2 EARLY DISCOVERIES. 



to be discernible by the unassisted eye, there would be at least 

 some knowledge of their existence even in the earliest times. 

 But it was not until the invention of the microscope had given 

 to man the means of penetrating the mysterious depths of this 

 diminutive creation that any definite knowledge was obtained, 

 either of its vast extent or of the exceeding wonderfulness of the 

 beings which composed it; while almost every improvement 

 which has subsequently been made in the construction of the 

 microscope has largely added to the wonders which the instru- 

 ment has here revealed. 



The earliest microscopical observations of importance on these 

 minute beings were made by Leeuwenhoek in the latter half of 

 the seventeenth century ; but it was not until a much later period 

 that this branch of study excited any great amount of interest, or 

 was prosecuted with anything like persevering zeal. It was 

 towards the middle of the last century that the great stimulus 

 was given to researches of the kind, by the publication of the cele- 

 brated memoir of H. Trembley, of Geneva, on the little Hydra, 

 or fresh-water polyp of our ponds and ditches an animal whose 

 extraordinary history read, and, indeed, still reads, more like 

 an extravagant romance than a sober recital of actual facts. The 

 publication of this work marks one of the most important epochs 

 in the history of microscopical inquiry, and speedily turned the 

 attention of observers in all parts of Europe to the abounding 

 marvels of the waters. 



Nor is it at all remarkable that such should have been the result ; 

 for this same Hydra is one of a race of animals of which, up to 

 that time, naturalists had been almost wholly ignorant, while the 

 details that were given of its habits and economy were such as 

 completely upset most of the prevailing notions as to the dis- 

 tinctive characteristics of animal life. For here was an animal 

 whose young grew out from its sides like buds from the stem of 

 a plant that might not only be cut into pieces without being 

 killed, but would reproduce a perfect animal similar to itself from 

 every fragment of its original substance that might be turned 

 inside out, and yet suffer no detriment to its powers of digestion 

 that might, in fact, be mutilated and operated upon in almost 

 any conceivable fashion, not only without apparent injury, but 

 without, or at all seriously, interfering with the functions of active 

 life. It ia no wonder, therefore, that observers were everywhere 



