72 
ORIGIN OF LIFE IN AMERICA 
It may be of interest now to inquire as to how far a. group 
of less mobile creatures than the mammals, the snails, for 
instance, can be classified into species whose ancestors were 
Asiatic, and such as were originally native to the soil. Of 
course we need only consider snails resident in the Atha- 
baska—Mackenzie Region. A direct European influence 
among the fresh-water molluscan fauna is apparent, since 
certain species such as Limnaea stagnalis, L. truncatula, L. 
palustris, and Aplexa hypnorum inhabit the Mackenzie 
Region as well as Europe. How they have spread to America 
is not readily ascertainable. The points of resemblance 
between the two regions are clearly of long standing, but none 
of these species need necessarily have come from Europe 
direct, as they all inhabit Siberia as well as Canada. 
Among the land snails we also meet with forms familiar 
to the European conchologist, such as Pupa muscorum, 
Cochlicopa lubrica, Hyalinia radiatula, H. nitidula, Euconu- 
lus fulvus, Zonitoides nitidus, and others. All these are no 
doubt very ancient species, too ancient in fact to help us 
materially in our present inquiries. It is possible, moreover, 
that they have special facilities for accidental dispersal, that 
is to say for dispersal other than the ordinary mode of pro¬ 
gression on land, although my studies have not led me 'to 
believe in the efficacy of such a mode of conveyance in 
permanently stocking a country. 
The strictly American Pupa armifera and P. holzingeri, 
Vertigo ventricosa, V. ovata, Vitrina limpida, Patula solitaria, 
and P. striatella are all easily transported by flooded streams, 
and thus scattered far and wide. In spite of the fact that the 
land and fresh-water mollusks of the Mackenzie Region 
indicate that a distinct Old World influence is recognisable, 
nothing points definitely to a recent land connection with 
either Europe or, Asia. They do not confirm the view that any 
survival of the molluscan fauna through the Glacial Epoch 
has taken place in that region. On the contrary, the absence 
of species peculiar to the region implies, as among the 
mammals, that that part of America has only recently been 
stocked with animals from another portion of the continent. 
Whether we assume that gigantic glaciers covered the coun¬ 
try, or whether we argue that the ocean invaded it, the. 
