214 EMBRYOLOGY IN THE SEVENTEENTH [pt. ii 



fluence in the biological world at the time, so that Wolff's conceptions 

 did not immediately yield fruit in any general advance. Looking 

 back over the second half of the seventeenth and the first two-thirds 

 of the eighteenth century, it is remarkable how little theoretical 

 progress was made in view of the abundance of new facts which were 

 discovered. Punnett, in an interesting paper, has vividly brought this 

 out. "The controversy between the Ovists and Animalculists had 

 lasted just a century", he says, "and it is not uninteresting to reflect 

 that the general attitude of science towards the problem of generation 

 was in 1775 niuch what it had been in 1675. When the period opened, 

 almost all students of biology and medicine were Preformationists 

 and Ovists; at its close they were for the most part Ovists and Pre- 

 formationists." Ovism sprang in the first instance from de Graaf's 

 discovery of the mammalian egg, which gave a new and precise 

 meaning to Harvey's aphorism. Preformationism, already old as a 

 theory, acquired an apparent factual basis in the work of Malpighi 

 and Swammerdam, and allied itself naturally with ovism. With 

 Leeuwenhoek and his spermatozoa, animalculism came upon the 

 field. The main outlines of the battle which went on between the 

 two viewpoints have already been drawn, but it is worth remembering 

 that there were independent minds who were impressed by the obvious 

 facts of heredity and found it difficult to call one sex essential rather 

 than the other. Among these Needham and Maupertuis might be 

 counted, and among the lesser men, James Handley with his Me- 

 chanical Essays on the Animal Oeconomy of 1730 ought to receive a 

 mention. Though fond of theological arguments he upheld the 

 common-sense attitude against ovists and animalculists alike — "We 

 dissent in some things", he said, "both from Leeuwenhoeck and 

 Harvey. . . . Both the semen and ova (notwithstanding all that can 

 be said) we believe to be a causa sine qua non in every Generation". 

 But what finally killed animalculism was the discovery in so many 

 places of small motile living beings, flagellates, protozoa, large 

 vibrios. It was difficult to maintain in the face of this new evidence 

 that the spermatozoa were essential elements in generation, though 

 the seminal fluid itself might very well be, as of course was Spallan- 

 zani's opinion. The preformation theory was what was holding up 

 further progress, and when Wolff's arguments prevailed in the very 

 last years of the eighteenth century, the way was open for the 

 recognition of the true value of the spermatozoa. 



