NONSUCH 



find it is actually sunken in a shallow pit — another 

 guard against being swept out to sea. This implies 

 a permanent residence of sorts and then we re- 

 member that Aristotle, two thousand years ago, 

 knew and wrote about the daily grazing excursions 

 of the limpets. When the pounding of the waves 

 eases somewhat, they leave their forms and hastily 

 crawl about, swinging their tiny many-toothed 

 scythe, and cutting a swath through the seaweed 

 fields as they go ; then they return, how, we do not 

 know ; whether by retracing their glairy trail, or by 

 the dim remembrance of crags and valleys, or by 

 some strange memory of place, a homing quality of 

 the little snail's ganglion. 



The simplicity of the outward appearance of the 

 limpet's tent is deceiving, for it belongs to the 

 helices or twisted spirals and its young show distinct 

 coils. Associated with the limpets, on the same 

 rocks, are chitons or armadillo snails which have 

 eight, hard, transverse plates in a line, as unlike an 

 ordinary snail as may be. They cling tightly, and 

 when pried off, curl up like a pill-bug, or an arma- 

 dillo. In my brief resume of devolution I have said 

 there was a time when my ancestors had many more 

 ribs than I, and this repetition of similar parts is 

 an almost certain sign of lowness of type. The 

 chitons are the only snails with more than one shell ; 

 they have eight, and all quite untwisted, in a straight 

 line like the snails of the precambrian days. 



Here then we have mussels, periwinkles, limpets 

 and chitons, all living close to the shore, all pro- 



216 



