604 DE. H. CHAELTON BASTIAN ON THE ANATOMY AND PHTSIOLOGT 



effected in part by means of the fluid so constantly observed in the alimentary canal of 

 these animals, which is kept in almost perpetual movement by the rapid undulations of 

 their bodies. As first observed by Carter in his Urolabes palustris*, and since wit- 

 nessed by myself in Dorylaimus stagnalis, there seems to be a more special provision for 

 a respiratory process of this nature amongst the Dorylaimi, somewhat similar to what 

 occurs amongst the Naldinoe. The posterior portion of the intestine presents a modified 

 structure in these species, which in all probability has something to do with the process 

 alluded to ; in Dorylaimus stagnalis, for instance, for a distance of -^" of an inch it is 

 almost devoid of the thick lining of hepatic cells met with throughout the rest of its 

 extent (Plate XXVIII. fig. 4, a). In individuals of this species I have seen sudden jets 

 of clear fluid expelled, by contraction of the intestine, through the anal cleft, in a peri- 

 odical manner, at intervals of four or five minutes. After its expulsion the anal cleft 

 seems to close immediately with valve-like rapidity, and how the fluid enters for the 

 next discharge is rather obscure. In the Naidince the process is perfectly simple ; the 

 fluid is introduced through the anal aperture by the agency of powerful cilia lining the 

 whole posterior portion of the intestine, and is as distinctly expelled by intestinal con- 

 traction. The most careful search, however, has revealed no trace of the presence of 

 cilia in the Dorylaimi. It is true, they may be so small as to have escaped recognition. 

 In the genera Tylenchus, Flectus, Aphelenchus, and Cephalohus, the ventral gland is in 

 a somewhat rudimentary condition, and the integumental pores seem wanting altogether ; 

 it therefore seems possible that the superadded lateral vessels met with in these animals 

 may in some way be connected vsdth the function of respiration f. 



ORGANS OF GENERATION. 



I have comparatively little to say on this subject. There is no particular discrepancy 

 in the accounts given of these structures by different observers; their general form and 

 arrangement is pretty well known, and nothing more was likely to be learned from them 

 which would be of material assistance in determining the affinities of the Nematoids. I 

 have therefore not made these organs the subject of any systematic investigation, and 

 in addition to pointing out their prevailing form in the free Nematoids, have only a few 

 scattered facts to mention under this head. 



In the " Monograph on the Anguillulidse," I called particular attention to the fact of 

 the great uniformity in the disposition of these organs amongst the free Nematoids, and 

 stated that for this amongst other reasons it seemed to me desirable to locate them in a 

 family altogether distinct from those into which the parasitic species are divided, since 

 in only two or three exceptional parasitic species is the same arrangement met with. 



The form and position of these organslf;, in both the male and female Dorylaimus stag- 

 nalis, I have represented in Plate XXVIII. figs. 1 & 2, and this may be considered as 



* Really Boryhimus paltistris. Tide Ann. of Nat. Hist. Ser. 3, vol. iv. p. 33, pi. 2, fig. 7. 



t Vide note, p. 619. 



t For the sake of clearness they have been drawn in a somewhat diagrammatic manner. 



