animalcular tribe, the higheft degree of contractile 

 power ; in confequence of which it occafionally appears 

 in all the various dates of elongation and contraction 

 reprefented in the plate ; and not unfrequently reduces 

 itfelf to a globular form. Its motions are rather How 

 than fwift, and when fwimming at full length it gene- 

 rally appears tranf; arent' at both extremities, while the 

 body feems filled with a congeries of globules or grains 

 of a green or reddifh colour, and not ill refem- 

 bling the fpawn of fiflb. The head or fore-part is ob- 

 tufe, but the tail or extremity is acute, and fometimes 

 exhibits a flight appearance of bifurcation at the tip ; 

 but this is a particular which in general is fcarce to be 

 perceived. The difference in colour between thefe 

 animalcules feems hardly fufficient to juftify our regard- 

 ing them as fpecifically diftindt ; fince both the green 

 and the red fort are fo perfectly alike in other refpe&s 

 that no difference can be perceived between them. 

 The green fort may be very frequently obferved in 

 moft ftagnant waters in the months of May and June, 

 and fometimes much fooner, appearing commonly on 

 the furface in the evening and early in the morning, 

 and retiring towards the middle of the clay to the bot- 

 tom. The red variety is far lefs common, and the 

 appearance which it fometimes exhibits is fuch as to 

 alarm a fuperftitious mind with the idea of the water 

 being tinged with blood : a panic of which numerous 

 inftances have been adduced by authors ; and which is 

 the more excufeable in thofe who are ignorant of the 

 caufe, as the animalcules are fo extremely minute as 

 to be utterly imperceptible, (except to an uncommonly 



fharp 



