THE SEQUOIA 



the chick, laid the foundations of the study of embryology, one 

 of the four great supports of the theory of evolution; and pro- 

 pounded the theory of E pi gene sis, a theory vigorously argued by 

 philosophers for many years. The compound microscope, al- 

 ready mentioned, was applied to the study of organisms by Leeu- 

 wenhoek and Malpighi. The former demonstrated capillary 

 circulation (1690) and discovered red blood corpuscles, infusioria 

 and spermatozoa (1677). These spermatozoa were regarded by 

 some as parasites of animal bodies, by others as embryos which 

 only needed nourishment to develop into an adult form. Mal- 

 pighi applied the microscope to the study of the chick, and his 

 observations led him to announce the theory of Preformation, 

 which was opposed to the epigenesis of Harvey. 



The preformationists contended that a given species con- 

 tained within its sperm or ovum all the descendants of that 

 species, with all organs and parts fully formed. In other words, 

 embryos were only miniature adults, and were contained one 

 within another like a series of Chinese boxes, in successive grades 

 of size. The doctrine of epigenesis was that each sperm or ovum 

 contained a homogeneous living substance which became differ- 

 entiated by gradual changes into an individual resembling the 

 parent. Preformation was supported by Spallanzani, Bonnet, 

 Haller and even Cuvier. Its absurdity was shown by the work 

 of Wolfe (1759), who firmly established the doctrine of epigene- 

 sis as it is believed to-day, although more frequently known as 

 embryological development. 



The stimulus given to research by Harvey's discovery, the 

 intercourse and exchange of views among men, and the voyages 

 to all parts of the world resulted in an accumulation of a great 

 mass of facts, which were of little value unless classified. Conrad 

 Gesner (in 1551-1558) had given a complete bibliography of 

 zoology, and was the most important of the earlier naturalists. 

 About a hundred years later Ray, an English zoologist (1670), 

 made an attempt to establish a " system of classification," but he 

 had no true conception of species. It remained for Linnaeus to 

 complete a system which served its purpose so well that it has 

 remained practically unchanged to the present time. 



