ON WAX SIMULACRA OF SHELLS. 225 



17. The Artificial Formation from Paraffin Wax of 

 Structures resembling Molluscan Shells. By J. T. 

 Cunningham, M.A., F.Z.S. 



[Received January 26, 1915 : Read March 23, 1915.] 



(Text-figures 1-5.) 



In December last Mr. R. H. Burne exhibited before this 

 Society some specimens of forms assumed by paraffin-wax when 

 cooled, which resembled in a stinking way in shape and markings 

 the shells of Molluscs. These specimens were presented to 

 Mr. Burne by Hen - C. U. Ariens Kaplers, of the Sencken- 

 bergisches Institut, Frankfurt a. M., and they are described by 

 him in a paper published in the Zeitschrift fur Allgemeine 

 Physiologie in 1907. In that paper no information is given 

 concerning the conditions under which these structures are 

 formed, it being merely stated that they are produced when the 

 melted paraffin-wax solidifies. The shells imitated are stated 

 to be Lamellibranchs, Gastropods (operculum of Turbo), and 

 Brachiopoda. Seeking the explanation of these resemblances, 

 Herr Kappers adopts the conclusion of Harting and Bedermann 

 that the form and characters of molluscan shells, as well as 

 those of otoliths, egg-shells, and the skeletons of Foraminifera, 

 Alcyonaria, and Echinoderma, are due to the aggregation of 

 crystals of calcium salts formed within a colloid medium, the 

 crystals being of a special kind called spheero-crystals or calco- 

 sphaarites. He maintains that paraffin-wax shares with calcium 

 salts the property of forming sphserocrystals, and that the forma- 

 tion of crystals from a solution takes place in essentially the 

 same way as in the solidification of a molten mass. Moreover, 

 there is a further resemblance in the viscosity of the mother 

 liquid, the form which a crystal assumes being more or less 

 influenced by the resistance which its particles encounter in its 

 formation. In molten substances unequal terminal surfaces of 

 the crystals, causing bending and distortion of the forms of the 

 larger crystals formed by means of the smaller, also occur as in 

 viscous solutions. 



Kappers believes that the rapid cooling which is specially 

 effected for histological purposes is favourable to the production 

 of the forms under discussion, because the crystals are then 

 formed in the viscous medium of the cooling substance, whereas 

 in slow cooling normal crystals have time to form. It will be 

 seen below that my experiments are in contradiction to this, for 

 if the melting-point of the paraffin is high it is more difficult to 

 obtain shell-like masses. 



In the discussion that followed Mr. Burne's exhibition and 

 description of the specimens exhibited, I expressed the conclusion 

 from the appearance of the specimens that their form and 



