THE BUDDING-OUT OF NEW ANIMALS 57 



the barbs of a feather ; in both cases the hooks can be 

 adjusted rapidly and completely by stroking- from base 

 to tip, and in both a water-tight junction is obtained. 

 Besides the central canal, along which fluids are sucked 

 up, there are lateral canals (tracheae) filled with air. 



Reaumur was careful to correct his anatomical 

 studies by close observation of the live insect. He 

 reared an angle-shades moth, which he kept several 

 days without food. When he saw it repeatedly extend- 

 ing its proboscis, he put near it a piece of sugar. The 

 moth at once began to suck, and became so absorbed 

 in satisfying its hunger that it allowed Reaumur to 

 carry it on a sheet of paper to a window and to examine 

 it closely with a lens. The proboscis was sometimes 

 extended for several minutes at a time, and then rolled 

 up for an instant ; its tip was either employed in explor- 

 ing the surface or closely applied to the sugar. By 

 means of the lens a slender column of liquid was seen 

 to pass along the central canal towards the head. Now 

 and then, however, a limpid fluid was seen to pass 

 down the proboscis ; this was the saliva which was 

 used to moisten the sugar, and then sucked up again. 



The Budding-out of New Animals (Hydra) : another 

 Form of Propagation without Mating (Aphids). 



In the year 1744 a young Genevese, Abraham 

 Trembley, tutor in the family of Bentinck, who was 

 then English resident at the Hague, rose into sudden 

 fame by a solid and well-timed contribution to natural 

 history. Trembley and his pupils used to fish for 

 aquatic insects in the ponds belonging to the residence, 

 and in the summer of 1740 he happened to collect some 

 water-weeds, which he put into a glass vessel and set 

 in a window. When the floating objects had come to 



