ASHFORD: THE ACTION OF THE HEART IN THE HELICID^. 325 



It would be unsafe to generalize from observations on two 

 species only, neither of them complete hibernants, still each is, 

 in most respects, a fair representative of its genus, and it is 

 probable that similar results would be obtained from an examina- 

 tion of any other of the half-hardy species. A few isolated records 

 tend to support this view. Thus I have counted in Z. radiatuliis 

 9 pulsations at 27° temp., in Z nitidulus 9 at 31°, in H. sencea 9 

 at 29°, and in the same species 12 at 33 and 17 at 40°. Of the 

 hardy species it is unnecessary to speak. They pursue an active 

 life except in severe weather, and of course their hearts are in 

 action during exercise. There remains then the section of 

 complete hibernants, of these and of the Fupce, whose habits are 

 doubtful, I have nothing to say. Their shells are generally too 

 opaque to admit of direct observation. It would be strange, 

 however, if they differed from the rest except in degree. I see no 

 trustworthy method of arriving at a knowledge of their winter 

 condition unless the ingenious Pulse Indicator can be adapted 

 for experiment upon the lower animals. 



At the lower temperatures not only are the contractions of 

 the heart reduced to few in number, but the character of the 

 movements undergoes a change. A full and deliberate contraction 

 will be followed by one, two or three of very small amplitude, and 

 these again, followed after a pause by another full beat. The 

 intervals of recurrence of these imperfect pulsations are unequal 

 in length. The same irregularity is still more marked under 

 abnormally high temparatures, as when a Zonites has been for a 

 few minutes in a hot-house. The subsiding movements then take 

 the form of true palpitation, and the strenuous efforts of the 

 animal to change its position proves that it is suffering discomfort. 



Though not exactly pertinent to the subject of these notes, I 

 may add that in the case of the Helix liortensis mentioned above, 

 the character of the epiphragm altered with the temperature. 



