EELS I N P A S T E. 535 



to the bottom j but cold does not hurt them. If frozen and thawed re- 

 peatedly, they repeatedly revive and become briik ; if a quantity of oil 

 be poured on the vinegar, they creep up into the oil when the vinegar 

 begins to freeze, and return to the vinegar when that is thawed. By a 

 few grains of fand put among them they are greatly embarralTed, and are 

 in a manner overwhelmed by fuch huge ftones. , 



Rain Water, after (landing a few days, exhibits fimilar appearances; 

 water in ditches and water that drains from dunghills is often fo crowded 

 with animals, as to feem all alive, efpecially the deep brown water from 

 dunghills. It is probable that fome of thefe animalcula are extremely 

 minute flies in their worm Hate, and undergo one transformation, if not 

 more, ere they become perfect ; others are unqueftionably in their 

 perfedl ftate, here breed, live, and die, without change. The infinite va- 

 riety of their forms, motions, parts, and contrivances for catching prey, 

 is unlimited. Some of them are congregated in millions of millions to 

 an inch fquare, under the appearance of mud, or weeds, or flime in 

 ditches : of all colours, efpecially blackifh-green. Some are like worms, 

 having membranous coverings ; other fhelled like mufiels, or cockles : 

 fome feem capable of varying their forms, feeming now rounded, now 

 lengthened, now with a long neck, now with quite a different conforma- 

 tion ; many of them refembie fuch infects as are familiar to us, and are 

 like them cruftaceous, have feelers, legs, tails, &c. Ufually the micro- 

 icopc fhews that their internal conformation is not altogether unlike, and 

 we conceive of them as having the fame parts in a general idea, but in- 

 expreffibly fmaller. Crabs and lobllers in form, and perhaps in manners 

 (fo far at lead as having fpawn under the tail, or in receptacles on each 

 fide of it), are common among them ; and it is not impoffible they alfo 

 change their flcins. 



In general thefe minute infedts may be referred to, (1.) Thofe which infeft 

 other animals, for there is no animal we know but has its plague of this 

 kind, as well fifh as beads and birds. (2.) Thofe infefting vegetables, 

 which are as numerous and different as vegetables themfelves. (3.) Thofe 

 found in frefh waters, rivers, drains, cuts, ditches, and (landing waters; 

 not a place without fome kind, which there inhabits and breeds; often 

 many various kinds, whofe forms befpeak utter dilfimilarity, (4.) Thofe 

 of the fea, whofe multitudes are too various to admit our knowledge. 



It requires no inconfiderable ftrength of thought and refleftion, no 

 inconfiderable mental exertion, to form any idea of this multiplied clafs 

 of beings : if we advert to thofe produced jn waters around us, of which. 



Part VI. No. 31. 3 Lr ' though 



