260 BULLETIN OF THE 



the surrounding cell protoplasm, are corroborated by the deportment of nuclei 

 which remain miracellular, the only modifications being such as are naturally 

 referable to the intervention of a protoplasmic layer surrounding the nucleus. 

 Inasmuch as this protoplasm appropriates to itself a definite portion of the 

 available substance of the solution, it is clear that it must exert a greater modi- 

 fying influence when the solution is highly attenuated, than when it is more 

 concentrated, — a conclusion which accords with the observed phenomena. 



Of more importance for us than the confirmatory evidence of these views de- 

 rived from the study of the nuclei of muscle; cells, red blood corpuscles, etc., are 

 conclusions reached in the second division , of Auerba^ch's paper concerning the 

 origin, increase, and vital properties of nucleoli. ..,wijs'^..,*^„, ,j!i^.. i,-^i4XJ/5<J ^ikmi 



Contrary to the opinion then commonly aiccepted, that the nucleus normally 

 contains one. or two, almost threi^ or four nucleoli, Auerbach insists. that th^ 

 presence of more than four nucleoli is very often a typical condition, and that 

 their number may amount to a hundred or more in extreme cases. This con- 

 dition is as a rule the result of successive self-divisions of previously existing 

 nucleoli, and the solitary nucleolus often has the same origin ; the latter, how- 

 ever, may have an independent origin (Neubildung). 



On the strength of his own observations in the case of frogs' eggs and the 

 blastoderm of Musca vomitoria, supported by evidence drawn from previous 

 observers, Auerbach concludes that in a certain first stage of embryonic develop- 

 ment in the eggs of vertebrates, articulates, and worm^., the nuclei of the young 

 cells are destitute of nucleoli. It may, moreover, be supposed, he says, that 

 this enucleolar condition is for animals a constant i^ement of a general law c^ 

 development (p. 89). ^> ,., ■ .^ ^^ 



In further elaboration of Reichert's law of successive differentiation th^ author 

 concludes that in the beginning of organic life there is present only protoplasm, 

 with or without yolk elements. In a second stage a differentiation of the pro- 

 toplasm results in the formation of a homogeneous nucleus in the centre. A 

 third stage is characterized by the appearance of a nucleolus in the centr^, and 

 a nuclear wall at the periphery of this nucleus. The last-nientioned structures 

 are believed to arise directly from the protoplasmic body, ©f the cell rather- thai} 

 from a differentiation of the nucleu^f-- thenuKileolus,.io amse by the detachment 

 of protoplasmic molecules from the protoplasm immediately surrounding the 

 nucleus, which then migrate toward the centre of the, soft nuclear mass (p. 84). 

 Finally, a fourth stage is characterized by the appearance of intermediary 

 spherules (Zwischenkiigelchen) between nucleolus and nuclear wall. In case 

 division ensues, the nuclear structures mentioned may be directly transmitted to 

 the daughter nuclei, or it may be that the daughter nuclei are at first destitute 

 of nucleoli, 



Auerbach brings to the discussion of the relation between uninucleolar and 

 multinucleolar nuclei an extensive series of observations upon various tissues 

 of vertebrates, from which he feels justified in maintaining the existence of a 

 parallelism between the Amniota and the Anamnia in so far as regards tl^ie 

 predominance of multinucleolar nuclei in the higher represeritatives,,of, each 



