THE NUCLEUS 



51 



given tissue, though it may vary considerably with the physiological 

 activity (Maige, 1923). 



The ratio of the volume of the nucleus to that of the cytoplasm in a 

 ceU is called the " nucleoplasmic ratio," or " karyoplasmic ratio." Many 

 years ago it was held by Sachs and Strasburger that the size of a meri- 

 stematic plant cell maintains a very definite relation to the size of the 

 nucleus, owing to a supposed limitation of the sphere of influence of the 

 nucleus. This latter conception has been emphasized anew by Winkler, 

 and parallel views have been expressed by several zoologists.'^ In the 

 case of certain terminal meristems of plants such a rule may well hold 



r.i-y-- 





■*■■ I jftv '•*^^ ■■ 



Fig. 22. — Peculiar nuclei. A, portion of nucleus from spinning gland of Vanessa 

 urticw. {After Korschelt, 1896.) B, Spirostomum ambiguum, with moniliform nucleus. 

 {After Stein.) C, nucleus from salivary gland of Chironomus; the chromatic material 

 is in a convoluted thread which ends in two nucleoli. {After Balhiani, 1881. See also 

 van Herwerden, 1910, 1911; Aherdes, 1912; Faussek, 1913; Tamer, 1921.) D, Chwnia 

 teres, with chromatic granules scattered throughout the body. {After Gruber, 1885.) 

 E, lobed nucleus from yellowing lily leaf. {After Goldstein, 1928.) 



true within limits, but the condition reported by Bailey (1920) in the 

 lateral meristem (cambium) shows clearly that it cannot have universal 

 application. The cambial initials may vary enormously in size with no 

 corresponding variation in the size of their nuclei; two such initials, one 

 of them having many hundreds of times the volume of the other, may 

 possess nuclei of approximately equal size. Tischler (1924, 19256) 

 connects the ratio in pollen with the process of germination. The 

 nucleoplasmic ratio has figured prominently in discussions of the problem 

 of senescence and differentiation.^ 



In a given kind of cell there is a relation between the size of the nucleus 

 and the number of chromosomes. In 1895 Boveri showed that the size 



7 Sachs (1892, 1893, 1895), Strasburger (1893), and Winkler (1916) on plant cells; 

 DoUey (1913) on nerve cells; Hegner (1919) on Arcella; Hegner and Wu (1921) on 

 Opalina; Dolley (1925) on pancreatic cells. 



» R. Hertwig (1889, 1903, 1904, 1908), Minot (1891, 1908, 1913), Conklin (1912), 

 Child (1915), Popoff (1907), Marcus (1908), Howard (1910), Howard and Schultz 

 (1910). See Wilson (1925, p. 236); also Faure-Fremiet (1925). 



