with Report on Experiments. 
369 
embryos taken from the earth-worm had slightly increased 
in length. Their heads displayed a mouth, leading to a short, 
straight, and simple oesophageal tube, lined with chitin ; all 
of them presenting more pointed tails than formerly, with their 
ends, in many instances, bent forward like the barb of a fish-hook. 
The internal granules were more crowded, rendering the position 
Fig. 6. — Embryo of Sironcjyle from Fig. 7. — Embryo of Strongylefrom 
the Intestine of an Eartli-ioorm. the Intestine of an Earth-worm. 
Length of an inch. Length -^fj of an inch. 
of the future intestine more conspicuous, though as yet the differ- 
entiation gave no sign of any distinct intestinal wall (Fig. 6). 
The thickness of the body had not correspondingly increased. 
Further Experiments. — The next step consisted in the selec- 
tion and examination of fresh earth-worms from time to time. 
Some of these were purposely infected, and some were not. In 
this way I had repeated opportunities of confirming the results 
