OF THE ROTATORIA. 425 



by Dobie in the pseudopodiiim of Floscularia ; and Leydig mentions a clear 

 gland or space at the root of the tail of Lacinidaria, from which he supposes 

 a duct to extend to the extremity ; such a structure Huxley cannot discover, 

 but states that the extremity of the tail always seemed to him " to present 

 a ciliated hemispherical cavity, closed above ;" the supposed gland at the base 

 he called a " vascular mass." 



An active secreting power is displayed by those Rotatoria which invest 

 themselves in cases or urceoli ; for such cases are always produced fi'om the 

 animal, and are the result of excretion. The formation of its case by the Meli- 

 certa ringens has often been most thoroughly examined ; and Mr. Gosse was 

 enabled to watch the deposition of pellet by pellet of the excreted matter. 

 This direct observation has entirely overthrown the prevalent notion first ad- 

 vanced by Ehrenberg, that the case was built up of excrementitious particles 

 discharged from the alimentary canal. The organ actively engaged in the 

 building of the case is seated immediately above the long tubular process 

 extending from the neck of the animal (XXXYI. 1 c) ; it is cup-shaped, 

 and its concave sirrface so ciliated, that when in full activity it seems 

 to revolve. In this, which Mr. Gosse calls the ^^ pellet-cup, ^^ the building- 

 material seems to be prepared and fashioned into an oval or hexagonal figure, 

 and then the pellets so moulded are regularly laid down in rows, " straight 

 and uninterrupted perpendicularly," but zigzag transversely, so that a dia- 

 gonal disposition is the result. " Each peUet, examined separately, is of a 

 yellowish or olive colour, composed of granules ; the whole tube is of a red- 

 dish-brown (XXXYI. 1 d). After a certain number were deposited in one 

 part, the animal would suddenly turn itself round in its case, and deposit 

 some in another part." It seems that the action of the pellet-cup is volun- 

 tary, and not always coexistent with the passing of the ciliary current over 

 the chin. The animal frequently makes abortive efforts to deposit a pellet, 

 and sometimes bends forcibly forward to the edge of the case before the pellet 

 is half formed. Coloiu-ed particles in the water are hurled round the margin 

 of the ciliated disk until they pass off in front through the great sinus be- 

 tween the large petals ; and the atoms, if few, glide along the facial surface, 

 following the irregularities of the outline with great precision, and, dashing 

 round the projecting chin, lodge themselves one after another in the little 

 cup-like receptacle beneath, in which they are whorled round with great 

 rapidity, and prepared into pellets for the construction of the case. On mix- 

 ing carmine with the water, the torrent that poured off in front and the ap- 

 pearance of a rich crimson pellet in the cup were instantaneous. A large 

 animal which had its case accidentally slit for some distance, watched for 

 several days, was seen to make pellets frequently ; yet it never deposited them 

 nor attempted to construct a new case, but let the pellets float away." 



Such is a resume of Mr. Gosse's interesting observations. Prof. Williamson 

 adds that, when the animal is not engaged in its architectural occupations, 

 the sac (pellet- cup) becomes so contracted as to be almost invisible. 



In connection with this subject of secretion, must be mentioned the views 

 of Leydig respecting the accumulation of granules or crystalline particles 

 seen in many embryonic and young Rotatoria, enclosed in a sac contiguous 

 to the cloaca (XXXYII. 4; XXXYIII. 7, 8). Ehrenberg remarked these 

 granular heaps in Microcodon, Lacinularia, StepJianoceros, Floscularia ornata, 

 Enteroplea, and in Notommata granulans, and called them at one time " a 

 dark glandular body or speck," at another " a single glandular organ " having 

 no evident function. Weisse represented them to be unconsumed and 

 stiU-remaining yelk- substance, and supposed the animals presenting such 

 granular masses '^ premature " or " aborted." Williamson noticed similar 



