SECOND LECTURE. J25 



On the whole, there is every reason to believe 

 that the origin of all animals has been the same, 

 and that the laws and conditions which prevail in 

 the economy of other animals, take place also in 

 the reproduction of insects and worms; the only di- 

 versity in "elation to these animals is, that in these 

 classes of ler productions, nature accomplishes her 

 purposes by some peculiarities of structure, and 

 mode of action. I submitted this note to the criti- 

 cism of a friend, who favoured me with the fol- 

 lowing observations. 



^^The doctrine of equivocal generation arose first^ 

 I believe, from a want of accurate observation ; for 

 the Epicureans were not nice observers. It has 

 since been supported by ignorance and pride which 

 are commonly associates. 



This subject is very well treated in the 7th 

 book of Cardinal Polignac's Antilucretius. Some 

 writers on intestinal vermes seem not to be aware 

 that it is necessary carefully to distinguish insects 

 from worms, as they belong to different classes of 

 animals. The former, it is well known, are pro- 

 duced from eggs vivified by the male influence. 

 In some of these the larvae are excluded witliin 

 the body of the parent, others after the eggs are 

 deposited, and in one genus both these modes oc- 

 cur. If you have an Encyclopaedia at hand (which 

 1 have not) read the article Aphis. Many of the 

 vermes, we know, are produced from eggs. I 

 have often found those of the common eartli worm. 



