318 
Distoma luteiim n. sp. etc. 
slowly in its capsule, and well cliai’acterised by an arc of spines in a 
double row situated along the anterior dorsal edge, and reflected over 
on each side ventrally for a short distance, where it consisted of two or 
three spines oidy; minute spines also appeared on the dorsal surface 
of the body. Two rows of clear oily looking cystogenous cells were 
observed in all. Such spines were never observed in the free swimming 
cercariae. 
Fluke or Adult Stage. 
The next stage in the life history of the encysted cercariae was 
probably to be found in some animal which lived on the snails, and, as 
the lake abounded with frogs {Rana and Xeno-pus) these were naturally 
suspected to act as the next host for the parasite. A number of these 
frogs were dissected, and it was ascertained that both kinds fed exten¬ 
sively on the snails. Among the many kinds of parasites (protozoa, 
round and flat worms) found in the alimentary tract of the frog were a 
number of flukes, which were very abundant, differing however from 
the encysted form in that they had no strong anterior spines, but a 
great number of small spines arranged in closely set rows (about 40 to 60) 
on the dorsal and extending to the ventro-lateral sides of the body. The 
largest of these flukes were about T2 mm. in length and 0-32 mm. in 
breadth. They were of a yellowish colour and some had well developed 
ova. The species is nearly related to Distoma echinatum, but, as the 
intermediate stage differs somewhat from that of the latter, which 
moreover is never found in a cold blooded animal, we must regard this 
as jrrobably a new species, which may be called D. luteuni. 
In order to trace the various stages, and to ascertain if these were 
the adults of the encysted form a number of feeding experiments were 
carried out. Some frogs, after being kept without food for a time, 
were given some of the snails in which cysts, as well as rediae and cer¬ 
cariae, occurred. A frog, dissected shortly afterwards, still had the 
snail in its stomach; the cysts were unchanged though the rediae and 
cercariae were digested. Another frog, examined about six hours 
afterwards, had the remains of the snail with the group of cysts in the 
small intestine, about half way to the rectum, and, in some cases, the 
fluke was found in the act of escaping from the cyst, sometimes head 
first and sometimes tail first, while others had apparently been free 
for some time and were moving about actively. These were of particular 
interest as they possessed the large oral spines of the encysted forms, 
and the small dorsal spines of the fluke above mentioned. This experi- 
