<434 PHILOSOPHICAL TRANSACTIONS. [aNNO ISQO-I. 



hours, its pulse is visible, and all the other parts more distinct, which cannot 

 be discerned by the naked eye before the beginning of the 5th day ; from 

 whence it seems very probable, that even the so early discovery of those parts 

 of the foetus by the microscope is not the discerning of parts newly formed, 

 but only more dilated and extended by the receiving of nutriment from the colli- 

 quamentum ; so that they seem all to have been actually existent before the in- 

 cubation of the hen. 



But the 2d thing which later discoveries have made probable is, that these 

 animalcules are originally in semine marium, et non in foeminis. And this I 

 collect from these considerations. 1. That there are innumerable animalcula 

 discovered in semine masculo omnium animalium. Mr. Lewenhoeck has made 

 this so evident by so many observations, that I do not in the least question the 

 truth of the thing. The reason of their multitude, and some of the difficulties 

 which thence arise, he has cleared to very good purpose, so that I shall not re- 

 peat them. 2. The observing the rudiments of the foetus in eggs, which have 

 been fecundated by the male, and the seeing no such thing in those which are 

 not fecundated, as appears from Malpighi's observations, make it very probable 

 that these rudiments proceed originally from the male, and not from the female. 

 3. The resemblance between the rudiments of the foetus in ovo, both before 

 and after incubation, and the animalcule, makes it very probable that they are 

 one and the same. The same shape and figure which Mr. Leuwenhoeck gives 

 of the animalcule, Malpighi likewise gives of the rudiments of the foetus, both 

 before and after incubation, and even the foetuses of animals appear so at first 

 to the naked eye, that Dr. Harvey acknowledges that all animals, even the 

 most perfect, are produced from a worm. 4. This gives a rational account of 

 many foetuses at one birth, especially that of the Countess of Holland ; and 

 how at least a whole cluster of eggs in a hen are fecundated by one coition of 

 the male. 5. The analogy between the manner of the propagation of plants 

 and animals likewise makes this probable. Every herb and tree bears its seed 

 after its kind, which seed is nothing else but a little plant of the same kind, 

 which being thrown into the earth, as into its uterus, spreads forth its roots, 

 and receives its nourishment; but has its form within itself; and we may 

 rationally conjecture some such analogy in the propagation of animals. 



The 3d particular which later discoveries make probable, is that animals can- 

 not be formed of these animalcules without the ova in females, which are 

 necessary for supplying them with proper nutriment : and this is evinced from 

 these considerations, 1. It is probable, that an animalcule cannot come for- 

 ward, if it do not fall into a proper nidus. This we see is the cicatricula in eggs, 

 and though a million of them sl)ould fall into an egg, none of them would come 



