lo Feb. 1909.] Elements of Animal Physiology. 85 



SOME DEBATABLE POINTS IN HEREDITY. 



Maternal Impressions.— That the offspring whilst still in the uterus 

 can be influenced by faulty nutrition or disease of the mother is admitted 

 by all; that it can 'be influenced by things witnessed or cogitated by the 

 niother is an idea as old as Holy Writ. While firmly believed in by the 

 majoritv of breeders it is regarded as due to unscientific observation by most 

 if not all expert biologists. 



Telegony. — This word is used for "the supposed influence of a pre- 

 vious sire on offspring subsequently borne by the same female to a different 

 sire." This also is believed in by most breeders, but all experiments at 

 biological laboratories and farms have failed to give a single instance of it. 



Inheritance of Acquired Characters. — Acquired characters are those 

 which result from the action of external agencies upon the organism in 

 contrast to those that arise or reside in the sexual cells. Thus, in man, 

 change of residence to a hotter climate will darken the skin ; certain trades 

 will give distinguishing characters of hand, skin, limb, and muscle ; a 

 skilful movem.ent repeated many times will give facility in performing the 

 movement through changes in the nervous system and the limbs. The 

 question arises — can these be transmitted to the offspring? Some of the 

 earlier upholders of the evolutionary theory believed strongly that such 

 was the case. A giraffe, for instance, was supposed to have acquired a 

 long neck through the perpetual stretching of it for many generations in 

 order to reach the leaves of trees. Though the subject is still sub judice it 

 may be stated that by far the majority of biologists declare that such trans- 

 mission does not exist. There is not only evidence against this view such 

 as the non-transmissibility of mutilations, but further it may be definitely 

 stated that there is no instance so far of supposed transmission of acquired 

 characters which cannot adequately be explained by assuming that variations 

 took place in the reproductive cells and that natural selection was able to 

 insure permanence to those animals that possessed an advantageous varia- 

 tion, and was able to weed out those that did not possess it. The repro- 

 ductive cells, both of ovary and testis, are set apart in a very early stage 

 of embryonic life and it is difficult to see how they could be affected by 

 alterations in an animal's structure due to the animal's own activity or to 

 the action of an altered environment. Of course malnutrition or disease 

 may influence the sexual cells like any other cells of the bodv but this does 

 not affect the argument. 



Variation. — The Darwinian doctrine of evolution assumed that varia- 

 tions of almost imperceptible character were constantly occurring. If a 

 variation were of any advantage it persisted through natural selection and 

 so in course of time the variation became cumulative. There is however 

 some evidence for the viev/ that, at any rate in plants, variations may arise 

 of unexpected magnitude and further that such variations do not arise at 

 all times in the history of a species or race but are limited to restricted 

 epochs. Thus all the specimens throughout the world of chelidonium 

 laciniatiim, a celandine, are descended from an ancestor that appeared in 

 1590 in the garden of an apothecary in Heidelberg. In 1887 Professor De 

 Vries found two new specimens of evenmg primrose in a deserted potato 

 field near Amsterdam. These bred on the whole true to type, but showed 

 unmistakable evidence of a power to alter by leaps and bounds and not bv 

 the slow changes which Darwin considered the rule. To this form of 

 variation Professor De Vries gave the name mutation. So far instances 

 of mutation have not been clearly demonstrated in animals though " sports" 

 are known and, of course, reversions to ancestral types. 



