220 Miscellaneous. 



Coming now to the new Infusorian proposed as an intermediate 

 foftn, we shall see that M. de Mereschkowsky is equally ill-informed 

 with respect to it. This type, in fact, is much better known, and 

 has been so for a longer time, than he thinks. It was first dis- 

 covered in the North Sea, and published by Claparede and Lachinann* 

 under the name of Hcttteria index. Since then it has been met with t 

 first in the marine aquarium of Frankfort by Freseniusf , who gave 

 it the name of Hatteria tenuicollis ; a second time in the marine 

 aquarium of Ereslau by (John J, who baptized it by a third name 

 Acarella siro ; and, finally, for the third time by Quennerstedt§, upon 

 the coast of Sweden. All these different names belong to a single 

 species more or less imperfectly seen or studied. For my own part 

 I have met with it on the coast of Brittany, at the Zoological Labo- 

 ratory of RoscofF, and very frequently upon the Algerian coast. 

 Stein |J S without having personally observed it, classes it, T think 

 definitively, in his genus Mesodiniam. We see therefore that it is a 

 widely distributed type, and has been already much studied by good ob- 

 servers. All these authors, without a single exception, have regarded 

 Mesodinium pulex as a Ciliated Infusorian nearly related to the 

 Hatterice. 



The whole of the* new theory of M. de Mereschkowsky is founded 

 on the presence of small appendages arranged upon the margin of 

 the orifice of the neck, and which he thinks he has been the first to 

 perceive. But they are already very well figured in the drawings 

 of Claparede and Lachmann, as well as in those of Fresenius, who, 

 moreover, has described them in his text. I have myself observed 

 them many times. The Russian naturalist makes them out to be 

 suckers identical with those of the Acinetina ; but I must declare 

 that I have seen nothing in them to make me regard them as such, 

 any more than Claparede, Lachmann, and Fresenius ; and it must 

 be admitted that M. de Mereschkowsky has got no further than we 

 have in this respect. Their assimilation to the suckers of the Acinetina 

 is a purely gratuitous assumption on his part, and not founded upon 

 any positive observations. To assert a fact of such importance, and 

 draw from it such important conclusions, he ought to have positively 

 seen these appendages acting as true suckers : this we are not told ; 

 and it has evidently not been seen. 



I think, moreover, that it was useless to go so far to seek the 

 explanation of the function and significance of these appendages. 

 All observers, including M. de Mereschkowsky himself, have re- 

 marked that Mesodinium pidex often attached itself to objects by its 

 anterior extremity, and remained thus for a long time motionless. 

 Hence, I am convinced that these appendages have no other function 

 than that of serving as organs of fixation ; and the Russian naturalist 

 assures us that he has seen them act as such. 



Another consideration, drawn from comparative morphology, may 



* Etudes sur les Infusoires et les lilrizopodes, p. 370, pi. xiii. figs. 10, 

 11 (1858-60). 



t Der ZoologLsche Garten, 1865, p. 84, figs. 11-13. 



\ Zeitschr. f. wiss. Zool. xvi. p. 293, figs. 32, 34 (1866). 



§ Bidrag till Sveriges Infiisorie-fanna, iii. p. 32 (18G9). 



|| Der Organismus &c. ii. p. 162, note 2 (1867). 



