^gP''] Field Natiivalists' Club — Proceedings. 71 



grained mass of sub-crystalline mud, and they are all more or 

 less uniformly spaced out from one another. Its history 

 seems to be as follows : — A granular sand was formed by the 

 agency of lowly plants — probably belonging to the blue-green 

 algae — which secreted carbonate of lime from the sea-water in 

 order to make the limy tubular thallus forming the con- 

 centric coats of each grain. Such oolitic grains are now being 

 formed on the shores of the Great Salt Lake of Utah, and in 

 the warm springs of Carlsbad, in Germany. The loose grains 

 were then surrounded by mud, and the spacing by means of 

 spiky crystals developed round each grain took place. The 

 whole was consolidated as a pure limestone. In the course of 

 time flocks of sea-birds found their resting-place on the island, 

 and their droppings formed the guano deposit. The rain 

 which fell upon this guano deposit carried the phosphoric acid 

 downwards into the underlying limestone rock, and a gradual 

 change ensued, resulting in the complete phosphatization of 

 the limestone as it now occurs." 



Adverting to Mr. A. L. Scott's exhibit of crocidolite, Mr. 

 Chapman said : — " The name is derived from ' kroke,' a thread, 

 and not from ' krokoeis,' saffron-coloured, as sometimes sup- 

 posed, for, as a matter of fact, the true crocidolite should show 

 the blue asbestiform and silky character of the mineral, and 

 not the yellow ' cat's-eye ' form. The latter variety is a re- 

 placement of the original silky hornblende or true crocidolite 

 by pseudomorphs in quartz, the quartz fibres being coated at 

 intervals with the hydrated ferric oxide — limonite or yellow 

 ochre. The iron mineral imparts a yellow colour to the 

 mass, in which condition it is called Griqualandite, from its 

 occurrence on the Orange River in Griqualand, South Africa." 



Mr. J. Searle, in calling attention to his exhibit of specimens 

 of volvox under the microscope, said that volvox, though 

 common in most fresh-water pools, was an extremely beautiful 

 object, and of great biological interest. For many years it 

 was claimed by botanists as a green alga, but is now conceded 

 to the zoologists as a flagellate infusorian, occupying a place 

 between the Protozoa and the Metazoa. In the first-named 

 group all the functions of life are carried on within its single 

 cell ; in the Metazoa distinct sets of cells are specialized for 

 various activities ; while volvox consists of a vast number of 

 zoids embedded in a spherical gelatinous mass, each zoid 

 possessing two flagellae, which project thi"ough the gelatinous 

 envelope, and to their regular action the well-known rotary 

 and progressive movements of volvox are due. The sexual 

 colonies of volvox exhibit the beginning of that differentiation 

 between body cells and reproductive cells which becomes more 

 characterized in higher forms of life. 



