366 ENTOZOA. 



however, is admitted to disappear as age advances. " In Oxyuris 

 amhigua and vlscans oxyurus," says Eberth, "in the ventral line, 

 there lies above the vaginal opening a roundish or oval sac, bounded 

 by a delicate wall^ which onens through a short narrow passage to 

 the outside by a fine opening. Towards the upper and lower end 

 of the sac the ventral line becomes broader, so that one may say 

 the sac lies in a special widening of the ventral line. In this I re- 

 cognise the simplest form of the glands, which in many nematodes 

 open at the ventral surface." If Eberth's description be correct, 

 this so-called sucker may be regarded as a special gland orifice. 



Respecting the water- vascular system itself, it may be remarked 

 that we have here four well-marked longitudinal vessels, one dorsal, 

 one ventral, and two lateral, occupying their usual situation. 

 According to the age of the Oxyuris they seem to present very 

 difierent appearances ; at least, this must be the case, if they are to 

 be regarded as identical with Walter's so-called fat-canals. In the 

 adult Oxyuris ornata, this observer finds the dorso-ventral canals 

 narrower than the lateral ones, these side vessels giving off nume- 

 rous delicate branches. On this point, however, the views of 

 Eberth are somewhat at variance with those of Walter. Speaking 

 of Oxyuris amhigua and Ascaris oxyura, Eberth remarks that he 

 finds " two comparatively stout, sometimes slightly curved lateral 

 vessels, each consisting of a stouter tube, including a small 

 delicate-walled vessel, the space between the two being filled up 

 with a finely granular mass. The central canal is bounded on 

 either side by a single row of small nuclei. The dorso-ventral 

 vessels are small canals filled with fine granules." Walter speaks 

 of anastomoses between certain of these longitudinal vessels, but 

 in Eberth's experience they do not exist. Many other points of 

 dispute might be brought forward concerning the water-system, 

 but one's patience gets exhausted when one finds no two observers 

 exactly agreed. 



Again, as regards the nervous system, it is difficult to speak 

 with positiveness, notwithstanding the asseverations of Schneider, 



