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 difficult 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; and he might have added, that this 

 secretion ajDpears 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. 



PARASITE ON THE SKATE. 

 ( Ifirudn muricata.) 



