OXYUEIS VERMICULARIS. 365 



perhaps especially in the formation of its generative organs. 

 Walter was unable to detect any efferent duct to these four 

 canals. As far as I can glance over the whole arrangement, it 

 must be the principal object of further investigations to ascer- 

 tain whether a union of each pair of these canals in the apex of 

 the tail to form a common canal does not take place. Thus 

 Walter observed from the apex of the tail to the sucking disc 

 placed in the upper part of the body, in the middle of the 

 ventral surface, two canals, which are extraordinarily delicate 

 towards the apex of the tail, running in innumerable convolutions 

 around the intestine and laterally from it, becoming stronger to- 

 wards the orifice of the sucker, having exactly the same contents 

 as the fat-canals, and also, like these, losing themselves in the 

 corium of the apex of the tail. Consequently, no information 

 can be given at present as to whether these six canals are actu- 

 ally produced as six, or whether there are only four canals 

 with two efferent ducts. We only know that these canals all 

 bear the same contents during the youth of the animal, and that 

 they also retrogress simultaneously, so that they probably have 

 one other same function. Whether these organs are produced 

 in the same way iu the young state of Oxyuris vermicularis as in 

 O. ornata, whether a perforated ventral sucker exists here, 1 and 

 becomes retrograded at a subsequent period of existence into a 

 cleft which is easily overlooked ; and whether these are not con- 

 ditions which occur in all nematode worms, are points on which 

 we are still in the dark. It appears to be very probable, how- 

 ever, that such circumstances occur in very many, if not all, 

 nematode worms. Thus Bagge found a fine transverse cleft in 

 the median line of the belly in Ascaris acuminatus ; others have 

 found a similar organ in Strongylus hypostomus and a ventral 

 sucker in Ascaris brevicaudatus. Dujardin and Von Siebold met 

 with two canals opening in the median line of the belly in 

 Ascaris dactyluris and paucipara, and it is probable that these 

 authors had old worms before them, in which these organs had 

 already become retrograde. 



1 Walter is of opinion that such a ventral sucker is, perhaps, necessary to the 

 nematode worms during the early part of their existence, in order that they may adhere 

 by sucking with it to the walls of their habitation during the period of their metamor- 

 phosis, and thus pass through this stage in greater cmietness. The sucker would then 

 resemble other caducous organs occurring during the larval condition of animals ; but 

 such individuals would then be, as it were, larvae of nematode worms. 



