232 The Microscope. 



tender; the best way of holding them for examination by the mi- 

 croscope, is by the wings, in the spring forceps. When they are 

 in the larva state, a watch-glass half filled with water is the most 

 convenient; the smallest species are best adapted for this purpose, 

 as being the most transparent; they have seven paddles on each 

 side. 



Luminous Water Insects. The Rev. Mr. Baker, in his 

 observations on luminous insects in water, says that he has been 

 surprised sometimes at the sparks of hght to be seen on the shells of 

 oysters, on removing them, when fresh taken from the sea. He 

 bestowed some pains to find out the cause, and was perfectly Con- 

 vinced, after many examinations, that it arises from a minute in- 

 sect, the length of which is about one eighth of an inch: the head 

 is armed with a pair of forceps; the body consists of twenty-eight 

 joints or divisions, each having a pair of feet belonging to it. 

 This little insect can emit or conceal its light, and is very similar 

 to the glow-worm. 



Sea-water. Another account is given by Dr. Veanella, of 

 Chioggea, in .Italy. In his inquiry into the shining of sea-water 

 in the night, which he says is seen with wonder in the lakes of 

 Chioggea, where sea-weeds abound, he relates that he brought 

 from thence, one summer's night, a bottle of the water, which, be- 

 ing stirred in the dark, sparkled; but, after being filtered through 

 a cloth, afforded no light at all, while the cloth was covered with 

 shining particles, which, being examined by the microscope, were 

 discovered to be living insects, formed something like a caterpillar, 

 with ringlets on the body; from the head issued two horns, and the 

 tail appeared twisted. These insects are entirely luminous, and 

 when at rest do not shine at all, but send forth a great hght as soon 

 as they become agitated. 



Vorticella, orAVheel Insect. This surprising insect is 

 found in leaden gutters, not exceeding the size of a grain of sand; 

 you may often discover it in ponds, ditches, upon duck-weed, ^'c, 

 and in water that has stood sometime in vessels in the house, adher- 

 ing to the sides, and in the infusion of hay: if the- v^^ater or the 

 sediment in gutters has a red appearance, you will most likely find 

 some: the minuteness of these insects makes it impossible to 

 know whether you have them or not without examination with the 

 glasses. The best way of discovering them is by placing some 

 of the sediment under the low power of the microscope. If you 

 find any there, then screw on a higher power, and watch their mo- 

 tions with attention. This little creature shows itself first like a 

 transparent maggot, lengthening out its body at times, and at oth- 

 ers contracting it, — changing again its form in an instant, as figs. 



