654 



COLLEGE ZOOLOGY 



Anton) van Leeuwenhoek (Fig. 458) is 

 known as the father of protozoology. He was 

 born in Delft and at the age of 22 started 

 in business as a draper. He became inter- 

 ested in microscopes and ground his own 

 lenses. With his lenses he examined prac- 

 tically everything he could think of and 

 made many interesting discoveries. In 1674, 

 at the age of 42, he discovered free-living 

 protozoans in a fresh-water pond, includ- 

 ing what must have been Euglena and sev- 

 eral species of ciliates. The same year he 

 described parasitic protozoans, for the first 

 time, in material obtained from the gall 

 bladder of a rabbit. In 1681 he discovered 

 human protozoan parasites in his own feces 



Figure 458. Anton j van Leeuwenhoek (1632- 

 1723), the Dutch microscopist who discovered Pro- 

 tozoa. (Courtesy of Bausch & Lomb Optical Co., 

 Rochester, New York.) 



and described what one can recognize as the 

 intestinal flagellate Giardia. These and many 

 other discoveries were recorded, mostly in 

 the form of letters, to the Royal Society of 

 London. 



Leeuwenhoek's success was due to his 

 lively curiosity, keen powers of observation, 

 and his masterly skill in grinding lenses. He 

 left behind him 247 complete miscroscopes 

 and 172 mounted lenses. The best of these 

 magnified 270 to 300 diameters. Besides 

 free-living and parasitic protozoans, Leeu- 

 wenhoek discovered bacteria, rotifers, the 

 cross-striations of muscle fibers, the vivi- 

 parity of plant lice; and he described many 

 other animals and plants and their structures 

 and activities. 



Marcello Malpighi (1628-1694) was the 

 father of microscopic anatomy. Among the 

 specimens he examined were the embryos 

 of chicks, in which he recognized the begin- 

 nings of organs. This led him to the idea 

 that the adult is preformed in the egg. Em- 

 br}'ologists later discovered that the chick 

 really develops gradually. 



The electron microscope is one of the 

 newer magnifying instruments. It makes 

 magnifications up to 100,000 times possible. 

 In this microscope, a beam of electrons is 

 utilized, and the image may be recorded on 

 photographic film. 



Another development in microscopy is the 

 phase contrast microscope. In living cells, 

 some structures do not absorb visible light; 

 hence they are not visible under the ordinary 

 microscope. The phase microscope increases 

 the contrast of these structures by optical 

 means so that they may be observed. There- 

 fore, phase microscopy is invaluable for the 

 study of living cells. 



Carolus Linnaeus ( 1707-1778), a Swedish 

 scientist (Fig. 459), was the first great 

 taxonomist. Contrary to popular opinion, 

 Linnaeus did not originate our present sys- 

 tem of scientific nomenclature, but it was 

 formalized and universally applied by him. 

 Instead of giving animals common names 

 which might be used for different species in 



