“Maintenance of Normal Structure in Heteroploid Salamander Larvae, through Compensation of Changes in Cell Size by Adjustment of Cell Number and Cell Shape”, 1945-12 (; backlinks):
Young triploid and pentaploid larvae of Triturus viridescens and other species of salamanders are of normal dimensions because the size of the nuclei and cells, which increases in proportion to the chromosome number, is neutralized by a corresponding decrease in the number of cells. In haploid larvae, an increase in cell number brings about at least a partial compensation of the smaller cell size
In organs with single cell layers normal dimensions and structure are maintained in heteroploid larvae by changes in cell number combined with changes in the shape of the individual cells which show a progressive flattening with increase in chromosome number. The diameter of the wall of the pronephric tubules and pronephric ducts, and the thickness of the epithelium of the lens of the eye thus remain about the same from the haploid to the pentaploid levels.
In the retina of young pentaploid larvae the number of rows of cells in the ganglionic and inner nuclear layers is reduced to about 1⁄2 of that in the diploid so that the total diameter of the retina is actually smaller in the pentaploid. In the single layer of visual cells, on the other hand, the nuclei are wider in the pentaploid, but of about the same height as in the diploid so that the diameter of this nuclear layer remains about the same.
These observations show that in the amphibian embryo both cell number and cell shape may be modified to allow the formation of organs of normal size and structure. This indicates that both are subject to some control by the developing organism.
…From these observations one may conclude that both cell number and cell shape are subject to some controlling mechanism that operates during development and tends to produce a normal end result, even to the very details of organization, in spite of the apparently irreversible changes in cell size.