■I'AYi.oR : luoi.ocv nv the :\roLi.uscA. 271 



active motion //! aspersa can travel one yard in twelve minutes, or at 

 the rate of a mile in a little over a fortnight • but at times its motions 

 are much more deliberate, and may be no quicker than at the rate of 

 a mile in nineteen weeks. 



Tlie speed is greatly influenced, however, by the nature of the 

 ground over which the creature crawls, as before it can be traversed 

 it must be smeared with mucus or slime, which is poured out by a 

 large gland, opening in front of the animal, and forms the track upon 

 w:hich the moUusk crawls, reminding one of the patent said to have 

 been taken out for an engine to run along the roads and lay down 

 in front as it ran the lines upon which it travelled. 



Judging from the weights this creature can carry without diminu- 

 tion of speed, it would appear to have a great reserve of strength, as 

 it can travel along a horizontal surface bearing or drawing a weight 

 ■fifty times its own, or ascend vertically carrying a weight nine times 

 that of animal and shell combined, which is equivalent to a person, 

 like myself, ascending a ladder with a burthen of nearly a ton, or on 

 fairly level grouiid being able to carry a weight of about four tons. 



Circulation of the Blood and Respiration are co-dependent and 

 influenced by temperature, age and muscular movement. Respiration 

 or breathing in this species averages about four inspirations per 

 minute in summer, but oxidation is not confined to the lungs of the 

 animal, as the skin and tissues are permeated by various substances 

 or pigments, called Enterochlorophylls, which form combinations 

 with and draw oxygen within the system. 



The Heart, which is the source of circulatory activity, is not, like 

 that of man, practically uniform in action at all temperatures, but 

 fluctuates with and is dependent in its rapidity upon the degree of 

 warmth to whicli the animal is exposed, and we may therefore expect 

 what actually does take place — a very marked diurnal range in the 

 rapidity of the heart's action. . . 



On an ordinary summer's day, the heart will vary in the number of 

 pulsations from thirty to sixty or more per minute. A young indi- 

 vidual, whose heart is pulsating at about seventy times per minute, 

 will rapidly increase that number to iio or even more on being 

 placed on the palm of the hand, and that number can be as quickly 

 reduced to twenty or even ten per minute, by placing the creature in 

 contact with a cold surface, until at a few degrees below freezing 

 they are reduced to three or four per minute, and these of feeble 

 character and small amplitude. 



The heart is also very responsive to muscular movement, like our 

 own.' A snail, whose heart was pulsating sixty times j)er minute while 

 arrest, immediately increased the rate to eighty when it prepared to 

 emerge from its shell. 



R 



