4oS Quarterly Journal of Conchology. 



Having thus far, I hope, succeeded in indicating the " why 

 and the wherefore " of moUuscan threads, I will tabulate the 

 species I have seen spin and those seen by others, commencing 

 with the species that spins oftehest and best, and relate one or 

 two incidents connected therewith. 



Pulmonobranchiata. 



Physa hypnorum. — As before stated, I have had the young 

 of this species creeping up and down permanent threads for 

 eighteen or twenty days together. In one case I saw three Physae 

 and a Liinncea glabra upon a thread of the former at one time. 

 Often, when two Physse meet upon the same thread, they fight as 

 only mollusks of this genus can, and the manoeuvres they go through 

 upon their fairy ladders outdo the cleverest human gymnast that 

 ever performed. I once saw one ascending, and when it was half 

 way up the thread it was overtaken by another; then came the 

 "tug of war"; each tried to shake the other off, by repeated 

 blows and jerks of its shell, at the same time creeping over each 

 others shell and body in the most excited manner. Neither 

 being able to gain the mastery, one began to descend, followed by 

 the other, which overtook it, reaching the bottom first. Yet they 

 are not always bent upon war, but pass and repass each other in 

 an amicable spirit. One of the most beautiful sights in moUuscan 

 economy is to see these little "golden pippins" gliding through 

 the water by no visible means; and when they fight, to see them 

 twist and twirl, performing such quick and curious evolutions, 

 while seemingly floating in mid-water, is astonishing, even to the 

 patient student of Nature's wonders. 



If when one of these mollusks is ascending by a thread, it be 

 disturbed sufficiently to cause it to descend before reaching the 

 surface of the water, it changes the point of attachment of its 

 thread from the tail to the head, by bringing its extremities 

 together, the alteration of position being attained with great 

 dexterity and ease. 



