American journal of physiology . Figures. — A series of rapid successive changes in an unfertilized Chictopterus 4 minutes the eggs appeared in the 2-cell, 3-cell, 2-cell, 1-ceIl, 2-cell, and 1-cellstage again. The plane of cleavage was different in each case. an altogether different position of the cleavage plane (, ).In a few seconds the two spheres fused into one cell, and a number ofsmall droplets appeared below (). Of course it is impossible totell whether or not these single spheres or droplets contained phenomena are of importance for the mecha
American journal of physiology . Figures. — A series of rapid successive changes in an unfertilized Chictopterus 4 minutes the eggs appeared in the 2-cell, 3-cell, 2-cell, 1-ceIl, 2-cell, and 1-cellstage again. The plane of cleavage was different in each case. an altogether different position of the cleavage plane (, ).In a few seconds the two spheres fused into one cell, and a number ofsmall droplets appeared below (). Of course it is impossible totell whether or not these single spheres or droplets contained phenomena are of importance for the mechanics of develop-ment, inasmuch as they show that the bulk of the ^^^ is liquid, andthat in the case of Chaetopterus its viscosity is very small and lessthan in the case of the sea-urchins egg. It is hard to understandwhat kind of structure could be preformed in a liquid mass of suchlow degree of viscosity beyond the differentiation into nuclear andprotoplasmic material and possibly Artificial Parthenogenesis. 445 The appearance of the trochophores originating from unfertihzedeggs is exactly hke that of those arising from fertilized eggs, if onecompares equal stages of development. Fig. 2 gives no good ideaof the trochophore, inasmuch as the latter is at first spherical. Fig. 4shows two parthenogenetic trochophores, drawn by the camera withthe exception of the cilia, which are more or less diagrammatic. Theeggs from which these trochophores originated had been treated withKCl. It is hardly necessary to mention that the appearance of thetrochophores developing from parthenogenetic eggs depends greatlyupon the treatment the ^^2, had received. I mentioned this point inconnection with the artificial parthenogenesis of ^ A point which must be discussed is theduration of life of the parthenogenetictrochophores. All the Chaetopterus larvae,those that developed from fertilized eggs aswell as those that developed from unferti-lized eggs, died after two days.
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Keywords: ., bookautho, bookcentury1800, bookdecade1890, booksubjectphysiology
