424 F, R. ROWLEY ON SOME POINTS IN THE STRUCTURE 



seem to be from the middle of the cell towards the periphery, 

 and then back again towards the nucleus, though there is con- 

 siderable irregularity in the movements of individual granules. 

 Careful observations suggest that the cause of these movements 

 must be sought for in the granules themselves, and not, as might 

 be supposed, in streaming movements of the protoplasm. 



Lauterborn details at considerable length the behaviour of 

 Biitschli's spherules towards reagents. In a concluding recapitu- 

 lation he defines them as vesicles tilled with a tolerably strongly 

 refracting viscid substance, and mentions as marked charac- 

 teristics of the external envelope its capacity for actively taking 

 up methylene blue during the life of the cell, and the readiness 

 w'ith which it may be stained by Delafield's haematoxylin. 



The part played by these bodies in the economy of the cell is 

 left an open question, but a study of the changes w^hich they 

 undergo during nuclear and cell division suggests that they may 

 contribute in some way to the formation of protoplasm. 



As previously mentioned, the occurrence of such spherules is 

 not confined to the Diatomaceae, Biitschli has recorded his 

 " roten Kornchen " in Cyanophyceae, in the green and colourless 

 plasma of Flagellata, and in the Algae Stigeoclonium and Chan- 

 transia. Lauterborn also notes the occasional occurrence of 

 granules staining deeply with haematoxylin and methylene blue 

 in the Desmidiaceae {Closterium ? sp,), as well as in certain Rhizo- 

 pods (Amoeba villosa, Arcella vulgaris, and Groviia mutahilis). 



The space at my disposal will not permit me to attempt any- 

 thing like a complete abstract of Lauterborn's observations on 

 nuclear and cell division in the Diatomaceae. The whole subject 

 is elaborately treated, and the illustrations bear eloquent testi- 

 mony to the excellence of the lenses employed, and the patient 

 care with which the drawings were executed. As an example 

 of the results obtainable by careful and persistent observation, 

 I will conclude by describing the various stages of mitosis in 

 Surirella calcarata, w^hich aifords special facilities for tracing the 

 various phases of division in the living cell. Lauterborn states 

 that this species may stand as a model for other forms in the 

 matter of cell division, so that, by giving his observations in this 



