398 NATURAL SCIENCE. June, 



Professor Miall states that, " In the Amphibia which undergo 

 transformation, the stage added to the life-history of the more 

 primitive forms is not the tadpole, but the frog or toad." This, it 

 seems to us, depends upon what part of the animal's life is taken as 

 a point from which to view the preceding stages. We must 

 remember that the tadpole represents a highly-modified stage of 

 development, and that in this are concentrated many chapters of the 

 evolution of the ancestry of this type among the fishes and gill- 

 breathing batrachians. This abbreviation or concentration of adult 

 characters has been termed acceleration by Cope and one of the 

 authors of this paper, and has been made the subject of special 

 researches conducted among Vertebrata and Invertebrata. The 

 results have been formulated into a law lately designated, by one of 

 the authors of this paper, as the law of Tachygenesis. In following 

 out genetic series it has been ascertained that the successive species 

 or genera do not repeat the characters of their ancestors in detail, but 

 abbreviate or shorten them in accordance with definite laws of 

 procedure. The characters first acquired during adult stages of 

 ancestors are not inherited at the same age in descendants. The 

 supposed tendency to inherit at the same age in closely approximated 

 living descendants is misleading, because, when one examines series 

 in time, one finds that inheritance at the same age is only true of 

 nearly contemporaneous individuals, and not even generally true of 

 any large number of these. In other words, even in members of the 

 same species, if a series of these in time be followed, there is 

 constantly expressed a tendency to inherit characteristics earlier than 

 the age at which they first appeared in ancestors. The terminal or 

 highly specialised members of series have also been found to skip 

 ancestral stages altogether, and these cases are cited, often by high 

 authority, as unaccountable examples of abbreviations, or falsifica- 

 tions of the embryological records, and also under other imaginative, 

 subjective appellations, showing that these authors are using their 

 fancy to eke out their knowledge of the facts. The abbreviations are 

 really the direct inevitable result of the continued action of the law of 

 tachygenesis. 



One of the very best examples is the Salamandva atva of the Alps, 

 which brings forth living young. The embryo really passes through 

 its aquatic gill-bearing stage in the ovary, and may, as has been 



their former area, and, as a consequence, the cells of their tissues flatten out, 

 forming a pavement epithelium. The pupal wing, therefore, is derived directly 

 from the hypodermis of the larva. Some of the hypodermic cells become modified 

 in the pupa, and form the scales ; others become elongated and bind the upper and 

 lower layers of the bag-like wing together, so that when the insect emerges from the 

 chrysalis, and the blood pressure within the wings causes them to expand, they are 

 prevented from bulging out into balloon-shaped bags, and become the large, thin, 

 flat organs of locomotion with which we are familiar. The area of the wing ot the 

 mature insect is more than five hundred times greater than that of the larva. The 

 pigments of the scales are derived from the * blood ' or hsemolymph of the pupa. 

 " Alfred G. Mayer, Cambridge, Mass., February 26, 1896." 



