Quarterly journal of Conc/iology. 415 



aqueous excursions, the habit of spinning is essential to their mode 

 of hfe. 



Lij/uuca stagnalis,* L. palustris,'^ L. auricidaria,\ L. peregra,\ 

 L. gliitinosa,\ Plajiorhis corneiisA — When full grown these species, 

 being much larger and stronger than any of the foregoing, are able 

 to traverse more ground in a given time ; hence they do not feel 

 the necessity of using a thread so often as the smaller species. 



If any of my readers wish to see for themselves- this habit of 

 travelling, as used by the mollusca, let them take a few adult 

 Physa ]typ)ioritni — a species which may be found very early in the 

 spring, and throughout the year, following 



" The melancholy feet 

 Of him that is the father of deca)'. 

 Spoiling at once the sour weed and the sweet." 



place them in a glass vessel with some small pebbles at the bottom 

 and a little weed, which should lie at the bottom, so as to allow 

 a clear space for the threads between it and the surface of the 

 water, and keep them until they deposit spawn. As soon as the 

 young are free from the spawn mass they will commence spinning, 

 and practice it so often that the process may be seen at any 

 time. 



I have only now to add that the nomenclature of the British 

 mollusks named in this paper is that of Dr. Jeffreys (Brit. Con.) 

 Where a foreign species is mentioned the authority is given. 



Feb., 1S7S. 



->♦•-♦- 



* Species I have seen spin a thread. 



f Species I have kept but not seen spin. 



i Species seen to spin by others^ 



