LETTER XVII. 



To the same. 



i8/b, 1768. 



EAR SIR, On Wednesday last arrived your 

 agreeable letter of June the loth. It gives 

 me great satisfaction to find that you pursue 

 these studies still with such vigour, and are 

 in such forwardness with regard to reptiles 

 and fishes. 



The reptiles, few as they are, I am not 

 acquainted with, so well as I could wish, with regard to 

 their natural history. There is a degree of dubiousness and 

 obscurity attending the propagation of this class of animals, 

 something analogous to that of the cryptogamia in the sexual 

 system of plants : and the case is the same with regard to 

 some of the fishes ; as the eel, &c. 



The method in which toads procreate and bring forth 



