208 Transactions of the 



ticular curves as may severally be induced by the projection of any 

 particular lines in the subject in hand where a repetition of that 

 curve becomes necessary. 



I have selected the dehneation of Melicerta ringens as an 

 appropriate subject for the illustration of this system for several 

 reasons : the First, from the fact of its being such a general 

 favourite in the hands of all observers, it may invest the matter 

 under consideration with an interest that will relieve it of what 

 otherwise would have assumed a prosaic character. Secondly, that, 

 notwithstanding the complete and elaborate descriptions, which have 

 been published on the history of this rotifer, the illustrations accom- 

 panying the same are all, so far as I am able to compare, wanting 

 in that perspicuity necessary to convey an accurate impression of 

 the appearance of the animal in its natural condition. Thirdly, it 

 will afford a variety of points in the projection of its several details 

 that require a very careful application of this system from the 

 diverse positions assumed by the expanded animal and from the 

 varying angles to which it is prone to subject the different append- 

 ages of its head. 



The tube, moreover, is a study in itself; and as the several points 

 in reference to the composition, fabrication, form, and disposition of 

 the pellets during the process of construction require to be under- 

 stood, I beg briefly to recount the most prominent of these points 

 before proceeding to set out the details. 



The preliminary act in the formation of the tube of the young 

 animal is the secretion of a hyaline gelatinous cylinder round about 

 the body, to which the first crudely-formed pellets are attached at 

 some distance above the foot ; these are subsequently forced by 

 sudden contractions of the young animal down upon the support to 

 which the tube becomes permanently fixed, and in some instances 

 these contractions, by reason of the pressure they create, cause a 

 departure from the circular form of the pellets in several of the 

 first laid courses, the outlines of which are rendered hexagonal. I 

 find them, however, more frequently to be indefinitely distorted. 



The operation of buUding is carried on thenceforward to the 

 completion of the tube, but on many occasions it may be noticed 

 that the animal having attained its full development persists in 

 lengthening the tube to an extraordinary extent beyond the limits 

 actually required by the animal in its adult condition. Instances 

 of this I have frequently had under observation, in which the tube 

 has reached a height of fully twice that absolutely required by 

 the fuU-grown animal ; and on such occasions Melicerta manifests 

 that same capacity for inordinately extending the footstalk which 

 obtains with the floscules, remarkably so in F. campanulata, in- 

 stances of which have attained the extraordinary height of ^Vth 

 inch from the foot-attachment to the incurved summit of the dorsal 



