7(/r</.s<V(.s nf ihc Cockle and Mussef. I't'l 



muscular })Ii.irvn\ [jih.) uicasuiin^ •().") x "O^ nun. '1 liis 

 is roiitinutil l)y a narrow slraijjjlit d'sopluij^us, wliicli remains 

 undivided until near the vi-niral sucker, where it bil'ureales 

 into two diverticula (PI. iV. tig. 5, dig.). 



The excretory system (fig. 5, ex.) is well-marked. It is 

 loaded wiih head-like globules, which disappear on treatment 

 with acid. There are two main tubes of varying width 

 running almost the whole length of the body and uniting 

 posteriorly in a vesicle w hich opens terminally i)y an excretory 

 ]>ore. Anteriorly the main tubes receive numerous short, 

 simple brandies. 



On more minute examination an extremely narrow tubule 

 (PI. IV. fig. 5,/./.) can be discerned to the outer side of each 

 main excretory tuljc. They are i)rovi(ied witli flaiiic-tlagella 

 and have ajjparently some connexion with the excretory 

 system, although their exact relation could not be observed. 



Genital organs are not yet present, but sperm-cells are 

 apparently developed. They occur diffusely. Ou rupture of 

 the animal by pressure these cells issue in great numbers. 

 They are evidently spermatozoa, for they possess a head 

 and vibratile tail, and execute the typical spermatozoid 

 movements. 



The adult stage (PI. IV. fig. 6) of tliis parasite is to be 

 found in the oyster-catcher {Hceinatopus ostraltyus). 1 had 

 an opportunity * of examining many of the birds that fre- 

 quent the shores of the Eden estuary, but in most of thcni 

 only cestode jjaiasites were to be found. In the oyster- 

 catcher, besides the usual collection of tapeworms, several 

 Trematodcs were found in the intestine. The stomach is 

 generally full of the remains of cockles and mussels, and the 

 gut contains numerous cysts similar to those found in the 

 cockle. Towards the lower end of the intestine the desired 

 parasites were obtained. They arc not at all of frequent 

 occurrence, but being translucent and of no great size they 

 may easily escape notice. 



The adult resembles the encysted larva to a marked dc<'rcc, 

 the main external point of difference being the elongation of 

 the posterior part of the body. The distance between the 

 two suckers remains practically the same, as does the average 

 breadth of the animal, the whole length being increiised to 

 about 1;25 mm. 



This parasite has several features in common with the 

 members of the Trcmatode subgenus Echinostomum (cf. 



* For this I nni ind-ltt-tl to uiy fiicnds Messrs. II. M. Craifj: aud 

 Arthur Mills and to Mr. A. W. lirowu, of the Gatty Marine Luboiutoiy. 



