ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 47 



Physicists have shown that a film of liquid, homogeneous and without 

 weight, can persist only if it forms a surface with a constant mean curya- 

 ture. Cell-membranes at the time of their formation fulfil this condition. 

 Many of the lower plants (e. g. Conjugatse) form figures of revolution, 

 either spheres or cylinders, &c. 



When a cell divides simultaneously into several others, the collection 

 of partitions forms a " system of laminae " ; and the division of cells in 

 endosperms and sporangia of plants fulfils, very approximately, the condi- 

 tion found in such systems, as to the angles at the junction of the partitions 

 and so on. In the most usual cases of binary division the new partition is 

 nearly at right angles to the old membranes, as Sachs has shown. 



In membranes which are not homogeneous the mean curvature, instead 

 of being constant, is at each point in inverse ratio to the tension. 



Structure of Glandular Cells.* — Dr. J. H. List sums up his results 

 as to the histology of mucous cells. He notes the distinction between the 

 threadwork and the interfilar substance, the varied arrangement of the 

 former, and the unequal staining of the latter, the independence of the 

 nucleus and its frequently flattened form, &c. As the goblet-cell approaches 

 the surface, and becomes more mature, the threadwork becomes better 

 developed. 



In the living cell subtle movement of the threadwork may be detected. 

 The nodes seem slowly to approach one another, and then retreat. List 

 regards as probable the suggestion of Eindfleisch, that the movement was 

 referable to altering adhesion between the two chemically different sub- 

 stances. 



During secretion the strands of the threadwork converge towards the 

 mouth, while the transverse connections are for the most part broken. In 

 the plug, expelled and disrupted meshes may be recognized, but the 

 interfilar mass is present in much greater proportion than in the theca. 

 Dr. List therefore suggests that an increase of volume in the interfilar 

 mass may be the main factor in the secretion, while the threadwork remains 

 more passive. In regard to the proportion between cell protoplasm and 

 secreted substance, the author found that the former was completely modified 

 at an early stage. 



Goblet-cells.t — Dr. J. H. List gives a detailed account of his researches 

 on goblet-cells. The memoir is introduced by a full historical critique of 

 relative observation. 



In describing the form of goblet-cells, Dr. List distinguishes those 

 without a basal process or foot containing the nucleus, and those with such 

 an appendage to the " theca " or body of the cell. The former are again 

 distinguished into stalked and unstalked forms. The various sizes in 

 different regions and organisms are tabulated. 



The content of the theca consists of a framework, with polygonal or 

 round meshes, and a homogeneous substance, less readily stainable, 

 occupying the meshes. The former is distinguished as the threadwork 

 (" Filarmasse ") and the other as the " interfilary " substance. Both are 

 described in detail. The contents of the foot are similar. The stalk 

 appears homogeneous and sometimes granular. The author was unable to 

 see any connection between the network of the cell and the intranuclear 

 network. The characters of the nuclei in the different forms are described, 

 karyokinetic figures were never observed, but multinuclear cells occurred. 



* Biol. Ceatialbl., vi. (1886) pp. 592-6 (Ber. 59 Versamml. Deutsch. Naturf., Beiliu, 

 1886). 



t Arch. f. Mikr. Anat., xxvii. (1886) pp. 481-588 (6 pis.). 



