318 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. — 
brane encloses a second and slightly larger periproctal 
sinus. 
The fluid which fills the body cavity and sinuses has a 
peculiar musk-like odour, and is of a pale greyish red 
colour. It contains a small quantity of albuminoid matter, 
and has an alkaline reaction. Its specific gravity is the 
same as that of sea-water. Corpuscles of two kinds are 
found in it. One of these is a colourless amceboid cell, 
the finely granular protoplasm of which throws out long 
filiform and branched pseudopodia. The pseudopodia 
unite with those of other cells with which they come in 
contact. This is followed by coalescence of the cell bodies, 
and the process is repeated until large plasmodia are 
formed, in which an endosare and ectosare become dif- 
ferentiated. ‘The second and rarer kind is a larger cell, 
also colourless, and containing a number of large, spherical 
refractive granules. The ccelomic fluid coagulates rapidly 
when drawn from the test, and a clot 1s formed consisting 
of a clear substance, allied to mucine, in which all the 
corpuscles are included. 
REPRODUCTIVE SYSTEM. 
The reproductive organs or gonads are five arborescent 
glands, suspended by mesenteric folds from the inner wall 
of the apical half of the test (Pl. V., fig. 37, gon.), and are 
very similar in position and appearance in the two sexes. 
They are interradial, and open to the exterior through the 
pores of the basal plates of the apical system. Before 
reaching their respective pores, the five genital ducts 
perforate a ring-like coelomic sinus which encircles the 
rectum. This is readily seen in young specimens in which 
the gonads are not ripe. The walls of the gonads are 
extensively sacculated, and form numerous follicles, on 
the inner surface of which the sexual cells are formed 
