. Journal of morphology. the principal changes in the antero-dorsal region during thisstage. It will be seen that there is a progressive addition oftransverse grooves posterior to the three that first appeared. Infront of Groove I the cephalic plate is traversed primarily by sixgrooves; of these Groove 1, which was noted in the precedingstage, has a very transitory existence and in most cases is lostin Stage 14; likewise the median portion of Groove 2 has oftendisappeared. Moreover in this or the following stage Groove4 disappears, following a marked depression and perhaps sub-mergence of the
. Journal of morphology. the principal changes in the antero-dorsal region during thisstage. It will be seen that there is a progressive addition oftransverse grooves posterior to the three that first appeared. Infront of Groove I the cephalic plate is traversed primarily by sixgrooves; of these Groove 1, which was noted in the precedingstage, has a very transitory existence and in most cases is lostin Stage 14; likewise the median portion of Groove 2 has oftendisappeared. Moreover in this or the following stage Groove4 disappears, following a marked depression and perhaps sub-mergence of the segment between it and Groove 3. A significant relation exists between Grooves I, II, III, etc., andthe intersomitic grooves which now appear just outside the neuralfolds; by an inspection of figures 165 to 176 it will be seen thatin all cases these are in direct apposition. Since the mcsoblasticsomites are the most characteristically segmented structures ofthe vertebrate body, it follows that the true segmental units of. 165 166 167 168
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Keywords: ., bookcentury1900, bookdecade1, booksubjectphysiology, bookyear1912
