or THE ROTATORI V. 433 



" and the base of the stomach there was one httle tremulous tag, of the same 

 structure as in Notommata aurita. From the same spot also project, into a 

 space of peculiar clearness, two trnmpet-shaped bodies of the greatest delicacy, 

 and without motion." Prof. WiUiamson reminds us, in a note, that he has 

 described two tubes springing from a pyriform organ, apparently hollow, and 

 located immediately below the stomach. Though he saw no pulsation in this 

 organ, it appeared to be the homologue of the contractile yesicle in other species. 

 He belieyes the two filamentous organs to be tubular, and suggests the possi- 

 bihty of their supplying a spermatic secretion, though he is not able to affirm it 

 as a fact. He moreoyer obseryed the \'ibratile spermatozoon-like corpuscles 

 " in yarious parts of the body, where they are apparently enclosed within 

 hollow canals. I have never seen them occupying the two main trunks of 

 the ivater-vascular system, as caeca, nor can I succeed in tracing any con- 

 nexion between them ; " but it is probable that they were really located in 

 some of the branches of that system, as observed by Mr. Huxley in Lacinu- 

 Imia. 



The glandular renal function of the lateral tubes and appendages has the 

 support of analogy among other lowly- organized forms allied to the Rotatoria ; 

 but such an hj-pothesis falls to the ground, if, as Leydig thinks, the urinary 

 concretions noticed and so named by him in embryo and young animals are 

 deposited within the cavity of the intestine, and not in the contractile sac. 

 However, naturalists generally will certainly not accept the doubtful disco- 

 very of the position and the interpretation of the nature of the particles 

 oifered by Leydig as conclusive evidence of the natm^e of those structures, 

 but will, in the absence of direct and exact observation, be rather guided by- 

 analogy. ^Ye will therefore append some extracts, showing the comparative 

 physiology of the supposed respiratory mechanism. 



Leydig writes — " There is the greatest similarity between it and the 

 organs in Lumbricince and HirucUnce, which are conceived to have a respira- 

 tory office. In these are similar contorted and coiled tubes, with a clear 

 canal opening either without an intermediate contractile sac, as in Clepsine, 

 or with one, as in Nephelis. Moreover, the canal opens by a wide ciliated 

 aperture into the cavity of the body ; and in this termination of the tubes I 

 recognize the homologue of the vibratile tags of the Rotatoria. Moreover, 

 the dii-ection of the ciliary motion in the Annelida is inwards to the main 

 canal. In the Lumbricince, Gegenbauer has attributed a renal function to 

 the otherwise-called respiratory canal." 



Dr. Carpenter describes a '' water-vascular system " among all the vermi- 

 form members of the Articulata, and as represented in its simplest type in the 

 Rotifers. " Similar lateral vessels, often ramifying more minutely (especially 

 in the head and anterior part of the body), are found in many of that group of 

 vermifoi-m animals clothed over the whole surface of theii' bodies with cilia, to 

 which the designation TurbeUaria has been given." This writer surmises 

 that the water-vascular system may contain some other fluid than pure water, 

 and, as Van Beneden has suggested, may serve as a urinary apparatus. 



Prof. Huxley presented the followiug philosophical summar}^ of the com- 

 parative relations of the respiratory mechanism of the Rotifer ; before the 

 British Association : — '' In certain Distomata, such as Aspidogaster, there is 

 a system of vessels of essentially similar character with that in Rotifer ; but 

 the principal canals, those lateral trunks which come dii^ectly from the con- 

 tractile vesicle, present regular rh^^hmical contractions. The smaller branches 

 are aU richly ciliated. In other Distomata the lateral trunks appear to be 

 converted into excretory organs, as they are full of minute granules : they 

 remain eminently contractile ; but their connexion with the system of smaller 



2f 



