59 



and by the closeness of their investiture, they may be considered as 

 clothing. 



The subject of the present paper is of this class of animal arti- 

 ficers. It is an animalcule, so minute as to be with difficulty appre- 

 ciable by the naked eye, inhabiting a tube composed of pellets, which 

 it forms and lays one by one. It is a mason, who not only builds 

 up his mansion, brick by brick, but makes his bricks as he goes on, 

 from substances which he collects around him, shaping them in a 

 mould which he carries upon his body. 



Neither the animal itself nor its architectural habit is any new 

 discovery ; both the one and the other were made known at a very 

 early period in microscopical science. The illustrious Leeuwenhoek 

 discovered the species at Delft, in 1703, and described its appearance 

 and manners in the Phil. Trans, (v. 176, abridged edition). It was 

 afterwards noticed by many observers ; until, at length, in the mag- 

 nificent work of Prof. Ehrenberg, its past history was detailed, and 

 enriched by the addition of his own most admirable observations. 



As, however, my own observations on this animal were made be- 

 fore I had seen those of either of these illustrious microscopists, and 

 as, in the most interesting part of its economy, they disagree with the 

 conclusions of the latter, and add something to those of the former, 

 I shall commence with a brief description from my own notes. 



Attached to the roots of Lemna, or the narrow leaves of Char a, Ni- 

 tella, Ceratophyllum, and other sub-aquatic plants, may often be ob- 

 served a tube, a little wider at the top than at the bottom (Plate XII., 

 fig. 4). It stands erect, being fixed by the base, which is sometimes 

 dilated ; the mouth being uppermost. This tube is of a dark yellow- 

 ish or reddish brown hue, and is found to be composed of a multi- 

 tude of round pellets, set very regularly in a sort of mosaic, apparently 

 agglutinated by a cement insoluble in water. The upper part or rim, 

 is usually irregular, as if broken off with a ragged edge (fig. 2, a). 



But while we gaze, a curious object is slowly protruding from this 

 tube. A complicated mass of transparent flesh appears, involved in 

 many folds, displaying at one side a pair of hooked spines (fig. 2, b), 

 and at the other, two slender truncate processes, projecting horizon- 

 tally (fig. 2, e). As it exposes itself more and more, suddenly two 

 large rounded disks are expanded, around which, at the same instant, 

 a wreath of cilia is seen performing its surprising motions (fig. 4, 

 d). Often the animal contents itself with this degree of exposure, 

 but sometimes it protrudes farther, and displays two other smaller 

 leaflets opposite to the former, but in the same plane, margined with 



