lyo THE HISTORY OF BIOLOGY 



were at that time lumped together, and Swammerdam's point of departure 

 was from first to last not morphological, but evolutionary. But at any rate 

 he performed a service — as also did Leeuv/enhoek — in awakening interest 

 in these organisms, which had hitherto been regarded as existences not only 

 of a lower type, but also utterly incomparable with the higher; they still 

 arose, according to Harvey, by spontaneous generation, and this alone was 

 a proof that no conclusions could be drawn from them touching the life of 

 the higher animals. 



Sivammerdam s pejormation theory 

 SwAMMERDAM showcd that on the contrary it was just the life-conditions 

 of the lower animals which, if viewed in a proper light, gave fresh stimulus 

 to the knowledge of life in its entirety. Particularly does he insist upon 

 this being realized in embryonic development. The theory which he ad- 

 vanced on this subject — growth of previously created parts instead of new 

 formation — came to exercise immense influence during the immediately 

 succeeding period: under the name of the theory of preformation or evolution 

 it entirely supplanted Harvey's theory of epigenesis. True, in its application 

 it was in its turn driven to sheer absurdities, particularly by certain scientists 

 who will be named later on, but when it first appeared, it was certainly 

 called for and marked an advance in biological science. In fact, it resulted 

 in the assertion for the first time of the obedience of ontogenetical evolution 

 to law; it definitely invalidated the old ideas of the spontaneous genesis 

 of lower animals; it established the fact that according to nature the off- 

 spring must resemble the parent, whereas in earlier times, practically speak- 

 ing, anything could arise out of anything — the legendary tales of women 

 who under the influence of witchcraft were delivered of kittens and puppies 

 instead of children had at any rate been discussed by certain scientists — 

 and, finally, it satisfied, as far as embryology was concerned, the contem- 

 porary demand for a mechanical explanation of nature. But it is true that a 

 century later the epigenetical theory was again to appear in a form that jus- 

 tified its acceptance — a change of which an account will be given further on. 

 There is a name that is worthy of mention by the side of Swammerdam 

 — that of his contemporary and friend Frederic Ruysch. He was born at 

 The Hague in 1638 of a highly respected family, his father being secretary 

 in the States General. Having when still young contracted an advantageous 

 marriage, he was in a position to apply himself at his own option to medical 

 research; he became a doctor at Leyden and a professor in Amsterdam, in 

 an appointment which he held for sixty-three years. Moreover, he had an 

 extensive medical practice. He died in 173 1 in his ninety-third year. His 

 long life, active to the last, is reminiscent of Leeuwenhoek's, as is also the 

 fact that his greatest service to the world consists in the employment of 

 technical methods, which, though he had not invented them, were neverthe- 



