7 8 THE POPULAR SCIENCE MONTHLY. 



did not save them. There never yet was armor "without vulner- 

 able point. Nature "arms and equips an organism to find its 

 place and living in the world, and at the same time she arms and 

 equips another to destroy it." Squirrels deftly open the hardest 

 hickory nuts ; larvte penetrate the thickest-shelled almonds. 

 Wallace describes how cleverly the black cockatoo of the Aru 

 Islands breaks into the kanary nut, which is so hard that only a 

 heavy hammer will crack it. 



Every little helps, and the absence of the straw may save the 

 camel. Therefore, if in addition to their hard coverings these 

 fruits are also colored so as not to be easily seen, they have still 

 another advantage. Mr. Bailey describes the pods of the sensitive 

 pea as "protectively imitative," much resembling the leaves of 

 the same plant when closed after irritation. Wallace thinks that 

 the dry fruits of herbs " have no doubt often been prevented from 

 acquiring bright colors by natural selection, in order to protect 

 their seeds." And it seems logical that the same purpose may be 

 served by the sober colors of the larger dry fruits. 



Fuller describes a kind of figwort as a possible instance of a 

 protectively colored floiver. The blossoms are inconspicuous and 

 purplish; the ripening ovary develops a dark purple tint, and 

 somewhat resembles the fallen corolla; the buds, too, are as 

 deeply colored as the opened blossoms, an unusual thing. Since 

 this species is adapted to pollination by wasps, and avoided by 

 other insects which have a respectful awe of their formidable 

 sting, the miniature flowers and the fruits seem to be well pro- 

 tected by resembling the blossoms — an economical method to say 

 the least, and so effective that the wasps themselves, sometimes 

 deceived, were seen to alight on the buds and ovaries. 



III. Warning Color. — In the forests of Nicaragua there is a 

 brilliant red and blue frog, which is scornfully rejected by the 

 birds who usually devour frogs and lizards greedily. All the 

 other batrachians are protectively colored and feed only at night ; 

 but these little fellows hop boldly around with no thought of 

 fear. A certain hermit crab is found always in shells which are 

 covered with a (usually) bright-colored sponge or sea-anemone, 

 both of which are avoided by the crab's enemies. In such cases 

 striking color is correlated with obnoxious chemical qualities, 

 and the enemies understand it. 



It would be decidedly advantageous to plants which are not 

 otherwise fitted to survive the attacks of herbivorous animals to 

 accumulate substances offensive to them and then to advertise 

 their disagreeable qualities as clearly as possible, either by pecul- 

 iar form or color or odor ; and what we are constantly learning 

 of the sagacity of animals leaves little room for doubt that they 

 would quickly recognize these species and shun them. 



