In a previous article, the increase in weight and length of embryos and larvae of Amblystoma punctatum [= Ambystoma maculatum] was studied from animals living under natural conditions (Dempster, '30). Weight changes from the segmenting eggs to the period of metamorphosis could be described by a single sigmoid growth curve. The curves representing changes in length were not as simple as those dealing with weight. During the free-living period, it is true, the changes in length followed the sigmoid curve to metamorphosis [this is evident both from the above study and from the curves (B & C, p. 9) of Harrison ('29) on laboratory animals ; the curve by Stone ( '30) will allow similar interpretation]. During the earlier embryonic period, the changes in length must be considered differently. Patch ( '27) has described two periods of sigmoid linear increment previous to metamorphosis, one in the embryonic and the other in the larval period. Two phases were likewise found in natural conditions (Dempster, '30). No explanation of the difference between the curves of the one-and of the threedimensional measurement s has been advanced, The primary object of the present communication is further investigation of growth during the period of early development, involving the study of a uniform stock of animals under constant environmental conditions. The data presented here, along with the data in the literature upon the older specimens will probably allow certain generalizations on the gross increment of the salamander during its whole aquatic period.
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