Weismann sentence example
- The next step is illustrated by the female gonophores of Cladocoryne, where the radial and ring-canals F G H Modified from Weismann, Entstehung der Sexualzellen bei den Hydromedusen.
- Weismann has also ingeniously argued from the structure of the egg-cell and sperm-cell, and from the way in which, and the period at which, they are derived in the course of the growth of the embryo from the egg - from the fertilized egg-cell - that it is impossible (it would be better to say highly improbable) that an alteration in parental structure could produce any exactly representative change in the substance of the germ or sperm-cells.
- Thus the occurrence of blind animals in caves and in the deep sea was a fact which Darwin himself regarded as best explained by the atrophy of the organ of vision in successive generations through the absence of light and 1 Weismann, Vererbung, &c. (1886).
- Weismann, however, from theoretical considerations and from analysis of supposed cases has at the least thrown doubt on the transmission of acquired characters.
- The conceptions of Weismann afford no ground for rejecting fluctuating variations from the materials for the production of species.Advertisement
- The evidence that the correlation between sexually produced brethren is the same as that existing between the asexually repeated organs on an individual body renders it impossible to accept Weismann's view that one of the results produced by the differentiation of animals and plants into two sexes is an increase in the variability of their offspring.
- Weismann, however, doubts these conclusions, and having found a spermaster in every one of the eggs that he examined from workercells, and in only one out of 272 eggs taken from drone-cells, he supports Dzierzon's view, explaining the single exception mentioned above as a mistake of the queen, she having laid inadvertently this single fertilized egg in a drone instead of in a worker cell.
- Darwin died some years before the controversy upon the possibility of the hereditary transmission of acquired characters arose over the writings of Weismann, but Wallace has freely accepted the general results of the German zoologist's teaching, and in Darwinism has presented a complete theory of the causes of evolution unmixed with any trace of Lamarck's use or disuse of inheritance, or Buffon's hereditary effect of the direct influence of surroundings.
- Weismann, all the leading biologists had either subscribed to the telegony doctrine or admitted that "infection of the germ" was well within the bounds of possibilities.
- Even Professor Weismann did not deny the possibility of the offspring throwing back to a previous mate.Advertisement
- In assuming this attitude Professor Weismann decidedly differed from Herbert Spencer, who some years ago mentioned that he had evidence "enough to prove the fact of a previous sire asserting his influence on a subsequent progeny."
- This inference has involved him in much controversy with the ultra-Darwinians of Weismann's school, who deny the possibility of the inheritance of acquired characteristics altogether.
- This the present writer is inclined to doubt, considering that he has received examples of the normal Amblystoma tigrinum from various parts of Mexico, and that Alfred Duges has described an Amblystoma from mountains near Mexico City; at the same time he feels very suspicious of the various statements to that effect which have appeared in so many works, and rather disposed to make light of the ingenious theories launched by biological speculators who have never set foot in Mexico, especially Weismann's picture of the dismal condition of the salt-incrusted surroundings which were supposed to have hemmed in the axolotl - the brackish Lago de Texcoco, the largest of the lakes near Mexico, being evidently in the philosopher's mind.
- Similar results having been obtained with horses and asses, there is no escape from the conclusion that the telegony tradition is not confirmed by such methodical investigations as were suggested some years ago by Professor Weismann (see Cossar Ewart, The Penycuik Experiments, 1899) Telegony in Dogs.