188 THE CELL-THEORY 



Untersuchungen iibcr die Kiit-^'ickclnng tier WirbeltJiiere 

 (Berlin, 1850-55), proved that in the frog's egg at least 

 segmentation was a simple process of cell-division, initiated 

 always by division of the nucleus. 1 



One point Remak left undecided the fate of the 

 Keimblaschen or egg-nucleus. It was generally held, even 

 so late as the 'fifties, that the egg-nucleus disappeared just 

 before segmentation began Bischoff clung to this belief 

 even in iS//. 2 Though Barry had held in 1839 that the 

 egg-nucleus does not disappear in segmentation, J. Muller 

 seems to have been the first actually to prove that it 

 forms by division the nuclei of the first two segmentation 

 spheres. He furnished the demonstration in the egg of 

 finfoconc/Kr mirabilis? and his paper was known to Remak, 

 who could not, however, observe a similar division of the 

 egg-nucleus in the frog. Muller's discovery was confirmed 

 for Oceania annata by Gegenbaur, 4 and for Notommata 

 sicboldii by Ley dig. 5 



In 1854 Virchow, 6 previously a supporter of Schwann, 

 crystallised the new views in the famous phrase Oinnis ccllnla 

 e cellula and gave wide publicity to them in his classical 

 lectures on Cellular Pathology, delivered in i858. 7 The new 

 doctrine of cell-formation was also taught by Leydig 8 in his 

 text-book of histology, published in 1857. 



The Schleiden- Schwann theory of the origin of cells by 

 generation in a cytoblastem was now definitely overthrown. 



The importance of the protoplasmic content of the cell 

 was brought into prominence through the work of Dujardin, 9 



1 See particularly Plate IX., figs. 3-7. 



- Ilist.-krit. BancrkutigeH zu den ncitestcn Mitthcilun^en ii. d. erste 

 Entwickelung d. Sdugethiereier^ Mtinchen, 1877. 



:! Monatsber. Akad. Wiss. Berlin, 1851. 



1 Znr Lehrc von Gcnerationswcchsel u. d. Fortpflanxen d. Mcduscn u. 

 Polypen. 



' U. d. Ban 11. d. system. Stellit/n; d Rndcrtltierc, 1854. 



" Arch f. path. Anat. rhys., vii., ])p. 1-39, 1854. Also in his Keitnige 

 s. sp,-<\ f'tit/i. it. Tlicrapic. 



~ J)ic Cclliilarf>,ttlwloit\ I'.crlin, 1858. 



" 1.1-hrlnich dcr I listolo^ic, 1857. 



:i Ann. Sci. n<it. (2) iii., pp. 108-9 and pp. 312-4, 1835. Also iv, 



PP 343-77- 



