ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 341 



ance in the cavity of the nucleus, though the granular condition may 

 commence earlier. 



The nucleoles do not exhibit any structure, and differ altogether 

 from those of Spirogyra, the only feature which they possess in common 

 with these being their occurrence within nuclei. Went's statement 

 that they take part in the formation of the nuclear threads is incorrect. 

 When the wall of the nucleus becomes absorbed, the nucleoles disappear. 

 In Fritillaria this occurs at a very early period ; in Leucojum it takes 

 place more gradually. They are again formed in the daughter-nuclei. 



An incomplete karyokinesis sometimes takes place. 



Peculiar Kinds of Nucleus.* — Prof. H. Molisch finds three peculiar 

 kinds of nucleus, not hitherto described, all occurring in the latex or 

 mucilage of plants. 



(1) Bladder-nuclei ; furnished with a comparatively large sap- 

 bladder, resembling nothing else known either in the animal or vege- 

 table kingdom. These were found in the latex of several species of 

 Musa, of Aroideae, and of the hop, and apparently multiply by direct 

 division. The nuclei have the appearance of lying in large sap-vacuoles, 

 and are accompanied by peculiar crystals of an organic probably pro- 

 teinaceous substance, also imbedded in vacuoles. 



(2) Thread-nuclei : drawn out into enormously long threads or 

 knots of threads: — in the mucilage of the leaves of Lycoris and other 

 Amaryllideae. They are usually unbranched, and vary in length from 

 13 to the enormous magnitude of 1510 /a. Their breadth is in inverse 

 proportion to their length, varying between 16 and - l //.. 



(3) Giant-nuclei of species of Aloe. These are the largest yet ob- 

 served in the vegetable kingdom, measuring from 50-82 //. in length, 

 and from 20-46 fx. in breadth. 



Amitosis.f— Herr W. Pfeffer gives an account of Nathansohn's ob- 

 servations on direct nuclear division in Spirogyra (#. orbicularis) by the 

 action of ether. The nucleus divides gradually into two halves, which 

 separate from one another and occupy central positions in the daughter- 

 cells. Cell-division takes place in the same way as in mitosis, the 

 formation of the septum commencing at the periphery and proceeding 

 centripetally. Wheu again placed in normal conditions, karyokinetic 

 lakes the place of direct division. It is clear that, at least in Spirogyra, 

 mitotic and amitotic divisions may replace one another, and are so far 

 equivalent to one another that the product possesses in both cases the 

 same properties. Every cell preserves its full embryonal quality, i.e. 

 its capacity to regenerate the entire organism. It is probable that 

 ■Spirogyra possesses the property of propagating itself to an unlimited 

 •extent exclusively by amitotic division of the nucleus. 



Chromatolysis of the Nucleus. + — Sig. B. Longo describes a patho- 

 logical condition of the nucleus in cells of the bracts of Cynomorium 

 ■coccineum, corresponding to that known to zoologists as " pyenosis." The 

 chromatolytic condition begins with a contraction of the chromatin 



* Bot. Ztg., lvii. (1899) 1" Abth., pp. 177-91 (1 pi). 

 t Ber. Verhandl. k. saebs. Gesell. Wiss. Leipzig, li. (1899) pp. 4-12. 

 I Ann. r. 1st. Bot. Koma, ix. (1899) p. 7 (1 pi.). See Bot. Centralbl., lxxxi. 

 {1900) p. 400. 



