IN MODERN SCIENCE. 



199 



mass, to have pulsating sacs and reproductive 

 organs, and threadlike flagella wherewith to 

 swim. Their eggs are, of course, much small- 

 er than themselves — so much so that some of 

 them are probably invisible under the highest 

 powers yet employed. Each of them however, 

 is potentially an animal, with all its parts rep- 

 resented structurally in some way. Nor need 

 we wonder at this. It has been calculated that 

 a speck scarcely visible under the most po\/er- 

 ful microscope may contain two million four 

 hundred thousand molecules of protoplasm.* 

 If each of these molecules were a brick, there 

 would be enough of them to build a terrace of 

 twenty-five good dwelling-houses. But this is 

 supposing them to be all alike ; whereas we 

 know that the molecules of albumen are capa- 

 ble of being of very various kinds. Each of 

 these molecules really contains eight hundred 

 and eighty- two ultimate atoms — namely, four 

 hundred of carbon, three hundred and ten of 

 hydrogen, one hundred and twenty of oxygen, 

 fifty of nitrogen, and two of sulphur and phos- 

 phorus. Now, we know that these atoms may 

 be differently "arranged in different molecules, 



* I am indebted for these figures to my friend Dr. S. P. Robins of 

 Montreal. 



