5 2 Life and Immortality. 



posterior end of the body. But this curious structure, as 

 shown by Claparede, merely consists of a deep longitudinal 

 involution of the walls of the intestine, by which means an 

 extensive absorbent surface is secured. 



Worms have a well-developed circulating system. Their 

 breathing is effected by the skin, and so they do not possess 

 any special respiratory apparatus. Each individual unites 

 the two sexes in its own body, but two individuals pair 

 together. The nervous system is fairly well developed, the 

 two nearly confluent cerebral ganglia being situated very 

 close to the anterior extremity of the body. 



Being destitute of eyes, we would naturally conclude that 

 worms were quite insensible to light ; but from many experi- 

 ments that have been made by Darwin, Hofmeister and 

 others, it is evident that light affects them, but only by its 

 intensity and duration. It is the anterior extremity of the 

 body, where the cerebral ganglia lie, that is affected, for if 

 this part is shaded and other parts of the body are illumi- 

 nated no effect will be produced. As these animals have no 

 eyes, it is probable that the light passes through their skins 

 and excites in some manner their cerebral ganglia. When 

 worms are employed in dragging leaves into their burrows 

 or in eating them, and even during the brief intervals of rest 

 from their labors, they either do not perceive the light or are 

 regardless of it, and this is even the case when the light is 

 concentrated upon them through a large lens. Paired indi- 

 viduals will remain for an hour or two together out of their 

 burrows, fully exposed to the morning light, but it appears, 

 from what some writers have said, that a light will occasion- 

 ally cause paired individuals to separate. When a worm is 

 suddenly illuminated and dashes into its burrow, one is led 

 to look at the action as a reflex one, the irritation of the 

 cerebral ganglia apparently causing certain muscles to con- 

 tract in an inevitable manner, without the exercise of the 

 will or consciousness of the animal, as though it was an 

 automaton. But the different effect which a light produces 



