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LETTER XX. 



ON THE REPRODUCTIVE FUNCTIONS OF THE MOLLUSCA. 



THE doctrine which taught us that insects and worms 

 were the offspring of mud and slime, or the natural pro- 

 ducts of the corruption and fermentation of animal and 

 vegetable matter, was applied with equal confidence to 

 explain the origin and propagation of oysters, slugs, and 

 snails ; * and even after the true theory, that every living 

 thing proceeds from a parent like itself, had been estab- 

 lished apparently by the numerous experiments of Redi, 

 and by the progress of a rational physiology, there were 

 not wanting some advocates of the wisdom of foregone 

 times who continued to entertain the elder hypothesis. 

 Father Philippo Buonanni, a learned Jesuit, was one of 

 these. In his " Recreation of the Eye and Mind," pub- 

 lished in 1681, "it being a pretty large volume containing 

 the natural history of all the snail kind," after an attempt 

 to throw suspicion over the experiments of Redi, he de- 

 clares his belief " of their being equivocally produced out 

 of putrefaction," for which, says his candid critic, " he brings 

 little proof besides the well-known reasons and authority 

 of Aristotle." And this authority was so great, and vulgar 

 prejudice so strong in its favour, and observation on these 

 creatures so little advanced, that when an anonymous author, 

 of whose work there is a short account in the Philosophical 

 Transactions for 1603, opposed the Italian Jesuit, not with 

 argument but with a simple observation, having seen the 

 young snails issue from their eggs which he had found in 

 his garden, he was afraid to give publicity to the fact with- 

 out the evidence of witnesses. " This discovery being very 

 plain and remarkable, he called in to see it many learned 

 persons, and some of good quality, whom he names, that 

 the truth of his asseveration may be out of dispute." Be- 

 yond dispute it is now, and has long been, for although 

 some recent attempts have been made to revive the ancient 



* The reader who wishes to see how this opinion was argued may refer 

 to Rondeletius de Piscibus. " De Piscibus sponte naseentibus." Lib. iv. 

 c. iv. ; or Hist, des Poissons, p. 83. 



