3J6 DR. E. KLEIN. 



Fronimann^ describes, in accordance -with Heitzmann, a 

 minute network of fibrils in the nuclei of blood-corpuscles of 

 Astacus Jluviafilis ; this network passes through the nuclear 

 membrane into a similar network of the substance of the 

 blood-corpuscles. From a reference quoted in a note (" Zur 

 Kenntniss des Zellkerns"), by Professor W. Flemming, in 

 ' Centralblatt f. med. Wissen./ 18TT, No. 20, I learn that 

 C. Frommann had observed and described already in 1867, 

 i.e. before Heitzmann, a network of fibrils in the nuclei of 

 many kinds of cells. 



Biitschli- observed in the neuclei of coloured blood corpus- 

 cles of frog and newt minute fibrils with granular thicken- 

 ings, but no nucleolus, as asserted by Ranvier. 



Schwalbe* made extensive studies on the nuclei of gan- 

 glion-cells of the retina and found their nucleoli often pos- 

 sessed of minute filamentous prolongations ; the nuclear 

 membrane shows prominences on its inner surface. Nucleolus 

 and filaments, nuclear membrane and its prominences repre- 

 sent what Schwalbe designates as ' Nucleolarsubstanz,' and 

 he distinguishes it from the rest of the nuclear matter, 

 which he calls ' Kernsaft' (nuclear juice). Schwalbe thinks 

 that this arrangement of the ' Nucleolarsubstanz' is brought 

 about by a process of vacuolation, which in young indivi- 

 duals is of much greater extent than in older ones. Accord- 

 ing to Schwalbe between the bulky mass of the nucleoJar 

 substance in small young nuclei and the small rudiments 

 of this same substance — limited entirely to the membrane of 

 the adult nuclei, in which the nucleolus is not present 

 any more, there are intermediate stages brought about by 

 vacuolation, one of which is the above-mentioned condition, 

 viz. nucleolus with processes, smaller or larger prominences 

 on the inner surface of the nuclear membrane. 



Kupffer^ maintains of the liver cells of frog, of the odon- 

 toblasts, of the epithelial cells of the urinary tubules, and of 

 the cells of salivary gland of Pcr'q^laneta oricntalis, that 

 their substance is composed of a hyaline (non-fluid) ground 

 substance, 'Paraplasma,' and of a granular-fibrillar contrac- 

 tile * Protoplasma' embedded in the former. The relation 



' "Zur Lehre von der Structur der Zelleii," 'Jenaische Zcitsclirift f. 

 Naturw.,' Bd. ix, p. 2S0. 



- "Studien uber die ersteu Eiitw," &c., * Abhaudl. d. Senkenbergisclien 

 Naturf. Gesellscli.,' Bd. x. 



3 "Bern, iiber d. Kerne d. Ganglienzellen," 'Jenaische Zeitschrift f. 

 Naturw.,' Bd. \, p. 25. 



•• " iJbcr Diffrreiizirunp d. Protoplasma an den Zcllcn thicrisclicr Gcw.," 

 ' Schriftcn dcs Naturw. Vercins f. JScliloswig-Uolslcin.,' llcft iii, und 

 'Bcitr. 7.. Anal. 11. Physiol. Fesblir. f. Carl Ludwig,' 1S75. 



