8 The Microscope. 



The only Chsetonotus in which any structure has been seen that 

 may have the function of a testis is Ch. larus, Ehr. In it a glandu- 

 lar organ beneath the posterior part of the intestine (Plate I, fig. 11> 

 c) has been said by Ludwig to be the male organ, and he states also 

 that Chsetonotus is hermaphroditic, but this Biitschli denies. 



Nervous, muscular and vv^ater- vascular systems exist, but they 

 are generally obscure. The two former were first observed by 

 Biitschli in Ch. maximus, Ehr., but for the discovery of the latter 

 Gosse deserves the credit, as he saw the ciliated tubules in Ch. larus, 

 Ehr., and in his own Ch. Slackice and Ch. gracilis, more than twenty 

 years ago. 



The nervous system consists of two longitudinal, somewhat 

 twisted and convoluted bands, extending, one on each side of the 

 oesophagus and parallel with it, from the oral aperture to near the 

 posterior region of the passage. They are shown as they appear in 

 Ch. maximus, in Plate I, fig. 1, n. 



The water-vascular system is in appearance not unlike that of 

 the Rotifera, so far as the tubules are concerned. The contractile 

 vesicle of the Rotifers and the ciliated funnels are absent, but the 

 long, narrow, often much convoluted tubes are ciliated within aa 

 they are in the Rotifera. In Ch. maximns, Ehr., Biitschli represents 

 them as consisting of two clusters of tubules, one on each side of the 

 intestine anteriorly, and taking a curved direction posteriorly across 

 that passage. I have observed them in Ch. rhomboides, where they 

 are much more simple in character. In Plate I, fig. 1, tv points out 

 the tubules in Ch. maxiynus, Ehr. 



Occasionally one or more very narrow bands are visible near 

 the lateral margins of the body and parallel with them, as shown in 

 Plate I, fig. 1, X. These are supposed to be muscular fibres, and, so 

 far as I know, have been seen by Biitschli only. The other muscular 

 elements are more numerous. They consist of more or less scattered, 

 radiating, contractile bodies, which are sometimes nucleated, as 

 shown in Plate I, fig. 1, m. 



EXPLANATION OF THE FIGURES. 



PLATE I. 



Figure 1. Ch. maxiimts, Ehr. ; fi'om an unusually short and 

 stout individual, in which the internal organs were very distinct; rn, 

 radiating contractile cells; x, probably longitudinal muscle-fibres; 

 w, water- vasciilar system; ov, ovary; a, anal aperture; n, nervous 

 system- (After Biitschli.) 



