OF THE ROTATORIA. 431 



Syrinx, N. Sieholdii, N. Anglica, N. clavulata, and in JSf. Myrmeleo, the 

 number is greatly augmented, and from 30 to 50 tags may be counted. When 

 thus multiphed, they are for the most j^art appended to a clear canal of Httle 

 width and thickness, rather than to one with thick cellular walls. (The tags 

 are mostly more numerous on one side than on the other.) 



" The posterior extremities of the respiratory canals either open at once 

 into the cloaca, as in Tuhkolaria, or more commonly expand to form the 

 contractile scu?, the respiratory vesicle (XXXVIII. 26 i). 



'^ At the first appearance of the respii^atory vesicle, it is of insignificant size, 

 and clearly a dilated state of the united ends of the two respiratory canals. 

 It is then little or not at all contractile. This condition is illustrated in 

 Lacinnlaria and Steplianoceros. " It generally, however, exists as a consider- 

 able and actively contractile sac opening into the cloaca. Its walls are very 

 thin, and covered with a fine muscular network, discoverable in most species, 

 and imagined by Ehrenberg to be vascular. The openings of the respiratory 

 canals into this sac are readily perceived by a proper adjustment of the focus 

 of the microscope." 



From this organization, Ley dig concludes that a portion of the water sur- 

 roimding the animal enters by endosmosis, or possibly by minute orifices 

 hithei-to unperceived, within the cavity of the body, and there mixes with 

 the nutritive juices, the analogue of the blood of higher beings. The simple 

 act of respiration is consequently limited to the imbibition and the intermix- 

 ture of fresh water with the blood. Further, it would appear that the waste 

 material is discharged through the vibratile processes, which by their ciliated 

 appendages direct the fluid into the respiratory canals, from which it escapes 

 either fii'st into the contractile sac, and thence into the cloaca, or at once into 

 the latter. 



Here the question of a glandular, a renal function performed by the re- 

 spiratory tubes meets us ; but it will be more convenient to defer its consi- 

 deration until we have set forth the researches of iSlr. Huxley, who differs in 

 not a few details from Leydig : — we must premise that they api)ly specially 

 to the Lacinidaria socicdis, to which, among other peculiarities, he assigns the 

 absence of a contractile sac, although Leydig affirms a veiy small one to 

 exist. 



Prof. Huxley acquaints us that the opinion of Oscar Schmidt is, " that the 

 ends of the water- vessels are closed, and that the vibrating body is within 

 them." And he goes on to say — '' There is no contractile sac opening into 

 the cloaca as in other genera ; but two veiy delicate vessels about ^^th of 

 an inch in diameter, clear and colourless, arise by a common origin upon the 

 dorsal side of the intestine. AVhether they open into this, or have a distinct 

 external duct, I cannot say. 



" The vessels separate ; and one runs up on each side of the body towards 

 its oral side. Arrived at the level of the phaiyngeal bulb, each vessel divides 

 into three branches : one passes over the pharynx and in front of the pha- 

 rjTigeal biilb, and unites with its feUow of the opposite side, while the other 

 two pass, one inwards and the other outwards, in the space between the two 

 layers of the trochal disk, and there terminate as caeca. Besides these, there 

 sometimes seemed to be another branch just below the pancreatic sacs. 



"A vibratile body was contained in each of the csecal branches ; and there 

 was one on each side in the transverse connecting branch. Two or more 

 were contained in each lateral main trunk, one opposite the pancreatic sacs, 

 and one lower down, making in aU five on each side. Each of these bodies 

 was a long cilium (y^L-^th of an inch) attached by one extremity to the side 

 of the vessel, and by the other vibrating with a quick undulatory motion in 



