THE CELL DOCTRINE. 129 



remainder of the cell, which are called nuclei. These 

 nuclei, although strikingly constant, are not invari- 

 ably present, as pointed out by Briicke,* in 1861, in 

 the cells of cryptogams, and confirmed by the earlier 

 discovery in 1854, of a non-nucleated amoeba (Amoeba 

 porrecta) by Max Schultze,t in the Adriatic Sea ; 

 also later by Hffickel;]^ and Cienkowski§ in their dis- 

 coveries in 1865, by the former of a non-nucleated 

 protozoon (Protogenes priraordialis) in the Mediterra- 

 nean, and by the latter of two non-nucleated monads 

 (Monas amyli and Protomonas amyli). Stricker's| 

 observations on the fecundated egg of the frog in- 

 cline him to adopt the view of Briicke, and omit 

 the nucleus in a theory of elementary organiza- 

 tion. Such facts as these prove erroneous the defini- 

 tion of a cell proposed by Leydig and Max Schultze, 

 " protoplasm surrounding a nucleus," and the defini- 

 tion more recently accepted by Virchow,T that a cell 

 is " a nucleus surrounded by a molecular blastema;" 

 though if we restrict ourselves to the cells concerned 

 in the organization of the higher animals, the latter 

 may be anatomically correct, but the former involves 

 the confusion already referi'ed to in the use of the 

 word " protoplasm," which is here applied to some- 



* Briicke, B.,Die Elementar-organisraen, p. 18-22, 1861. 



t Schultze Max, Organis. d. Polythalam. , 1854. 



X Hseckel, Zeitschr. f. w. Zoolog., 1865, Bd. xv. 



I Cienkowsky, Max Schultze's Archiv, 1865. 



y Strieker, S., in vol, i, p. 8, Strieker's Histology, New Syden- 

 ham Society's Translation, London, 1870; also p. 504, vol. iii, 

 London, 1873. 



\ Letter from Berlin, in Edinburgh Medical Journal, Febru- 

 ary, 1865. 



