246 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



exterior by a small oval aperture situated just above and 

 behind the dorsal end of the neuropodium (fourth to 

 ninth). 



Immediately behind the posterior part of the funnel 

 there is a small pinkish ovoid, club-shaped or cylindrical 

 mass of cells. This is one of the reproductive organs of 

 the worm, an ovary or testis as the case may be. There 

 is no gonad on the first nephridium. 



The funnel and anterior part of the excretory portion 

 of the organ are attached to the body wall by a thin 

 mesentery, and the funnel is further held in its place by 

 one of the oblique muscles which crosses it and is fused 

 to it. 



The nephrostomes of the ' first pair of nephridia are 

 situated on the anterior face of the third diaphragm. 

 They are somewhat smaller than those of succeeding 

 nephridia (fig. 27). The first and last pairs of nephridia 

 are subject to considerable variation, and the former 

 especially are often appreciably smaller than any of the 

 succeeding nephridia. Out of about 160 specimens ex- 

 amined eight were found in which there is some departure 

 from the normal condition. Six of these specimens 

 show reduction or loss of the first nephridium. In one 

 example the first nephridium of each side is very small, 

 its secreting portion being only as thick as an ordinaiy 

 pin ; in the second example the first left nephridium is 

 normal but the right one has no funnel ; in the third case 

 the first nephridium on each side has no funnel ; in the 

 fourth and fifth examples the first nephridium of one side 

 has a very small funnel while the corresponding one of the 

 other side is represented by a funnel only; and in the 

 sixth specimen the first left nephridium is totally sup- 

 pressed, the corresponding right one being present, but 

 Avithout funnel. In the other two cases of variation the 



