INTRODUCTION. 29' 



which several Closteria adhered elegantly by one extremity ; 

 in about a quarter or half an hour many of them were situated 

 in the same manner upon a higher part of the leaf: not a 

 single animalcule was found on the side of the leaf, nor ad- 

 herent longitudinally to it. They had evidently moved 

 during the above time from the lower to the upper part of 

 the leaf. If we observe their motions under the microscope 

 they are not so rapid as those of many other polygastric in- 

 fusoria, but the motion is always evidently animal. They 

 swim, especially in summer, in the most varied directions, 

 and I have frequently seen CI. acerosum and Lunula swim 

 against the current when the water on the object-holder was 

 flowing towards one side, whilst fragments of plants, various 

 kinds of Spirogyra and Oscillatoria were carried away. It is 

 difficult here to discover anything but animal motion ; to 

 explain this however by electricity, as Turpin attempted, is 

 unnatural, and not less absurd than that of the muscular 

 fibre by the same natural agent by Strauss. But the rela- 

 tions of the organization of the Closterina are likewise in 

 favour of their animal nature. In illustration of this I 

 shall confine myself to CI. acerosum. We see that the animal, 

 which is expanded in the middle, is elongated symmetrically 

 on each side. In the middle there is a transverse fissure, 

 which probably serves for the admission of nourishment ; 

 since, when this animal is kept for some time in coloured 

 water, we perceive little accumulations of the colouring 

 matters. At the extremities we see on each side a vesicle, 

 in which minute granules (?) incessantly move. In other 

 species there is moreover a small aperture ; it is situated 

 more posteriorly, and is perhaps connected with the cell. 

 Ehrenberg twice saw in this animalcule filaments (feet ?) pro- 

 ject from it. Internally there are on each side two or four 

 cords, and a row (in other kinds several) of granular bodies. 

 In the species figured, I have so often seen the above change 

 in relative position, that I have been compelled to wait until 

 they again appeared in their original position in order to 

 delineate them. All this is not plant-like ; and if the carapace 



