CASH ON THE ROTIFERA. 131 



Professor Williamson says that the young Melicerta commences its 

 house by secreting a " thin hyaline cylinder," and the first row of pellets 

 is deposited, not at the base, as would be expected, but in a ring about 

 the middle of the tube. " At first new additions are made to both ex- 

 tremities of the enlarging ring : but the jerking constrictions of the animal 

 at length force the caudal end of the cylinder down upon the leaf, to which 

 it becomes securely cemented by the same viscous secretion that causes the 

 little si3heres (pellets) to cohere." Once I came upon a Melicerta which 

 had not commenced to build at all. It had not laid a single brick, and 

 such an odd appearance did it present, with its two arms, or *' tactile 

 appendages," stretched out at almost right angles to its body, that I was 

 greatly puzzled at first to make out what it was. It became clear, however, 

 on a close examination, that it was nothing but a young Melicerta. It did 

 not commence building whilst under my observation. 



The great beauty of the Melicerta lies in its ciliary apparatus. To 

 one unaccustomed to the use of the microscope there is nothing more en- 

 chanting than this. Everything else is for the moment lost to view. The ob- 

 server sees the ciliary waves chasing one another in regular succession round 

 the lobes of the disc, and can hardly persuade himself that there is not an ac- 

 tual rotatory movement going on. It is, however, the result of an optical illu- 

 sion " produced (as Mr. Gosse says,) by the cilia being brought momentarily 

 closer together at certain regular points, causing opacity, and alternating 

 with correspondent separations, causing transparency. These waves run 

 ceaselessly round, but the cilia themselves do not change their places, they 

 merely bend and straighten themselves in rhythmic alternation." This 

 action may be more distinctly perceived, and the building operations more 

 clearly traced, by the introduction of a little carmine into the water. 



As is the case with Stephanoceros, the male of the Melicerta is un- 

 known. The creature is supposed to be dioecious, and the fact that, 

 among the vast number of specimens that have been examined, no trace 

 of a male organisation has been found, seems to afford some ground for 

 this supposition. 



My next communication will be on the Floscules. 



