104 INSTINCT 



ceans is the peculiar trait shown by several species of spider 

 crabs of decking themselves out with a covering of seaweed, 

 sponges, hydroids, etc., so that they are quite effectually 

 concealed in their natural surroundings. Spider crabs 

 kept in aquaria have been seen by several observers to snip 

 off bits of seaweed with their pincers, reach over their backs 

 and stick them down among the stiff curved hairs which 

 occur on the upper surface of the carapace. The seaweeds 

 and sessile animals thus transplanted often grow, so that 

 the back of the crab comes to be a veritable botanical and 

 zoological garden on a small scale. There are few instinc- 

 tive acts which appear to be more the result of deliberate 

 intention, yet the disguisement is not only instinctive, but, 

 as Minkiewicz has shown, it is performed by crabs in which 

 the brain is entirely cut off from connection with the legs by 

 cutting the esophageal commissures that lead to the large 

 ventral ganglion. The sense of wonder with which instinct 

 was formerly regarded, and which the reflex theory might 

 seem to rudely destroy, is a sentiment which can scarcely 

 fail to arise when we contemplate the organization which 

 makes possible the blind performance of such remarkable acts. 

 Among the bisects, as hi the Crustacea, the seat of many 

 instincts is in the ventral ganglia rather than in the brain. 

 A decapitated fly is able to walk and fly and go through with 

 elaborate movements of cleaning the wings, legs and body. 

 In experiments made by the writer on the water scorpion, 

 Ranatra, it was found that after decapitation the insects 

 were able to walk and swim almost as well as before. In 

 fact, they became much more restless and would walk about 

 for hours without 'coming to rest; and when they finally 

 became quiet they could be aroused by the slightest stimuli. 

 When placed on their backs they would readily right them- 

 selves. If the tip of the breathing tube was seized while the 



