LAMARCK 85 



adults are beautifully and conspicuously colored, and their bodies 

 are often drawn out into long spines and processes. In the zoea 

 of Porcellana, for example, these spines are so long, as compared 

 with the body proper, that this zoea when seen with a lens reminds 

 one of an oarsman seated in the middle of a very long, sharp-pointed 

 glass boat. Often the spines are strengthened by calcareous ladders 

 formed of long parallel transparent side-strips, like glass threads, 

 with cross-bars at regular intervals. No one who has strained his 

 eyes to discover in a glass of water one of these transparent 

 larvae which he has captured, and, after repeated attempts to suck 

 it into a dipping-tube for study under the microscope, fails, because, 

 even when the end of the tube is at last brought directly over it, 

 it catches across the end of the tube and permits the current of 

 water to rush by without drawing it in, can doubt that the transpar- 

 ency of pelagic larvae is protective, or that the spines and processes 

 keep them out of the mouths of their enemies, just as a long 

 ladder may keep the man who carries it from slipping through holes 

 in treacherous ice. 



The way the spines of a zoea, or the ladders of a pluteus, increase 

 what may, figuratively, be called the angle of incidence, is so clear 

 that few students of marine zoology will hesitate to make still farther 

 use of the language of the mathematicians, and to assert that the 

 number of mouths large enough to swallow a pluteus decreases 

 inversely as the square of the angle of incidence. 



A naturalist was stopped, in the jungle of Java, by a dense bush, 

 on a leaf of which he saw a butterfly sitting on what he took to be 

 a bird's dropping, and, as he had often wondered at this habit, he 

 approached with gentle steps and ready net, to see, if possible, how 

 the insect was engaged. It permitted him to get quite close and 

 even to seize it with his fingers, but he tells us that to his delighted 

 surprise part of the body remained behind, adhering, as he thought, 

 to the excreta ; but looking more closely, and finally touching it 

 with his finger, he found, to his astonishment, that his eyes had 

 been most perfectly deceived, and that what seemed to be the ex- 

 creta was a most artfully colored spider, lying on its back with its 

 feet crossed over and closely pressed to its body, thus producing a 

 living bait for butterflies and other insects so artfully contrived as 

 to deceive a pair of human eyes, even when intently examining it. 



