PREFACE. Ill 



fupply the place of other elucidations. But an 

 ample field will be found for many more than 

 are there. 



I muft acknowledge, that I have fometimes 

 been at a lofs to difcover the exaft fpecies of 

 feeds which the author ufed for infufions. He 

 feldom or never gives fpecific names ; and in 

 Scotland little is yet known of Italian botanical 

 fynonyms. However, it is of lefs importance, as 

 many different infufions will produce the fame 

 animalcula. In my ov/n obfervations on thefe 

 iingular animals, during feveral years, I believe I 

 have difcovered almofl the whole which have 

 been the fubject of the author's confideration. A 

 few I have not found, or have been unable to re- 

 cognife. 



It will eafily be perceived, thatthe Treatifes on 

 Animal Reproduction originally formed no part 

 of the Tracts. Therefore the reader may reafo^i- 

 ably inquire, why he finds them here.' — Such in- 

 veftigations may properly conflitute a fixth fub- 

 jeft, on which as great learning and ingenuity 

 are beflowed as on the reft. This is a fiudy which 

 feenis to have made Icfs progrefs in Britain than 

 on the Continent ; there are few or no original 

 .experiments in Engliih, and fome of the follow- 

 ing trads are difScuit to be procured : thereforr 



b 2 •■ 



