Sf6 PHILOSOPHICAL TRANSACTIONS. [aNNO 1/03. 



ceous and testaceous. Fig. 1 7* and 18 show them as they swim with their back 

 upwards ; but the members and legs on the other side are so various, and so 

 much more curiously formed, than those of lobsters and shrimps, that I de- 

 spaired of giving any tolerable representation of them in any other position. 

 These are about the same size, the largest being rather less than a very small 

 flea, and the least a little larger than a mite ; but all are breeders, and carry 

 their spawn at their tails ; that represented fig. 18, in two bags, one on each 

 side, which are fastened about the 5th joint ; and the other in a single bag or 

 film under the tail ; and I have often seen these bags broken, and the spawn, 

 which is globular, and large in the proportion to the fish, scattered through the 

 water. There is also among these a third sort of the same kind, not less elegant, 

 though far less in bulk, which is shaped more like a shrimp, and carries its 

 spawn like that. All these three species, as also some other water insects, are 

 certainly monoculous, and have their eye exactly in the middle of their head ; 

 and I could never, with my utmost attention, find so much as a dividing line in 

 it. Some of them, especially in some waters, are dark and cloudy ; but gene- 

 rally they are so transparent, that through the shell I can see the peristaltic 

 motion quite through their whole length, and a constant pulsation of a part, 

 which I guess is the heart ; but I could never discover any course of blood in 

 them (nor even in shrimps themselves which are as large as some thousands of 

 these) though I have seen it plainly in animals a little larger, viz. the smallest 

 new hatched spiders, and in that water insect which is described and figured, 

 though not accurately, by Swammerdam, under the improper name of pulex 

 aquaticus. But this is of the testaceous kind, of which I have seen a greater 

 variety, and not less curious than those of the crustaceous. 



I have further observed the lens palustris, and am fully satisfied of the truth 

 of its first springing from the bottom. I lately took up some on the shallow 

 side of a pond, and found the ends of the stalks (most of which were at least 

 5 inches long, and as thick as a strong horse hair) manifestly rooted in the 

 bottom ; so that I could not take them up without raising the mud with them, 

 which also adhered very visibly to them. These stalks or roots are of a curious 

 texture, and almost transparent, and I have seen their outside very prettily co- 

 vered with a regular sort of net- work. Mr. L's figure represents them but 

 badly. 



In my observations of these stalks, I often saw adhering to them, and some- 

 times separate in the water, many pretty branches, composetl of rectangular 



* McMioculus quadricornis. Liniu 



