130 THE NATURALIST. 



Without entering into tlie question of the propriety of this change, — 

 which, however, it may not be amiss to say is in some respects an ad- 

 mirable one — I propose to supply a few notes with regard to Melicerta 

 ringens. The operation of brick making, which is its peculiar characteristic, 

 is as interesting a one as can well be conceived. Let us imagine that we 

 have a young and vigorous specimen before us. The first thing that 

 attracts our attention is, of course, the machinery of the expanded disc. 

 We cannot avoid noticing it, and so beautiful is the spectacle that if we 

 have never seen a Melicerta before, some time will elapse before we can be 

 persuaded to take our eyes from it ; but if we look carefully we shall see a 

 little below this — if the creature happens to be engaged in building — a 

 small circular or cup-like cavity, within which a little pellet is revolving 

 with a ceaseless and rapid motion. This pellet is identical in shape and 

 size with those which form the case. Now let us watch the movements of 

 the creature rather closely. We see it sway violently from side to side — 

 its flower-like disc the while being considerably changed in outline — the 

 edges of each lobe or petal are turned upwards and made to approach 

 each other — presently it bends forward and deposits the pellet, or brick, 

 or whatever we choose to term it, with the utmost precision, always taking 

 care to deposit each one so as to make its house gradually wider as it in- 

 creases in height. When the Melicerta has " righted" itself, it re- 

 commences its brick-moulding ; in a few minutes the little circular cavity is 

 re-filled, and another pellet is laid. Sometimes, however, though very 

 rarely, the Melicerta does not succeed in depositing the pellet in its proper 

 place. On one or two occasions I have seen it fail, when it has been 

 driven away by the ciliary current. The pellets, which are apparently 

 spherical, are cemented together by a glutinous substance secreted by the 

 Melicerta in the cavity in which they are moulded : this substance is also 

 mixed with the fine particles from the surrounding water, of which they 

 are composed, in order to give them cohesion, else they would readily be 

 dissolved.* As it is they preserve their consistency for a considerable 

 length of time. Usually, however, in a few days after the death of the 

 animal they disappear. During the present summer I introduced a large 

 number of MelicertsD into my aquarium on the leaf-stems of Anacharis, 

 but from some cause or other, which I am unable to explain, they all 

 died, and their cases soon became dissolved. 



* In the last edition of " Pritcbard's Infusoria," these pellets are erroneously said 

 to be secreted. 



