. Journal of morphology. Protopterus(Budgett 01; Kerr 09); and Lepidosiren (Kerr 00, 01 and 09).With respect to inequality in the cleavage, Lepidosiren in partic-ular closely approaches the condition in Cryptobranchus andNecturus. The cleavage of Polypterus (Kerr 07) bears a generalresemblance to that of Amblystoma and the frog. Stage 7: {figs. 103 to 105; 215 and 216). This stage is charac-terized by a doubling of the number of cells found in the precedingstage, and by a slight extension of the region occupied by themicromeres. The stage is reached about four hours later thanStage 6. Figures
. Journal of morphology. Protopterus(Budgett 01; Kerr 09); and Lepidosiren (Kerr 00, 01 and 09).With respect to inequality in the cleavage, Lepidosiren in partic-ular closely approaches the condition in Cryptobranchus andNecturus. The cleavage of Polypterus (Kerr 07) bears a generalresemblance to that of Amblystoma and the frog. Stage 7: {figs. 103 to 105; 215 and 216). This stage is charac-terized by a doubling of the number of cells found in the precedingstage, and by a slight extension of the region occupied by themicromeres. The stage is reached about four hours later thanStage 6. Figures 103 and 104 show a fairly representative egg in thisstage. The cells in the region of the animal pole are markedlylarger than the other micromeres. This condition may be dueto one or both of two factors: (a) the flattening of the cells com-posing the roof of the segmentation cavity; (b) a slower rate ofdivision in these cells, as noted in Stage 6. There is marked JOURNAL OF MORPHOLOGY, VOL. 23, NO. 3 478 BERTRAM G. SMITH.
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Keywords: ., bookcentury1900, bookdecade1, booksubjectphysiology, bookyear1912
