United States or Colombia ? Vote for the TOP Country of the Week !
With regard to her books, she believed they would be little read after her death. To a considerable extent her judgment has been verified. Her writings were a continual seed-sowing, which later workers fertilised, and brought to maturity. They were republished in eleven volumes in 1830.
On the other hand, examples of artificially induced development of eggs, not fertilised, are very few. The first known came accidentally to notice. Female silkworm moths reared in confinement sometimes lay eggs when kept apart from the male, and these have been found to hatch, and give rise to caterpillars, which were not reared to maturity.
I may add parenthetically that in most fish families the eggs are fertilised after they have been laid, instead of before, which no doubt accounts for the seeming anomaly. Still, good mothers too may be found among fish, though far from frequently. One of the Guiana catfishes, known as Aspredo, very much resembles her countrywoman the Surinam toad in her nursery arrangements.
What more appropriate parentage could be invented for the corn which springs from the ground that has been fertilised by the water of heaven? It is true that the land of Egypt owed its fertility directly to the Nile and not to showers; but the inhabitants must have known or guessed that the great river in its turn was fed by the rains which fell in the far interior.
In this case reduction of the chromosomes does not occur at all, the eggs develop with 2N chromosomes and all develop into females. Under unfavourable conditions reduction or meiosis occurs, and two kinds of eggs larger and smaller are formed, both with N chromosomes. The larger only develops when fertilised and give rise to females with 2N chromosomes.
And when she was left alone, when there was no one near to comfort or strengthen, a great silence fell upon her. For she indulged no stormy sorrow; her grief was a still rain that fertilised and made fragrant her higher self.
When the ovum or ova are not fertilised the development comes to an end after a certain time, differing in different species of Mammals, and the membrane sloughs, returns to its original, state, and then begins the same process of development again.
If we admire the several ingenious contrivances, by which the flowers of the orchis and of many other plants are fertilised through insect agency, can we consider as equally perfect the elaboration by our fir-trees of dense clouds of pollen, in order that a few granules may be wafted by a chance breeze on to the ovules?
When the bee, thus provided, flies to another flower, or to the same flower a second time, and is pushed by its comrades into the bucket and then crawls out by the passage, the pollen-mass necessarily comes first into contact with the viscid stigma, and adheres to it, and the flower is fertilised.
These results tend to show that factors are not indivisible units, and segregation is rather the difficulty of chromatin or germ plasm from different race uniting together. It must be remembered that the fertilised ovum which forms one individual gives rise also to dozens or hundreds or thousands or millions of gametes.
Word Of The Day