92 
SKATE. 
between the brain and these ducts, but when they divide 
they become suddenly so pellucid, that it is impossible to 
trace them further, or to distinguish them from the coats of 
the ducts. The mucus of these ducts is so extremely viscid 
that it is dilRcult to squeeze it out.” The author further 
remarks on the importance of this secretion of mucus to 
the fish, that so much nervous energy as is shewn by the 
magnitude of the nerves themselves, is required to preside 
over its formation j and he might have added, that this 
secretion appears to go on long after the death of the 
creature, as it does also in some others of this family of 
fishes; for it is in the experience of fishermen, that in pre- 
serving them with salt for their subsistence in winter, to use 
their own phrase, they take salt very slowly. It is found, 
in fact, that a continual flow of this tenacious mucus will 
prevent the actual application of the salt to the surface of 
the skin, so that it becomes necessary to make incisions 
into the flesh for the purpose of preserving it. Several days 
will pass before this preserving process can be said to have 
begun, in consequence of the interposition of this glairy fluid. 
It is not improbable that the salt itself may act as a stimulus 
on the ducts, and thus produce that continued flow of the 
secretion which counteracts its own effects. 
This fish is sometimes found with an irregular formation, 
consisting of an interruption in the continuity of the outline 
reaching from the snout along the anterior border of the 
pectoral fin. Of such a one we give a figure, (page 96,) but 
it is not, as has been supposed, when it has occurred on both 
sides, the mark of a separate species. 
PAEASITE OS THE SKATE. 
(Eirudo muricata,) 
