I 4 2 SCIENTIFIC ILLUSTRATIONS [Kal 



cases with mankind in the inheritance of tricks or unusual 

 gestures. As to the domination which evil habit acquires over 

 men, that needs not even a passing allusion. It is remarkable 

 that the force of habit may affect even caterpillars. Caterpillars 

 which have been fed on the leaves of one kind of tree have 

 been known to perish from hunger rather than to eat the leaves 

 of another tree, although this afforded them their proper food 

 under a state of nature. Their conduct might suggest reflec- 

 tion to men who are tempted by habit to risk death by adher- 

 ence to debauched courses rather than return to a natural mode 

 of living. EX. 



Age Altering Habit. 



A few years often change the habits of a man. The middle- 

 aged man has scarcely any of the habits of the youth left. 

 And if the proof of his identity depended on their resemblance, 

 it would indeed be hard to establish. A like change of habit 

 is observable in many other existences. We may take from a 

 class of molluscs the acorn shells (Balanus balanoides) as an 

 example. It is a very remarkable fa^it, that although the 

 balanus never moves from the spot on which it has taken up 

 its habitation, and, indeed, is incapable of any kind of locomo- 

 tion, yet when very young it was an active, wandering little 

 creature, furnished with jointed limbs, much resembling a 

 shrimp or crab, and swimming freely through the water with a 

 succession of bounds. "What a complete settling down to quiet 

 ways ! what a thorough transformation is here ! But is it 

 more striking than the metamorphosis of the hobbledehoy 

 youngster into the sedate sage ? D. 



Half-Truths and Hemiopia. 



There is an affection called hemiopia, in which the patient 

 can only discern a part or the half of an object. He may see 

 a man walking without head and shoulders ; or with the upper 

 portion of his frame hovering in the air, but no lower limbs to 

 sustain it ; or with a trunk like a mutilated statue j or with a 

 body which has only a single eye, half a nose, half a chin 

 appearing, in fact, to be sliced down the centre, as if the one 



