increasing concentration of the sea-water (leading to a diminishing ãwater-contentã of the egg) retards the rate of segmentation and at length renders segmentation impossible; though nuclear division, by the way, goes on for some time longer.
Among many other observations of the same kind, those of Bialaszewicz77, on the early growth of the frog, are notable. He shews that the growth of the embryo while still within the {126} vitelline membrane depends wholly on the absorption of water; that whether rate of growth be fast or slow (in accordance with temperature) the quantity of water absorbed is constant; and that successive changes of form correspond to definite quantities of water absorbed. The solid residue, as Davenport has also shewn, may actually and notably diminish, while the embryo organism is increasing rapidly in bulk and weight.
On the other hand, in later stages and especially in the higher animals, the percentage of water tends to diminish. This has been shewn by Davenport in the frog, by Potts in the chick, and particularly by Fehling in the case of man78. Fehlingãs results are epitomised as follows:
| Age in weeks | 6 | 17 | 22 | 24 | 26 | 30 | 35 | 39 |
|---|---|---|---|---|---|---|---|---|
| Percentage of water | 97ôñ5 | 91ôñ8 | 92ôñ0 | 89ôñ9 | 86ôñ4 | 83ôñ7 | 82ôñ9 | 74ôñ2 |
And the following illustrate Davenportãs results for the frog:
| Age in weeks | 1 | 2 | 5 | 7 | 9 | 14 | 41 | 84 |
|---|---|---|---|---|---|---|---|---|
| Percentage of water | 56ôñ3 | 58ôñ5 | 76ôñ7 | 89ôñ3 | 93ôñ1 | 95ôñ0 | 90ôñ2 | 87ôñ5 |
To such phenomena of osmotic balance as the above, or in other words to the dependence of growth on the uptake of water, HûÑber79 and also Loeb are inclined to refer the modifications of form which certain phyllopod crustacea undergo, when the highly saline waters which they inhabit are further concentrated, or are abnormally diluted. Their growth, according to Schmankewitsch, is retarded by increase of concentration, so that the individuals from the more saline waters appear stunted and dwarfish; and they become altered or transformed in other ways, which for the most part suggest ãdegeneration,ã or a failure to attain full and perfect development80. Important physiological changes also ensue. The rate of multiplication is increased, and parthenogenetic reproduction is encouraged. Male individuals become plentiful in the less saline waters, and here the females bring forth {127} their young alive; males disappear altogether in the