xxiv INTRODUCTORY OBSERVATIONS. 



cafes, it mud be acknowledged, that the 

 boundlefs empire of nature has neither been com- 

 pletely explored, nor reduced v/ithin determinate 

 limits by human underftanding, and perhaps 

 never will. 



Seminal vermiculi are a race of animals 

 whofe origin, exifkence, and ufe, if they are of 

 any, are all equally myflerious. Their origin 

 is even more wonderful than that of the numerous 

 other worms inhabiting the bodies by which they 

 are nourifhed. Every thing contributes to the 

 difficulty of inveftigating their nature. The ter- 

 mination of life, or the cruel mutilations that 

 mufl be employed to view them in their native 

 abode ; the ravages and diforder that fuch ope- 

 rations muft occafion ; and their extreme mi- 

 nutenefs (for it has been computed that the dia- 

 meter of fome does not exceed one hundredth 

 part of the thicknefs of a human hair) render it 

 furprifmg how fo much of their hiftory has been 

 difcovered. But the period is yet diftant, when 

 every kind of propagation fhall be known. Two 

 thoufand years ago, the generation of eels occu- 

 pied the attention of naturalifts, and it is flill ob- 

 fcure. — The chief difficulty which attends our 

 comprehending the origin of feminal vermiculi is 

 their appearance only at a certain age. Where do. 

 ;hey exift before this term arrives ? The germ or 



primordiu,m 



