1004 MR. R. J. ORTLEPP ON THE 



further study of this, and the rest of the material it was necessary 

 to render them transparent by some clearing medium. Langeron's 

 lactophenol was at first used, but, although this medium is 

 excellent for small nematodes, it did not give satisfactory results: 

 with the larger members of this group, as it did not render the 

 specimen clear enough to make out the details of the spicules. 

 Consequently beech wood creosote was used in its stead. In using 

 this latter medium, the parasites were transferred into strong- 

 alcohol, about 95 per cent., and left therein for a longer or 

 shorter period according to the size of the worms ; after a 

 sufficient interval to allow for the thorough penetration of this 

 alcohol, they were placed in the creosote and examined, when 

 clear, under tlie microscope by placing them on a larger slide 

 and rolling them under a coverslip when necessary. After exami- 

 nation it is essential to remove the creosote from the worms, as 

 they tend to become very dark in colour if returned into the 

 preserving fluid v/ithout removal of the creosote. To obviate 

 this, the parasites were first immersed for at least two hours in a 

 1-2 per cent, acid alcohol solution (70 per cent.), after which 

 they could be transferred into the preserving fluid with apparent 

 safety. 



All the measurements, except that of the length of the worms, 

 were taken by means of an ocular micrometer, the value of each 

 of whose divisions had been previously determined. 



The details of the female genitalia were made out in most 

 species by simple clearing and rolling of the parasites ; in the 

 remaining species it was necessaiy to dissect out these uteri 

 under a dissecting microscope, and to examine them separately 

 when mounted on a slide : where, however, there was ample 

 material of the former, the genitalia were also dissected out. 



Where there was sufficient material a.vailable, the details of 

 the lips were determined by first cutting the lips off from the 

 body and then examining each lip from the inner and outer 

 surface when cleared and mounted on a slide. 



All the figures except one — caudal bursa of Ph. coluhri — are 

 original. All those accompanied by a scale were drawn by means 

 of a camera lucida ; the others are free-hand drawings made 

 from the specimens. 



General Characters of Physaloptera. 



These worms are rounded elongate and taper gradually in their 

 anterior half and posterior third ; they vary considerably in size, 

 the largest specimens known being 10 em. long and nearly 3 mm. 

 thick. The cuticle is loosely attached to the body, and in nearly 

 all cases is extended over the lips to form a prepuce-like collar ; 

 in a few species a similar reduplication is present over the caudal 

 extremities of both sexes. The cuticle always shows a veiy fine 

 transverse striation, which often requires high magnification for 

 its detection. 



