ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 447 



of granules or rods, and the precise form alters with the phase of func- 

 tional activity. 



The Granula Theory.* — Prof. Arnold thinks that the solution of 

 the " riddle of protoplasm " would be greatly assisted by a knowledge of 

 the origin and importance of the " granula." During experiments on 

 exogenous and endogenous siderosis, he came to the conclusion that the 

 iron is contained in the cells in the form of granules. According to 

 the current doctrine, such granules are taken up by the cells by a phago- 

 cytic process ; but various facts made him doubt this interpretation, and 

 he has made a series of further experiments by injection of soluble and 

 insoluble iron salts into the lymph-sacs of the frog. The result of these 

 and other observations is to lead him to the conclusion that the granules 

 of sideroferous leucocytes are not grains of iron which have been taken 

 up, nor precipitates which have originated within the cell, but are un- 

 altered cell-plasmosomes, which have taken up the iron, modified it, 

 and combined it with their own substance. Further, the arrangement 

 of the sideroferous granules in other cells (such as connective-tissue- 

 cells, epithelial cells, liver-cells), whether in the case of exogenous or 

 endogenous siderosis, is the same as in leucocytes, and the granulated 

 appearances obtained in such cells by means of methylen-blue and neutral 

 red, are similar to those obtained in sideroferous cells — two facts which 

 tend to confirm the view just expressed as to the origin of the " granula." 

 As yet it is not possible to decide whether or not the plasmosomes can 

 give up their iron without undergoing degeneration, but the research 

 shows clearly that they are cell-organs of functional importance. 



Cell Studies.! — S. Prowazek briefly summarises a series of observa- 

 tions which he has made on the eggs of Echinus microtaberculatus, and 

 other cells and simple organisms. Immature eggs of Echinus show dis- 

 tinct " spinning activities " after fertilisation. Spermatozoa penetrate 

 into non-nucleated fragments of immature eggs, and produce the ordinary 

 radiating figures, but these are not followed by segmentation phenomena. 

 In the case of non-nucleated fragments of mature eggs, segmentation 

 may follow normally ; it may become irregular at the two-cell stage ; or 

 the furrows may appear after some delay and then disappear again ; or 

 the male pronucleus may divide without the division being followed by 

 segmentation. Non-nucleated fragments are frequently penetrated by 

 many sperms which, within the egg, seem to be strongly attracted towards 

 one another. By shaking segmenting eggs, various different types of 

 segmentation, such as discoidul, superficial, unequal, can be produced. 

 The attraction of eggs on sperms appears to be due to a substance pro- 

 duced in living protoplasm ; for non-nucleated fragments and eggs from 

 which the reserve substance has been removed attract sperms like un- 

 injured eggs. The spermatozoa are to a certain extent acrotropic, but 

 Engelmann's bacteria method gave a negative result in the case of eggs. 

 The tails of spermatozoa when torn off are non-motile unless the middle 

 piece is present ; but if this be present, they will continue to move even 

 if the distal end is also injured. Cilia, flagella, and the ciliated plates of 

 Cydippe, on the other hand, continue to move only when the whole organ 

 is intact. 



* Anat. Anzeig., xvii. (1900) pp. 346-54. 



f Zool. Anzeig., xxiii. (1900) pp. 305-9 (3 figs.). 



2 H.2 



