234 



ON WAX SIMULACRA OF SHELLS. 



diagrams, there are numerous minor or secondary lines, so that 

 each band, or wave of growth, is made up of a number of 

 smaller hands, just as on the sea the larger wave has smaller 

 waves on its surface. 



Text-figure 5. 



Photograph of a spiral ' shell ' in paraffin-wax, resembling a Gastropod, but much 

 flatter : more similar to the operculum of Turbo. 



In the wax imitation of the shell the markings are purely 

 superficial, as shown in text-fig. 3 B. If the layer of wax on the 

 surface of the water at each successive moment of time were 

 solidified before the next were added, the mass would consist of 

 superimposed layers corresponding to the lines of ' growth ' on 

 the surface ; but this is not the case, only the marginal incre- 

 ments are solidified, the internal mass remains as a quantity of 

 liquid wax without structure and cools into a single mass. 



In conclusion it may be pointed out that the only resemblance 

 between the real shells and their wax counterparts, is that they 

 are both formed by successive accretions to the edge : the marks 

 of the boundaries of these accretions are due, in the case of the 

 wax to interruptions of the flow by cooling of the lower layer and 

 surface tension, in the case of the real shell to ' waves' of growth 

 of the causes of which we are quite ignorant. 



The photographs in text-figs. 4 <fc 5 Avere taken by my honorary 

 assistant, Mr. H. G. Billinghurst, to whom also j I am much 

 indebted for assistance in carrying out the experiments. 



