TOL. XVII.] PHILOSOPHICAL TRANSACTIONS. 431 



On the Modern Theory of Generation, by Dr. George Garden, of Aberdeen. 



N" 192, p. 474. 



You know how unconclusive men's conjectures were on this head until this 

 age, when Dr. Harvey discovered tiie proper place of the formation of the chick 

 in the cicatricula of the egg, and the formation of the parts, so far as was dis- 

 cernible by the naked eye ; and after him Malpighi, by the help of exact glasses, 

 observed the first rudiments of it there, both before and after incubation : and 

 R. de Graaf and others, having upon many observations concluded, that the 

 testes foeminei were the ovaries of females, and consequently that all animals 

 were ex ovo ; they began from hence to infer, that the rudiments of each ani- 

 mal were originally in the respective females, and that the male contributed 

 only to give a new ferment to the mass of the blood and spirits, by which means 

 a spirituous liquor (which the blood in its ordinary ferment could not produce) 

 insinuated itself to the same ducts and pores of the rudiments of those animals 

 which were in greatest forwardness in the ovary, and so extended and enlarged 

 all their parts, and at last brought them to perfection, as M. Perrault ingeni- 

 ously discourses in the 3d part of his Essais de Physique ; till now at last 

 Leuwenhoeck has discovered an infinite number of animalcula in semine marium 

 of all kinds, which has made him condemn the former opinions about the pro- 

 pagation of all animals ex ovo. 



Now upon comparing the observations and discoveries which have been made 

 with each other ; these three things seem to me very probable. 1 . That ani- 

 mals are ex animalculo. 2. That these animalcules are originally in semine 

 marium, et non in foeminis. 3. That they can never come forward, nor be 

 formed into animals of the respective kind, without the ova in foeminis. 



The first of these seems probable from these three observations, l. That 

 some such thing has been so often observed by Malpighi in the cicatricula of 

 an egg before incubation, as the rudiments of an animal in the shape of a 

 tadpole, as may be seen in his first, and in his repeated observations de forma- 

 tione pulli in ovo. 2. The sudden appearance and displaying of ail the parts 

 after incubation makes it probable, that they are not then actually formed out 

 of a fluid, but that the stamina of them have been formerly there existent, and 

 are now expanded.' The first part of the chick which is discovered with the 

 naked eye, is the punctum saliens, and that not till 3 days and nights of incu- 

 bation be past, and then on the 5th day the rudiments of the head and body 

 appear. After an incubation of 30 hours, are visible by glasses the head, the 

 eyes, and the carina, with the vertebrae, distinct, and the heart. After 40 



