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internal structure is also a subject of a good deal of 

 interest. The stomach of one of the larger ones is 

 exhibited to our wondering eyes, and shown, under the 

 microscope, to be lined by a thin gizzard-like membrane, 

 armed with some thousands of horny teeth, for the 

 purpose of masticating the food ; the stomach being set 

 in motion by a large muscle. 



The pulsation of the heart of these creatures is 

 watched with great interest, and one or two instructive 

 experiments are made upon them. A large specimen of 

 Limacc cinereus is first obtained, and being placed on a 

 plate, or some shallow vessel, is allowed free liberty of 

 action ; this he presently takes advantage of, and stretch- 

 ing himself to his full length, begins his peregrinations ; 

 almost simultaneously with this we perceive his breath- 

 ing hole expand, displaying all the internal structure 

 of that part of the body just beneath the mantle ; the 

 lungs and the heart are easily discernible. Wishing for 

 a closer inspection of these, we apply our magnifying 

 glasses, and thus perceive a sight which astonishes us. 

 The whole arrangement of the heart, with its network 

 of arteries and veins, is rendered quite distinct, and by 

 careful observation, we can discern the repeated filling 

 and emptying of these, as the muscles of the heart 

 expand or contract ; counting the strokes we find that 

 Limax cinereus has a pulsation of 60 or 70 strokes per 

 minute, and this we find to be the ordinary rate of most 

 other land mollusks, under a temperature of about 

 60° Fahrenheit. 



We next place under review several different species 

 of the most transparent Zonites, examining them with 

 a pocket lens. The heart is best seen when the shell 

 is placed with the under surface upwards ; the pulsation 



