STUDIES IN" ANIMAL LIFE. 35 



instinctively bury themselves in damp ground, and 

 I therefore instituted a series of experiments by 

 placing the newly-emigrated worms in flower-pots 

 filled with damp earth. To my delight, I soon per- 

 ceived that they began to bore with their heads into 

 the earth, and by degrees drew themselves entirely 

 in. For many months I kept the earth in the flow- 

 er-pots moderately moist, and, on examining the 

 worms from time to time, I found they had gradu- 

 ally attained their sex-development, and eggs were 

 deposited in hundreds. Toward the conclusion of 

 winter I could succeed in detecting the commencing 

 development of the embryos in these eggs. By the 

 end of spring they were fully formed, and many of 

 them, having left their shells, were to be seen creep- 

 ing about the earth. I now conjectured that these 

 young worms would be impelled by their instincts 

 to pursue a parasitic existence, and to seek out an 

 animal to inhabit and to grow to maturity in ; and 

 it seemed not improbable that the brood I had 

 reared would, like their parents, thrive best in the 

 caterpillar. In order, therefore, to induce my young 

 brood to immigrate, I procured a number of very 

 small caterpillars, which the first spring sunshine 

 had just called into life. For the purpose of my 

 experiment, I filled a watch-glass with damp earth, 

 taking it from among the flower-pots where the 

 thread-worms had wintered. Upon this I placed 

 several of the young caterpillars." The result was 

 as he expected; the caterpillars were soon bored 



