On the Murpholofjy and Physiolofjy of tlic Cell. 207 



arising by tlie process which I have termed interlaminar 

 gemmation ai)peared at first perfectly homogeneous, never 

 exhibiting a nucleus, even on treatment with reagents, while 

 the older and larger ones possessed a distinct nucleus and 

 nucleolus. Secondly, in the even more remarkable case of 

 endogenous cell formation presented by the brown corpuscles 

 of UcJmius * (fig. 1), no nucleus is distinguishable until the 

 adult corpuscle has reached its full development. Such 

 cases as these demand careful reinvestigation, before the 

 invariable origin of nuclei from pre-existing nuclei can be 

 safely maintained. 



5. Passing now from the morphological aspects of the 

 nucleus to the physiological, tlie older view — of the nucleus 

 as a mere inert dense lump — need not detain us. Not only 

 do the wide chemical differences between the nucleus and the 

 surrounding protoplasm oppose this view, while the pheno- 

 mena of all multiplication tend to show that it is, on the 

 contrary, the seat of the activities of the cell, but it is 

 sometimes possible even to observe its movements. The 

 nucleus of many ova is capable of amoeboid movement ; f 

 linger J has observed similar movements both in normal 

 and in inflamed tissues. Schleicher § describes an easy 

 method of watching the movements of the nucleus in the 

 living cartilage cells of the frog's omosternum, and 1 1| have 

 described a regular oscillation of the nucleus from side to 

 side within the body of an infusorian. 



6. Thanks to the investigations of Flemming, Strasburger, 

 Klein, and others, we now know that the so-called granules 

 of the protoplasm of cells belonging to all kinds of animal 

 tissues are really the optical expressions of the thickened 

 intersections of a delicate network of denser filaments — the 

 stromxt, between the meshes of which lies the more fluid 



* Sur le Fliiiile Perivisceral des Oursius. Areli. d. ZooL, Exj). VIII. 



t Balfour, "Comp. Embryology,"!., 1880. 



X Uel). amceboid. Kernbeweguiig, etc., Med. Jalirb. AVien, 1878, p. 393. 



§ Jourii. Roy. Micro. Sci., 1880, p. 407. 



II («) Observations on the Histol. and Physiol, of Convoluta (Proc. Roy. 

 Soc, Lond., 1879); {h) Sur luie nouvelle sous-elasse d'Infusoires (Comptes 

 Rendus, 19th Dec. 1881). 



