WORM NODULES IN AUSTRALIAN CATTLE. 325 



surrounding the parasite, especially around the head, is less fibrous 

 than elsewhere, but not invariably so. As in the case of some allied 

 forms it is practically impossible, even with the greatest care and 

 patience, to extract the female worm entire, even after the pre- 

 liminary use of digestive and other like methods. Fifteen and 

 twenty fragments are good records. The length of the worm, 

 found by adding together the lengths of the various pieces obtained 

 by careful dissection, with the production of as few fragments as 

 possible, was in three typical cases of fresh female worms 52.6 cm., 

 90 cm., 140.3 cm. {compare Cleland and Johnston, 97 cm.) 



The size of the whole nodule varied but very little in the three 

 cases, the first and third being almost identical (about 6 mm.), 

 though the second was larger (15 mm.). The male {see fig. 9), of 

 which a complete specimen has not previously been recorded, was 

 3.8 cm. to 5.3 cm., and in the case of the third nodule above men- 

 tioned 4.6 cm. long. The nodules appear to us undoubtedly to 

 contain either most generally one female only or, less often, one 

 female and one male ; even when no male can be found in the 

 nodule the female is usually fertile, but not invariably so, the fertile 

 ones being found in the smallest nodules. Whether the male has 

 been present and fertilised the female and then left the nodule or 

 degenerated, or occasionally the female is fertilised before the forma- 

 tion of the nodule, or possibly, though it seems improbable, the eggs 

 are produced parthenogenetically, are all matters, at present, of 

 conjecture. Most probably copulation takes place occasionally 

 before the dense nodule wall is produced, though one act of fertilisa- 

 tion seems wholly inadequate to account for the enormous numbers 

 of larvs produced by each worm. This opinion is strengthened 

 by the small number of sterile nodules (we have only found three, 

 out of fully a hundred nodules examined for the purpose, to be 

 sterile), the comparatively rare occurrence of the male in the nodule' 

 and also the apparent absence of any degenerated males in the 

 nodules, while it does not seem possible for a mature worm to make 

 its exit through such a tough, fibrous, wall as that surrounding the 

 nodule. When both worms, male and female, are present their 

 anterior ends have a definite relationship to one another. They lie 

 side by side (see figs. 3, 4, 5, and 37), the female head often slightly 

 in advance of the male, in the same tunnel of the tissue of the 

 nodule, quite on the outermost part of the worm area of the nodule, 

 usually on its flattened surface and more or less towards one side. 

 The two worms (fig. 4) then pass straight across the centre of the 

 nodule to the opposite side, the middle of the male generally lying 

 once coiled alongside and around the female. The hinder end of 

 the male may occupy a tunnel by itself. The female then passes to one 

 end of the outer region of the worm area, along that end and back 

 again along the side to which the heads were pointing ; from this 

 side it enters more deeply into the coil formed by the remainder of 

 its body. The female tail, when found, was at about half-way 

 between the centre and the periphery. 



