ZOOLOGY AND BOTANY, MICK08C0PY, ETC. 555 



and ZacBarias are stated and criticized. Naturally much space is 

 devoted to a discussion of tlie much disputed question of the behaviour 

 of the pronuclei. 



Cellular Statics.* — Prof. L. Errera has investigated the statics of 

 cell-form, comparing them with soap-bubbles. It is interesting to notice 

 that in the same year (1887), Leblanc, Fuchs, Errera, and Berthold 

 were independently at work on the same problem. 



At the moment of appearance the cell-membrane is extremely thin, 

 delicate, plastic, and changeable in its particles. Like similar fluid 

 lamellae, it tends to assume that form which would be taken by a 

 weightless fluid lamella under the same conditions, and to exhibit a 

 minimal surface and constant curvature. Apart from the mere shape of 

 the cell, questions of division, wall-formation, and the like are discussed 

 in a suggestive way. Even the thirteen conclusions, however, involve 

 technicalities which hardly admit of compression. 



Fusion of Lymphatic Cells into Plasmodia-! — M. A. Michel does 

 not accept the explanation of Mr. Geddes, by which the fusion of lymph- 

 cells of Lumbricus is compared to that seen in Myxomycetes. The 

 lymph when first collected contains a large number of flattened branched 

 cells ; after a few minutes' exposure to the air these become spherical in 

 form, with pointed projections ; some elongate and ramify into proto- 

 plasmic prolongations, which constantly change their form, especially if 

 placed in a warm chamber at 30°. In about half an hour these cells 

 form a plexus ; there is a gradual concentration. At the end of two or 

 three hours there are only rounded masses with peripheral prolongations. 

 The free cells give out a transparent protoplasmic layer which is often 

 much vacuolated and of such delicacy that its boundaries can only be 

 made out with difficulty ; some of the cells meet and form a continuous 

 layer with spaced granular centres, each with a nucleus, or they form 

 fine complicated or amoeboid plexuses. Finally, the masses die at the 

 end of some hours, and break up into rounded elements, each of which 

 has its nucleus. 



The author points out that, even in the warm chamber, the living 

 masses have no general movements ; the only changes which occur are 

 due to the general contraction and rupture of very extended filaments. 

 If isolated moving cells are carefully followed it will be seen that, 

 among the massed cells, some will separate from and leave the fused 

 mass. These masses, when observed with a high magnifying power, do 

 not present the homogeneity which would be exhibited if the fusion 

 were real. The circular striae which may be noticed suggest that there 

 has been a tangential displacement of imprisoned cells. The best 

 results are obtained with the vapour of osmic acid, and staining with 

 picro-carminate of ammonia ; chromo-nitric liquid (Perenyi's fluid) shows 

 the distinct cells with their nuclei. 



In addition to the objections raised by these considerations, the author 

 points out that death occurs successively at different points, and that 

 each element may be made to swell by water into an agglomeration of 

 vesicles pressed one against another, and he concludes that the fusion of 

 the cells is only pseudo-plasmodic. 



» Biol. Centralbl., vii, (1888) pp. 728-31 (60 Versamml. Deutsch. Naturf. 

 Wiesbaden, 1887). 



t Comptes Eendus, cvi. (1888) pp. 1555-8. 



