SIZE VARIATION IN TRACHEARY CELLS. 151 



merely of readjustment consequent upon the first. It is probable 

 that the number of cells is approximately the same in both cases." 

 Similar phenomena are recorded by Winkler (lOKi) and Tupper and 

 Bartlett (lOlO & 19IS). The work of Gregory (1911) and Keeble 

 (1912), on the other hand, indicates that in giant forms of Primula 

 sinensis, which have larger cells than normal, there is an increase in 

 the size, but not in the numb(T of chromosomes. 



Morgan (1904) and Chambers (1908) find that the eggs laid by a 

 given individual may vary greatly in size, and the latter investigator, 

 who questions the doctrine of the fixity of cell size, considers that body 

 size and cell size are proportional to the size of the eggs from which the 

 animals are formed. Popoff (1908) also supposes that body size is 

 determined by the size of the reproductive cells, but Conklin (1912a), 

 as a result of his later investigations upon Crepidula, concludes (p. 

 186): "In the different species of this genus the size of the germ 

 cells does not determine the size of the adult (Popoff, Chambers). 

 Within the same species differences in body size are due in the main to 

 differences in cell number, the cell size being approximately constant." 



It is to be noted, in passing, that in many of these investigations 

 which tend to emphasize the constancy of cell size or cell number in 

 specific animals or plants, scant attention is given to the work of 

 botanists ^ and zoologists who concern themselves with the study of 

 variations due to environmental factors. Heumann (1850), Mor- 

 purgo (1888 and 1889), Frank (1895), Gauchery (1899), Lippold 

 (1904), Stoppenbrink (1905) and Morgulis (1911) describe a number 

 of dwarfs or depauperate plants or animals which are composed of 

 smaller tissue-cells than normal individuals or giants. However, it 

 is noted, particularly by Morpurgo, Gauchery and Morgulis that 

 different categories of tissues may behave very differently during 

 inanition. Kraus (1869-70) emphasizes the fact that the cells of the 

 long internodes of etiolated plants are longer than those of plants 

 grown under normal illumination, and MacCallum (1898) calls atten- 

 tion to the fact that the increase in the musculature of an adult and 

 muscular hypertrophy may be due to an increase, not in the number, 

 but the size of the muscle fibers. 



The investigations of Sanio (1872), Haberlandt (1882), lUing (1905), 



3 The works of Areschong, Brenner, Bonnier, Costantin, Derschau, Dassqn- 

 ville, Dufour, Eberdt, Eberhardt, Frank, Gcneau de Lamarliere, Grosglik, 

 Haberlandt, Hesselman, Johow, Kohl, Lesage, Mer, Nordhausen, Pick, 

 Sauvageau, Schuster, Stahl, Tschirch, Vesqiie, Volkens, Weiss, Zinger and 

 many others, who studied the effects of light, temperature, moisture, nutri- 

 tion, etc. upon the form and structure of plants, contain numerous incidental 

 references to variations in cell size, but unfortunately few exact measurements. 



