180 OXYURIS-LARViE HATCHED IN THE HUMAN STOMACH, 



two backwards, along the lateral fields. But the young larvae of 

 Oxyuris vermicular is and o b v e 1 a t a, as I have shown, 

 possess the organ in the form now so well known among free-living 

 Nematodes. By increasing with the growth of the larvfe and 

 becoming bifurcate the simple unicellular form gives rise to tlie 

 larger, later and more complicated system of vessels. 



I have dwelt at some length upon this matter because in the 

 Nematode literature as a whole there lurks a suspicion that the 

 two structures so often mentioned in the preceding paragraphs, the 

 lateral vessels and the lateral fields, are in some way intimately 

 connected with each other, and as a kind of corollary that the 

 lateral fields may be excretory in their function, a suspicion which 

 seems to me groundless. I will add that I have tested the lateral 

 vessels of A s c a r i s 1 u m b r i c o i d e s , the large stomach- 

 worm of man, to ascertain the nature of their contents, and have 

 proved the presence of urea and sodium chloride, weighty evidence 

 in favour of regarding the vessels as excretory organs. Until now 

 the evidence supporting such a belief has been solely morphologi- 

 cal. Schneider failed to find uric acid in the vessels of A s c a r i s 

 mart^inata. I also failed to find uric acid in the vessels of 

 •^ A. 1 u m b r i c o i d e s, but should not deny its presence without 

 first making further tests. I shall give the details concerning my 

 tests and methods at another time, when I can accompany them 

 by the results of further experiments now in progress. 



riiylogenetic. 



In three respects Oxyuris v e r m i c u 1 a r i s seems to difier 

 considerably from the majority of the species of its genus. These 

 are, the peculiar structure of the head, the position of the nerve 

 ring and the position of the j)orus excretorius. In all these 

 respects, the larva stands nearer the average Oxyuris than 

 does the adult, showing that in these particulars vermicular is 

 is a departure from the type of the genus. 



Does the structure of the larva of Oxyuris throw any 

 light on the ancestry of the genus ? A glance at Fig. 2 tempts 

 one to hazard an answer in the affirmative. The striking resem- 



