114 



He then spoke of the researclies of Mayer and Ralfs upon this 

 subject^ and pointed out the nature of the test they proposed. 

 This was essentially a chemical test. It was well known that 

 all vegetables more or less secreted starch, or a substance 

 which could be converted into starch by the agency of sul- 

 phuric acid. Tincture of Iodine rendered starch blue : if, 

 therefore, on the application of this substance any so called 

 animalcule turned blue, or had blue spots in its interior — if at 

 the same time it could be shown there was no means by which 

 starch could have been introduced from without — the indi- 

 vidual might at once be put down as belonging to the 

 vegetable kingdom. This test had now been applied to many 

 creatures supposed by Ehrenberg to be animal, and had proved 

 them to belong to the lowest forms of the vegetable world. 



This point, ingenious though it was, and conclusive in its 

 nature, did not apply to those aquatic things which did not 

 produce starch ; and there was still in the minds of some a 

 doubt about the proper locality of the sponge. 



The power of abstracting silex from its combinations was 

 very remarkable both in the lower forms of animal and 

 vegetable life ; the sponge contained an enormous quantity in 

 the form of spicules, and so did many alcyonia. The genus 

 Navicula, which had a silecious lorica or shell, and which he 

 considered as vegetable, not only could appropriate silex from 

 solutions, but it was enabled to dissolve large fragments of 

 sand and to reapply this to the formation of its external shell. 

 In the interior of the shells of this genus, he had often seen 

 grains of sand varying in appearance from a large shapeless 

 angular mass to a minute round spec. This was proved to be 

 silica, by its resisting heat and nitric acid. 



Some mosses had the power of dissolving and appropriating 

 the silex in glass. 



The author quoted largely from Ralfs' " Desmidise,*' and 

 other works on the same subject. 



