32 MICR0-ORGA.NISMS AS PARASITES. 



man has done, but also to make the result of his investigations 

 clear and plain to any person of ordinary intelligence. 



But many original observers are unable to do this. Each 

 works at his speciality as Oliver Wendell Holmes' immortal 

 "Scarabee," worked at the ^^ larva of Meloce" and they are hardly 

 aware of the magnitude of the coral reef they have been building. 

 Hundreds and thousands of original workers are carrying on their 

 investigations, yet one may search the leading periodicals in vain 

 for any account of the results they have accomplished, probably 

 because some stigma is supposed to attach to the fact of writing 

 upon science without original investigation. Yet we do not say 

 that only generals who have won battles, and politicians who have 

 led senates, must write about history ; we own that the historian 

 has his special work, his peculiar talent. It is time, too, that 

 Natural Science should have her historians ; the glorious work 

 she has done and is doing for men, should be proclaimed, not 

 buried in the pages of scientific journals, to be read only by 

 specialists. 



The Chameleon. — The colour of its skin is changed by virtue 

 of the action of the nervous system on certain little vesicles con- 

 taining pigment, which are in abundance on its surface. These 

 contract when the nerves are excited, and thus squeeze out into a 

 deeper portion of the skin the contained pigment. 



The Nature of Diatoms. — These curiously beautiful micro- 

 scopic objects can be found in the mud at the bottom of all pools 

 of water. They were formerly regarded as animals, but are now 

 classed among plants. Professor W. Mattieu Williams discovered 

 their vegetable character thirty years ago by an observation which 

 amounted to a demonstration. The white quartz pebbles in his 

 aquarium became coated with a brown growth, caused by the 

 development of these organisms, and at the same time evolved 

 bubbles of gas. In the course of a few days, he found an inch of 

 the vertical space of the test-tube, which he fixed to catch it, 

 filled with the gas, and it was proved, by burning wood and other 

 expeciments, to be nearly all oxygen. Animals expire carbonic 

 acid, plants expire oxygen. Therefore, diatoms are plants. 



