226 BULLETIN OF THE BUREAU OF FISHERIES. 
ends penetrate the epithelial layer, and break up into brush-like terminations on its 
surface. 
(17) The kidneys lie dorsal to the pericardial cavity. The main secretory part of 
each kidney is much pouched and lies on the posterior adductor muscle. It is con- 
nected with the posterior ends of the pericardial cavity by a very long, narrow 
duct, and with the exterior by a very long, larger duct which opens under the visceral 
ganglion. 
(18) In the adult ship-worm the sexes are separate. Young individuals (1-4em. 
long) of X. gouldi, however, are very frequently hermaphrodite. In all such cases 
the male cells are developed first, indicating that the species may be protandrous. 
The sexual duct is very short and is formed as an ectodermal invagination. 
LITERATURE. 
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