120 NATURAL SCIENCE [August 1898 



they are strung. An explanation far removed from current theories 

 has forced itself on me — perhaps after all it is the achromatic 

 plasma (' linin ') of the nucleus whose fair and equal division is the 

 important matter, the final cause of karyokinesis. But the splitting 

 of a viscid thread is one of the most difficult mechanical feats to 

 accomplish. Suppose, then, that there is a certain polarity about 

 the granules of chromatin, through which, after their division, they 

 tend to recede from their fellows as far as possible ; through this 

 they will determine a splitting of the filament on which they are 

 strung. The close of nuclear division sees their task accomplished ; 

 and, as we should expect, the chromatic granules having fulfilled 

 this appointed task, now atrophy, and remain in this state till the 

 approach of a new cell-division determines a fresh growth of their 

 substance. According to this view the linin is the transmitter of 

 inherited properties, and the chromatin has a purely mechanical 

 function in karyokinesis. I may venture to predict that this 

 hypothesis will be shortly incorporated into the newest edition 

 of the germ-plasm theories ; for it avoids the many difficulties 

 due to the ascription of hereditary constancy to a substance so 

 subject to periodic atrophy and growth as the chromatin of the 

 nucleus. Marcus Hartog. 



Queen's College, Cokk. 



literature referred to. 



Hartog, Marcus, '91. — "Some Problems of Reproduction : a Comparative Study of 



Gametogeny, and Protoplasmic Senescence and Rejuvenescence." Quart. 



Joum. Micr. Sci., n.s., vol. xxxiii., pp. 1-79. (Dec.) 



— '97. — "The Fundamental Principles of Heredity." Nat. Sci., vol. 



xi., pp. 233-239 and 305-316. (Oct. and Nov.) 

 Hertwig, Oscar, '90.— " Vergleich der Ei- und Samenbildung bei Nematoden. Eine 



Grand lage fur cellulrire Streitfragen." Arch. Mikr. Anat., vol. xxxvi., pp. 



1-138, pts.i.-iv. 

 Strasburger, E , '94a.—" The Periodic Reduction of the number of the Chromosomes in 



the Life-history of many Organisms " [translation of a paper read at the Oxford 



Meeting of the British Association]. Ann. Botany, vol. viii., pp. 281-316. 



(Sept.) | 



— '94b.— Ueber periodische Reduction der Chromosomenzahl im Entwick- 



lungsgang der Organismen [the original paper from which the former was 



translated, but revised and extended after the discussion thereon in Section D. 



at Oxford]. Biol. Oentralbl., vol. xiv. pp. 817-838 and 849-866. 



