4 W. BALDWIN SPENCER. 



that a considerable pull is necessary to dislodge it. When this 

 is done a definite cavity is left^ corresponding in shape and 

 size to the parasite^s head. Not one was found loose in the 

 lung, though the fact that Dr. Baird found his specimen in the 

 mouth shows that they must have the power of becoming free 

 and of movement. Like other parasites, this one seems to try 

 to leave the body on the death of the host. 



3. External Anatomy. 

 (Figs. 1-5.) 



The form of the body is that of an annulated cylinder, 

 bluntly rounded at the anterior and somewhat tapering at the 

 posterior extremity. 



It differs slightly in form and much in size in the two sexes, 

 which can readily, as in other Pentastoma, be distinguished 

 from each other by the position of the opening of the repro- 

 ductive organs. During life the whole body is of a bright red 

 colour, as noted by Baird, the colour being undoubtedly due to 

 the blood sucked in from the lung of the host. 



(i) The Female. — The specimens vary much in size, some 

 being very small and immature, measuring not more than 12 

 mm. in length, whilst a large mature specimen will measure 

 32 mm. in length and 5 mm. in greatest width. Save the 

 anterior end the whole body is annulate, there being 

 from sixty-five to seventy annuli present (sixty-six in the one 

 figured). Occasionally the annuli may be slightly irregular, 

 an incomplete one being wedged in between two perfect ones 



Each annulus consists of an anterior and a posterior portion, 

 and between the two is a slight ridge more or less distinctly 

 marked. This, as will be shown later, can be detected with 

 ease in longitudinal sections. The anterior part corresponds 

 to the annular part, and the posterior to the interannular, as 

 described by Hoyle. With a lens it can easily be seen that 

 the anterior part of each annulus is covered with a number of 

 spots crowded closely together, and showing no arrangement 



