- 

 ment have followed the opposite direction ? 



From its insertion each membrane widens outwards, at first 

 slowly, then more rapidly. From about the middle it is cleft, 



* Zeitschr. fur wiss. Zool. Bd. xxxi. pp. 44 et seg. 

 t Zeitschr. fur wiss. Zool. Bd. xxxi. p. 46. 



