These gentes were usually such as had been formed by the segmentation of an original gens.
The segmentation of the nucleus precedes and then continues with the segmentation of the yolk.
After segmentation the blastoderm becomes divided, as in Elasmobranchii, into two layers.
It lies ventral to the nerve cord, and shows no trace of segmentation.
Impregnation is external and the segmentation is nearly regular (fig. 1).
They also show what might be considered as faint traces of segmentation.
The lower pole of the ovum is then formed of a mass in which no traces of segments or segmentation furrows can be detected.
The segmentation has already been fully described, pp. 118 and 119.
Rohon entitles his discovery 'the segmentation of the primordial cranium.'
The segmentation is centrolecithal and regular (fig. 237 A).
segmentation seg·men·ta·tion (sěg'mən-tā'shən, -měn-)