which he consequently referred to as the cytoblast. This point of view 

 seems to have been rather widely adopted and. despite some criticism, 

 it was not until the late 1840's that overwhelming evidence against this 

 concept and for the notion of cell formation by some form of replication 

 was put forth, primarily by Hugo von Mohl and K. Nageli. 



Long before Schleiden and Schwann advanced their ideas and obser- 

 vations on cellular structure, many workers had described or illustrated 

 cellular units. In 1665 Robert Hook introduced the term "cell" to de- 

 scribe the microscopic texture of cork, and in 1672 Nehemiah Grew 

 provided a number of illustrations of plant material which indicate that 

 he noticed the cellular structure. From 1674 over a considerable period 

 of years Anton van Leeuwenhoek, who is best remembered as a master 

 of the art of grinding short focal-length lenses, described many micro- 

 organisms, blood cells, and spermatozoa in amazing detail. That cellular 

 organization is characteristic of tissues appears to have been recognized 

 by a number of biologists including Wolff (1759), de Mirbel (1802). 

 Oken (1805), and Lamark (1809). From 1824 to 1830. works of Dutro- 

 chet, Turpin, and Meyers among others not only confirmed the univer- 

 sality of cellular structure but also hinted at the concept of cellular 

 autonomy in both the morphological and physiological sense. In 1831 

 Robert Brown described the nucleus; in 1832 Dumortier reported on 

 cell division in algae, and from 1835 to 1839, von Mohl sketched many 

 features of mitosis. These workers might be considered founders of the 

 specialized aspect of cytology sometimes known as karyology which was 

 to hold the center of the stage from the late 1800's to the late 1930"s. 

 This promising start, however, was slowed somewhat by the rather wide 

 acceptance of Schleiden's erroneous views on cell replication. Between 

 1840 and 1860 the work of von Mohl, Nageli, Remak, and Virchow 

 provided strong evidence for the idea that every cell is derived from a 

 pre-existing cell by some type of division. As this idea gradually became 

 established it led rather directly to the notion of cell lineage and the 

 tremendous work beginning in the late 1800's and continuing to this 

 day on the mechanics of cell and nuclear replication. In 1882 Flemming 

 described somatic division in considerable detail and applied the term 

 "mitosis" to the process. His description, based on his own work together 

 with that of many other observers including van Beneden and Stras- 

 burger, differs little from current views except for the erroneous notion 

 that, during interphase, chromosomes were hooked together in end to 

 end association as a continuous spireme. During the last two decades of 

 the 19th century, two other developments of major importance occurred. 

 Oscar Hertwig in a series of studies showed that fertilization involved 



THE CELL CONCEPT / 3 



