MUSEUM OF COMPARATIVE ZOOLOGY. 331 



I am strengthened in my belief that the phenomena described by 

 Brandt are only more extensive exhibitions of what Warneck has de- 

 picted, by the fact that Brandt has himself cited the observations of the 

 same author, and even called attention to Figs. 3' - 5' of the above-men- 

 tioned plate in confirmation of his theory. 



BiscHOFF (77), to whom Embryology owes so much, has recently con- 

 tributed to the discussion of the questions under consideration, without, 

 however, bringing new material to the elucidation of the subject. 



Two points of very general interest receive his attention : — (1.) The 

 unreliable methods of investigation, by means of hardening and stain- 

 ing reagents, etc., which have recently become so popular, are respon- 

 sible for misunderstandings and misconceptions which otherwise would 

 be avoidable. (2.) The greatest confusion as to the nature of the animal 

 cell has arisen through a confounding of its morphological with its physio- 

 logical nature. While all agree that the cell is physiologically an ele- 

 mentary organism^ things the most diverse, from a morphologico-histologic 

 standpoint, are indiscriminately called cells. The same confusion is 

 responsible for the idea that the e^g is a primary cell. " Meiner auf 

 Erfahrung, so weit sie reicht, gebauten Ansicht nach, ist nur das Keim- 

 blaschen eine wahre primare und die einzige Zelle, von der bei dem nicht 

 in der Entwicklung begriftenen Ei die Rede sein kann, und das Ei selbst 

 wird am passendsten ganz allgemein als eine Umhiillungs-Bildung einer 

 Zelle aufgefasst. Ich glaube ferner, dass jedes reife Ei an seiner primd- 

 ren Bildungsstdtte im Eierstocke nur, aber auch immer, aus Keimblaschen, 

 Dotter und Dotterhaut besteht." (p. 12.) 



As regards the fate of the nucleus during segmentation, although 

 granting that the question has not reached a final elucidation, Bischofl: 

 (p. 43) evidently inclines to the side of Auerbach and those who believe 

 in its dissolution at each act of division. Were Bischoff' to write in the 

 light of what has been described within the past two years, it may fairly 

 be doubted if he would persist in saying that new nuclei are formed quite 

 independently of the old nucleus ; * there is already too much evidence, 

 independent of the supposed deceptive appearances produced by reagents, 

 to make this position longer tenable. 



It seems incumbent on those who hold, with Bischoff, that the germi- 

 native vesicle is not a cell nucleus^ to explain why the vesicle undergoes 

 the same modifications previous to the formation of the polar globules 



* "Bei der Einleitnng zur ersten Theilimg das Keimblaschen und sein Kern 

 schwinden, nnd ein neuer Kern sich tmahhdngig von diesen bildet. Was das erstemal 

 geschieht, wird auch wolil das zweite- und drittemal gescheben." The original is not 

 Italicized. 



