422 
Marine Cereariae 
2. Developed in rediae. 
(a) Gercaria neptuneae. Cercaria developed in redia in a Gastro¬ 
pod, very thick and large tail, two eye-spots present. Stylet glands (?) 
and cystogenous glands. Excretory vesicle very thick-walled. 
Further life-history unknown. 
(b) AcantJiopsolus. Cercaria developed in redia in a Gastropod, 
two eye-spots, intestinal lobes reaching nearly to posterior end of body, 
thin tail developed in young forms which is cast off before it is full 
grown. 
Encysted stage and intermediate host probably omitted. 
Final host—a fish. 
(c) Echinostoinum group. Cercaria developed in redia in a 
Gastropod. Redia usually coloured yellow or orange, provided with 
a collar, birth-pore and ambulatory processes. Cercaria with well- 
marked head end provided with crown of spines. Intestinal lobes 
reaching nearly to posterior end of body. Excretory system with small 
posterior vesicle and two conspicuous lateral canals. Tail long and 
narrow. Free-swimming stage. 
Intermediate host—a Mollusk or fish. 
Final host—Mammal, bird or fish. 
B. (With one sucker only.) 
{d) Monostomum group. Cercaria developed in rediae in a Gastro¬ 
pod. Eye-spots, tail long. Free-swimming stage. Encysted stage 
perhaps free. 
Final host—a bird or fish. 
Description of Matericd. 
Nearly all the cereariae referred to in the following notes have been 
seen by myself and drawings made from the living objects. A few 
have been copied from others when I could not get specimens, and for 
these I have to thank Dr William Nicoll and Mr Jas. Johnstone. 
Most of the work has been carried on at the Dove Marine 
Laboratory, Cullercoats, through the kindness of Armstrong College, 
Newcastle-upon-Tyne. Part of it was done at the Marine Station, 
Millport, and the Marine Laboratory, Plymouth, and I have also done 
a good deal of it at Leeds University. 
In the course of my work I have examined material at many 
different times of year, and find that in nearly every case the sporocysts, 
