SECT. 3] AND EIGHTEENTH CENTURIES 209 



Harvey, namely, as referring to the egg-shaped chorion of vivipara, 

 and definitely not in the sense of de Graaf and Stensen, namely, in 

 the modern sense. "Eggs", he says, "instead of being common to 

 all females, are only instruments employed by Nature for supplying 

 the place of uteri in those animals which are deprived of this organ. 

 Instead of being active and essential to the first impregnation, eggs 

 are only passive and accidental parts, destined for the nourishment 

 of the foetus already formed in a particular part of this matrix 

 by the mixture of the male and female semen." Biology at this period 

 was still labouring under the disadvantage of being without the cell- 

 theory, and therefore unable to distinguish between an egg and an 

 egg-cell. 



In spite of his leanings towards epigenesis, Buffon repeats precisely 

 the error of Malpighi. "I formerly detected", he says, "the errors 

 of those who maintained that the heart or the blood was first 

 formed. The whole is formed at the same time. We learn from actual 

 observation that the chicken exists in the egg before incubation. The 

 head, the backbone, and even the appendages which form the 

 placenta are all distinguishable. I have opened a great number of 

 eggs both before and after incubation and I am convinced from the 

 evidence of my own eyes that the whole chicken exists in the middle 

 of the cicatrice the moment the egg issues from the body of the hen. 

 The heat communicated to it by incubation expands the parts only. 

 But we have never been able to determine with certainty what parts 

 of the foetus are first fixed, at the moment of its formation." The 

 experiment of taking a look at the cicatrices of eggs on their way 

 down the parental oviduct is so obvious that Buffon must have thought 

 of it, and it would be really interesting to know what factor in the 

 intellectual climate it was that made him regard such an observation 

 as not worth attempting. His observations on the embryo itself were 

 good and, in some ways, new; thus he noticed that the blood first 

 appears on the "placenta" or blastoderm, and for the first few days 

 seems hardly to enter the body of the embryo. He gave an extremely 

 good account of the whole developmental process in the chick and 

 in man, and his opinions on the use of the amniotic liquid and the 

 functions of the umbilical cord were very advanced. 



J. T. Needham, however, spoke very clearly in favour of epi- 

 genesis, though he himself did no embryological experiments. His 

 Idee sommaire of 1776, written against Voltaire, who had called him 



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