OATACLYSTA LEMNATA. 75 



a few minutes came out of the case as far as the fifth 

 segment, and by crawling soon managed to arrive at 

 the side of the glass, along which it continued to 

 crawl at the level margin of the water, occasionally 

 turning itself round within its case, and coming partly 

 out at the other end, thus proving the case to be open 

 at both ends — a fact which was not suggested by its 

 appearance. The external figure of the case was of 

 an irregular oval form, nearly half an inch in length, 

 and varying in width from two to three lines, the 

 leaves of which it was formed overlapping each other, 

 but in an irregular manner, and so contrived that a 

 leaf or two should bang down and mask the openings 

 at the ends, when the occupant, as was often the case, 

 remained quiet within; the two ends of the case are 

 not quite alike in their fashioning, and the whole 

 thing, when the larva is not seen, very much resembles 

 an accidental accumulation of some of the duckweed, 

 so slight is the eminence which it causes above the 

 general level of the surface. 



When the larva reposed just so far within its case 

 as only to show a little of its head, there was the 

 smallest conceivable silvery sparkle lurking at the 

 bases of its antennal papillae, and also about the 

 mouth ; but when it was in motion with two-thirds 

 of its body beyond its case, this quicksilver-like 

 appearance of air in water was exhibited more 

 extensively along each of its sides as a broad band, 

 and even the bases of its anterior legs were encircled 

 with radiance, and sparkling with each movement; 

 this luminous appearance changed its position with 

 that of the larva, according to the angle of light in 

 which it was viewed ; sometimes, behind the second 

 segment, the back appeared completely silvered over, 

 and sometimes the belly ; and at other times trans- 

 verse silvery lines marked the segmental divisions. 



After watching it some time I took it in my hand 

 and stripped off the case of duckweed leaf by leaf, 

 leaving the larva naked and perfectly dry ; then 



