22 Gmrginu Sweet: 



that of other forms (with the same exception), being often twice the* 

 thickness in those forms. The oesophageal bulb or " cardia " also- 

 is unusually conspicuous, occupying on an average the terminal 

 .064 mm. of the oesophagus. In specimens of 0. gibsoni examined 

 by me, it was not seen, though from Leiper's and Breinl's descrip- 

 tions of the occasional thickness of the posterior end of the oesopha- 

 gus, something of the sort was evidently present in some of their 

 specimens, this probably accounting for this exception in regard to 

 the thickness of the oesophagus mentioned above. A glance at the 

 averages of length and diameter of the oesophagus of 0. indica and 

 0. gibsoni will show the extent to which that in the former exceeds 

 that in the latter. The Cloacal opening is also often further from 

 the posterior end than in specimens of 0. gibsoni examined by me, 

 though the range in 0. indica corresponds approximately with that 

 given by other workers for 0. gibsoni. The spicules show a certain 

 amount of variation from other forms, most marked, however, in 

 the case of the long spicule. This in general exceeds that of any of 

 the other forms, the range of which it overlaps, except the greatest 

 length of 0. gutturosa, while its lowest^range only slightly overlaps 

 the highest range of 0. gibsoni (Breinl) 1 and of 0. bonis. Further, 

 the average length of the long spicule of 0. indica is considerably 

 greater than the greatest length given by any one for 0. gibsoni ; 

 though the range of thickness of the long spicule in 0. indica is 

 included within the total range found in 0. gibsoni. Not only does 

 the long spicule most nearly approximate that of 0. gutturosa in 

 range of length, but also in the fact that the long spicule of 0. indica 

 sometimes appears bifid as in 0. gutturosa. The range in length 

 and diameter of the short spicule agrees approximately with the 

 total ranges found by others and myself in O. gibsoni, though the 

 average, both of length and diameter of the short spicule, is greater 

 than the average of all forms of 0. gibsoni described. The anal 

 papillae also show considerable variation, as was pointed out by 

 us to occur, though to a less extent in 0. gibsoni. The highest 

 number of papillae described by any observer (with the exception 

 mentioned immediately) for the latter species, was seven pairs — one 

 preanal, three ad- (or par-) anal, one post-anal, one precaudal, and 



1 If the figures yiven by Or. Breinl for his male specimens of Onchocerca gibnoni lie analysed, 

 it will he seen that the three individuals in which the length of the lone spicule overlaps the lower 

 end of the range found in O. indica do not show the concurrent characteristics found in O. indica, 

 except that in one case (No. 19), a length of oesophagus (1.074 mm.) which is unique and extra- 

 ordinary for O. gibsoni, is found in a worm having a length of .210 mm. for the lon^r spicule. Apart 

 from this one worm there does not appear to be any regularity of variation in (>. gibsoni, in the 

 features referred to, as characteristic of O. indica. A study of these tables will emphasize the- 

 extreme and irregular variability of Australian specimens of O. gibsoni. 



