THE SPINNING SLUG. 539 



pores that covered its whole body. A great degree 

 of exertion seemed necessary to produce a sufficient 

 supply of the liquid, and to force this toward the 

 tail. It alternately pushed out and drew back its 

 head; and turned it as far as possible, first to one 

 side and then to the other, as if thereby to press its 

 sides, and thus promote secretion This motion of 

 the head in an horizontal direction made the whole 

 body turn round ; by which the line, which would 

 have otherwise remained somewhat flat, became 

 round. This motion also, no doubt, in addition to 

 the weight of the animal, tended materially toward 

 lengthening the line*. 



This is the subtance of Mr. Hoy's account. Dr. 

 Latham says that the secretion from which the 

 thread is formed is wholly from the under parts of 

 the animal, and not from the back or sides, both of 

 which, during the operation, appear nearly dry. 

 That it did not proceed from any orifice in the tail 

 was evident ; for in some experiments the anima] 

 was suspended by the tip, and at other times from 

 the side, a full eighth of an inch from the tip. The 

 flow of the viscous secretion toward the tail ap- 

 peared to be excited by means of an undulating 

 motion of the belly, similar to that of crawling. 



After having spun for some time, the power of 

 spinning seems for a while to be lost : but in those 

 slugs on which experiments have been made it has 

 always been recovered, after their being kept some 

 Jiours among wet mossf. 



* Mr. Hoy in Linn. Tran. i. 113. 

 + Latham in Linn. Tran. iv. 85. 



