MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 125 



germanica) of its eyes, observed that it Could still perceive light. Plateau and E. Van Beneden 

 have also made observations on Niphargus puteanus, whose incompletely developed eyes are 

 wanting in pigment. Plateau's experiments were made on species of Geophilus and Cryptops 

 found living uuder heaps of refuse. He appears to have proved — 



1. That they perceived daylight and could choose between this light and darkness. 



2. Both in Chilopoda with eyes and in Chilopods without them quite a long time is needed 

 before these animals can perceive that they have passed from a relative or complete obscurity to 

 daylight. 



3. The length of this latent period is not greater in blind Myriopods than in those with eyes. 



4. When either blind or eyed Myriopods placed on the ground run quickly into the first 

 opening they find, this act is not simply to escape light; these animals also seek for a humid medium 

 with which the greater part of the surface of their bodies may be in direct contact. 



These experiments and conclusions are of great interest in connection with cave Arthropods, 

 since it appears to show that total darkness with humidity are perhaps not so adverse to inverte- 

 brate life as would at first sight seem, and that perhaps the limited source of the food supply is 

 an equally important factor in cave life. The loss of eye-sight, however, would seem to be amply 

 made up to these beings by the senses of smell and touch. 



Deprived of their eyes, cave animals in general are much more wary and guarded in their 

 actions than their allies which enjoy good eyesight. This point is well illustrated by Prof. F. W. 

 Putnam's observations on the habits of the blind crayfish (G. pellucidm) from Mammoth Cave.* 

 When food was offered to G. bartonii and to C. pellucidus, the difference in the action of the two 

 species was striking, as showing the timidity and exceeding caution of the blind form. The C. 

 bartonii seized the piece of meat or bread and hastily ate it, without showing any fear of its 

 keeper. " The blind species, on the contrary, darts backward as soon as the food is dropped into 

 the water and then extends its antennae and stands as if on the alert for danger. After a long 

 while, sometimes from fifteen to thirty minutes, it will cautiously crawl about the jar with its 

 antennse extended as if using them for the purpose of detecting danger ahead. On approaching 

 the piece of meat, and before touching it, the animal gives a powerful backward jump and remains 

 quiet for awhile. It then cautiously approaches again, and sometimes will go through this per- 

 formance three or four times before it concludes to touch the article, and when it does touch it, 

 the result is another backward jump. After another quiet time it again approaches, perhaps only 

 to jump back once more, but when it finally concludes that it is safe to continue in the vicinity of 

 the meat, it feels with its antennae for awhile and then takes the morsel in its claws and conveys 

 it to its mouth." 



Regarding the sensibility to light of the blind Crustacea, the following notes are of interest; 

 Mr. Putnam kept a (J ambar us pellucidus from Mammoth Cave about ten months "exposed to the 

 full light of day." He also states that " extremes of temperature do not affect these crawfish 

 from the cave, as my several specimens have been a number of times retained for days in a heated 

 room, and again have been exposed for weeks to such intense cold as to freeze the water in their 

 jars." Crayfish possess unusual vitality, as is proved by the great number of species and 

 individuals of the epigean members of the family ; but the smaller blind Crustacea show great 

 sensibility to light. Bate and Westwood state that Mphargus puteanus "perish in the light." 



Compensation by increased olfactory powers. — It seems probable that the sense of smell is 

 keener in animals which have lost their eye-sight. It is well known that the dog is more dependent 

 on his remarkably keen scent'than on his eyes in tracking game and the footsteps of his master,* 

 while in insects the olfactory sense is exalted. 



The first author, so far as we have been able to ascertain, to describe and figure the olfac 

 tory rods of the blind Amphipods and Isopods, and to show that they have a greater development 

 than in the species with normal vision, was De Rougemont, in 1876. He agrees with Leydig, that 

 the rods in question are olfactory; and, as will be seen by the following extract, he claims that 



* Proc. Boat. Soc. Nat. Hist., xviii, 16. 



+ Aiusi le chien de chasse trouve la piste d'un lievre au lnoyen de l'odorat, et suivant cette piste il arrive im- 

 manquablenient au glte du lievre; si celui-ci part avant que lo chien l'ait saisi, le chien le voyant le poursuivra non 

 pins an moyen de l'odorat, mais an inoyeu de la vue (De Kougemout, Etude, etc., 13). 



