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 Epigeneszs, 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 zodlogist (1670), 
made an attempt to establish a “‘system of classification,” but he 
had no true conception of species. It remained for Linnzeus to 
complete a system which served its purpose so well that it has 
remained practically unchanged to the present time. 
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