VOL. XVI 

 18U3. 



] PROCEEDINGS OF THE NATIONAL MUSEUM. 367 



are exposed are greater or less. Thus in the Limacidw, whose means 

 of protection and whose chances of i^reservation are much less than 

 tliose of the Helicidcv, the number is much greater than in the latter. 

 The number of eggs produced by two individuals of Limax agrestis 

 kei)t in confinement by Dr. Leach was, in the course of rather more 

 tlian a year, seven hundred and eighty-six. It usually amounts to at 

 least three hundred per annum. The other species, though not equally 

 prolific, mnlti])ly greatly; and each pair of the various species of 

 McHcida' produces, annually, from thirty to one hundred eggs, and 

 perhaps more. The young of the Limacidw complete their growth and 

 reproduce their kind sometimes within the year of their birth, and 

 always as soon as the second year; and the species of the other families 

 are believed not to require a much longer time to attain maturity. 

 This rapid increase replaces the numbers annually destroyed, and 

 maintains tlie species in their relative importance. 



" Their extreme tenacity of life is manifested in every stage of growth 

 from the i^g^ to the mature animal. In the northern part of the United 

 States we have frequently observed the eggs of the Helicidcc in the forest 

 covered with snow, protected only by a single leaf, where they had re- 

 mained through the winter months, constantly exposed to a temperature 

 much below the freezing point. The ^eiici(?rt" themselves withstand the 

 cold of the severest winters in the same situations, and tSuccinca has 

 been frozen in a solid block of ice and yet escaped unharmed. Helices 

 when frozen in a state of confinement, though they sometimes recover so 

 far as to move about with some activity, usually survive butashort time. 



SUBSISTING WITHOUT FOOD. 



"The great length of time they can subsist without food is another 

 exemplification of their great tenacity of life. Those species, especially 

 which live in dry and exposed situations, have the power of endurance 

 to a remarkable degree. A friend received specimens of H. desertoruvi 

 which had been collected in Egypt, had been shipped to Smyrna, thence 

 to Constantinople, thence to Rio Janeiro, and finally to Boston, occu- 

 pying a i)eriod of about seven months, which aj^peared in full vigor 

 when taken from the papers in which they had been enveloped. They 

 were laid away in a drawer, and on being examined three years after- 

 wards some of them still came out in tolerable vigor." 



Further instances of the extraordinary vitality of the land snails 

 have come under my own observation, and these are more directly 

 pertinent because the species referred to are West American, and 

 inhabit areas where the physical features are more nearly like those 

 of the South American mainland, and that particular zone of the 

 same from whence no doubt the Galapagos islands were originally 

 stocked. 



In December, 18G5, the Stearns collection, now in the jSl^ationaJ 



