ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 821 



up in lycopodium-powder, either side by side or one over another, and 

 then subjected to pressure in various directions. The forms resulting 

 are described from a mathematical point of view in regard both to 

 their surfaces and to their contents, and the laws thus obtained are 

 then applied to account for the various forms of cells found in the 

 animal and vegetable kingdoms. 



Structure of the Nucleolus.* — Dr. E. Zacharias has carefully 

 examined the structure, properties, and functions of the nucleolus, 

 taking as his chief illustration, on account of their size, the nucleoli 

 from the inner layers of the wall of the ovary of the snowdrop. In 

 uninjured cells in which the currents of protoplasm are still kept up, 

 the nucleolus appears under water perfectly homogeneous, in contrast 

 to the fine granulation of the rest of the nucleus. When, on the 

 contrary, the cells have been ruptured, the entire mass of the nucleus 

 except the nucleolus swells up, the latter forming a shining sharply 

 defined body, which is usually soon expelled from the ruptured 

 nucleus. In the nucleolus itself may be detected two substances of 

 different appearance, a central mass of stronger refringency and 

 vesicular character, surrounded by a homogeneous ground-substance. 

 The same differentiation is produced by absolute alcohol. Carmine 

 stains chiefly the central mass. Treated with ferrocyanide of potas- 

 sium and chloride of ii'on, the nucleolus is coloured blue, and contracts, 

 leaving a space between it and the ground-substance of the nucleus ; 

 the diameters of nucleolus, cavity, and nucleus, are about in the 

 proportion of 3, 4, and 10. The nucleolus has the appearance under 

 these circumstances of a fine-meshed framework with coloured strands. 

 In artificially prepared gastric juice, the nucleolus becomes pale and 

 swells up, while brightly shining granules of nuclein appear in the 

 rest of the nucleus. Longer immersion causes the nucleus apparently 

 to disappear, but it is again coloured blue by ferrocyanide of potassium 

 and chloride of iron, though reduced to about one-third of its original 

 size. Carmine does not stain it in this condition, and even a 10 per 

 cent, solution of chloride of sodium causes no change. 



Pieces of tissue heated for some days with 10 per cent, solution of 

 chloride of sodium and then examined in alcohol, rendered the 

 nuclei very pale, and showed that a large portion of their substance 

 was removed. A solution of carmine in very dilute ammonia stains 

 the nucleoli very rapidly and strongly ; while in a strongly acid 

 solution of carmine in acetic acid tlio nuclein body is very strongly 

 stained, tlie nucleolus remaining quite uncoloured, pale, and swollen ; 

 after a time it takes some colour, but remains lighter than the rest of 

 the nucleus. All these reactions show that the nucleolus consists 

 mainly of ulbuminoids in addition to plastiu, but that it contains no 

 nuclein. The same properties were found in tlio nucleoli of many 

 other plants, such as those of the bast-cells of Cucurbita Pepo, of the 

 filaments of Sidrogjjra, and of the nuclei in the asci of Peziza cinerea 

 and vegiculosa. 



The nucleoli resemble tho pyrenoids in consisting of albuminoids 



• Bot. Zt-., xliii. (l«8.'j) pj). 257-Gr), 27:{-8:i, 289-'JG. 

 Ser. 2.— Vol-. V. 3 11 



