IANTHINA. 185 



know that gardeners can produce differently tinted 

 flowers in an Hydrangea or a Dahlia by the empirical 

 application to the soil of certain mineral admixtures. 

 Cannot Nature do as much for marine animals by a 

 prescient combination of similar ingredients in the sea- 

 water ? With respect to shells Mr. C. Stewart has satis- 

 fied me that Littorina obtusata, when calcined or even 

 subjected to the heat of a lamp-flame, quite loses its 

 colour, which, he remarks, would not be the case if that 

 colour had a mineral for its base. But many minerals 

 possess an intense colour which they lose entirely when 

 heated to a certain temperature. This phenomenon has 

 been lately explained by M. Wyrouroff of Moscow in the 

 Bulletin of the Chemical Society of Paris. The late 

 Professor Forchhammer, in a lecture on the metals in 

 ashes of plants (Report of the Danish Association of 

 Agriculturists, 1855) stated that manganese constitutes 

 the colouring-matter of the brown rings or bands and 

 lip of certain snails (e. g. Helix nemoralis) , the snail 

 getting the manganese from the plants on which it feeds, 

 and these again from the soil. He also confirmed a 

 discovery previously made by chemists, that the field and 

 garden slugs contain copper, which occurs in wheat and 

 other cultivated plants. Here I must for the present 

 leave the question. The oceanic distribution oflanthina 

 is coextensive with that of the temperate and torrid 

 zones, although it especially frequents the latter. None 

 have been found in the arctic or antarctic seas, or in a 

 fossil state. Five species occasionally visit our shores, 

 being brought hither by the Gulf-stream and a continu- 

 ance of westerly gales. One only I regard as British, 

 and that not without considerable doubt. 



The systematic position of the genus is scarcely set- 

 tled. Its founder, Bolten, associated with it several 



