Natural History of Molluscous Animals. 523 



In 1819, swallows were gone from our own neighbour- 

 hood on the 29th of September, and martens Oct. 5th; 

 yet on the 29th of October two swallows appeared durmg a 

 snow shower. They settled wherever they could find a place, 

 lying on the belly, as if the feet were benumbed. They 

 finally passed onward to the west. — 1825. Oct. 12. Two 

 martens were seen ten days after all our residents had 

 departed; the same happened two days after. — 1827. Our 

 resident martens went off on October the 14th; and on the 

 29th of November two of that species arrived in the after- 

 noon, and continued hawking for flies. In the previous week 

 there had been frost and snow, with the thermometer 44° at 

 noon. The previous night was a storm ; the same day the 

 thermometer 51°. Probably these birds had been blown out 

 of their course. — 1828. Our residents departed on October 

 11 th; but on November 9th a few appeared. — 1829. Martens 

 decreased gradually until only four couple remained, which 

 went off on October 11th; on the 27th, five birds appeared at 

 about 11 o'clock, sporting about after flies. — 1830. Our resi- 

 dent martens disappeared on October 1 1 th ; but a single bird 

 appeared on December 13th ; the thermometer in the morn- 

 ing 38°, with frost. I was informed that a small flock was 

 seen at Looe a few days previously, and a single one on the 

 16th. No one can suppose that these birds had remained 

 through becoming torpid; for the weather had been mild, 

 and that which I saw appeared on the only cold day we had 

 had. The latter (single) bird seemed in no haste to go off; 

 and I feel inclined to conclude that when instinct has been 

 crossed or not obeyed at its first influence, the individual may 

 cease to be influenced by it, and suffer on that account. It 

 cannot be considered probable that these birds lie hid in tor- 

 pidity for a month or more of mild weather, and then sud- 

 denly appear in that which is colder. J. C. 

 Polperro, Cor?iwall, June 22. 1831. 



Art. XI. An Introduction to the Natural History of Molluscous 

 Animals. In a Series of Letters. By G. J. 



Letter 8. On their Nervous System and Senses. 



"When we are in perfecthealth and spirits,"saysDr.Paley, 

 " we feel in ourselves a happiness independent of any parti- 

 cular outward gratification whatever, and of which we can 

 give no account. This is an enjoyment which the Deity has 

 annexed to life, and probably constitutes, in a great measure, 

 the happiness of infants and brutes, especially of the lower 



