32 
the vitelline duct, the uterus winds in a few loops greatly distended 
here and there by the enormous eggs and not extending behind the 
testes. It then runs up straight as a strongly muscular vagina, 
armed with spines similar to those in the cirrus but rather thinner 
and not so closely set, to open into the genital sinus. 
The eggs, seldom more than four, although eight have been 
observed, are relatively very large, measuring 0-08 mm. to 010 mm. 
in length, the breadth being about two-thirds of the length. In the 
smaller specimens the eggs give the worm a most curious appear- 
ance, as they are as large as the testes. The smallest specimens 
(preserved) containing ova measured 0*54 mm. in length. Younger 
stages from the mouth and stomach of the Catfish measured 0-34 
mm. to 050 mm. in length, and can be traced from the young stages 
without vitellaria onwards. 
The life history appears to be fairly clear, as a cercaria corres- 
ponding in every way to these young stages from the Catfish occurs 
in the liver of Buccinum undatum. This cercaria was first described 
by myself from Holy Island (3), but further infected specimens of 
Buccinum have been met with about two miles north of Cullercoats 
Bay, and from these I am able to give an amended description, and 
can correct certain errors in the first. 
80 specimens of Buccinum undatum were collected in March, 
1910, and in six of these the liver was of an unhealthy brownish 
colour all over, the reproductive organs in addition being imperfectly 
developed. The worm occurred throughout the liver which was 
literally packed with rediae. I formerly described these rediae as 
sporocysts since the small mouth and pharynx with the sac-like 
intestine, which are undoubtedly present, were not then noticed. 
The youngest redia (fig. 3) seen measured 0’30 mm. in length 
when alive, and was quite colourless. The mouth led to a muscular 
pharynx and intestine reaching more than half way down the body. 
The hind end was pointed, and there were no locomotory processes 
posteriorly which are often so conspicuous in the young redia, and 
there was no collar anteriorly. It is possible that the absence of 
these appendages shows that the redia is developed in the same 
organ as the sporocysts, and that it does not migrate, as is often 
the case, from one organ to another. This small redia contained no 
cercariae. The larger rediae (figs. 4-5), which measure 0-50 to 3-20 
mm. in length, were either very short and sausage-shaped and 
contained two or more cercariae, or they were elongated and con- 
tained from 16 to 32 cercaria. These older forms were of a dull 
