8 THE GENERAL CHARACTERS OF CELLS, BY S. STRICKER. 



its occurrence appears to be subject to certain limitations, 

 especially if we consider the cells of cryptogams, and do not 

 start with the presupposition that, even in those cases where 

 no nucleus is visible, it must nevertheless be present." The 

 opinion of Briicke undoubtedly gains in weight, the more care- 

 fully the subject is considered. 



Max Schultze* has discovered a non-nucleated Amoeba 

 (Amoeba porrecta) in the Adriatic ; E. Hackelf a larger non- 

 nucleated Protista (Protogenes primordialis) in the Mediterra- 

 nean ; and lastly, CienkowskiJ has described two non-nucleated 

 monads, namely, Monas amyli and Protomonas amyli. Hackel 

 states, in reference to his protista, that it propagates by division. 



It is, moreover, a fact, first made known by Y. Baer, that the 

 germinal vesicle of the impregnated egg that is, the nucleus of 

 the ovum vanishes, and that the further process of develop- 

 ment commences with a new generation of nuclei. I must 

 express, in regard to the egg of the frog, my entire concurrence 

 with V. Baer in regard to the question at issue. I have under- 

 taken a great number of comparative investigations between 

 fertilised and unfertilised ova in the same mode as that em- 

 ployed by him, and have found a germinal vesicle in the latter 

 as a rule, whilst in the former there is only a cavity left, or even 

 a total absence of any trace of its existence. But the ova of the 

 more highly organised animals pass, as is well known, through 

 various stages or grades of development till they reach a state 

 in which their life terminates, and these ascending stages of deve- 

 lopment may, without straining the point, be generally compared 

 with the ascending grades of organisation which characterise 

 the existing world. It is therefore but a step to admit that the 

 commencing stages of the process of development correspond 

 to the lowest forms of animal life. The existence of the non- 

 nucleated cryptogams and of the non-nucleated protista which 

 are now known, speak strongly in favour of such an analogy. 



But if we desire to be logical, if we do not desire to advance 

 the statement that the non-nucleated bodies of the lower plants 



Organism der Polythalamien, 1854. 

 Zeitschrift fur wiss. ZooL, 1865, Band xv. 

 Max Schultze's Archiv, 1865. 



