JULT 17, 1914] 



SCIENCE 



83 



SoUas estimates the total thickness at ahout 

 80 kilometers and the average rate of 

 deposition of the layers at 30 cm. per 

 century. From these numbers we may find 

 an age of 26 millions of years for the 

 collective deposition of all the geological 

 layers. Calcareous rocks have been built 

 by organisms and mainly by corals and 

 molluscs. These have made use of the lime 

 added to the sea by the rivers. Dubois 

 has calculated on the one hand the vfhole 

 thickness of these rocks and on the other 

 the yearly supply of lime from the rivers. 

 He concludes that 36^5 millions of years 

 would be required to produce the whole of 

 this system. 



All these data have been subjected to a 

 criticism by Sollas and compared with one 

 another. Obviously the highest estimates 

 are only limits, and in considering this, 

 Sollas arrives at the general average of 

 about 20-40 millions of years. He points 

 out that the epochs which have served as 

 starting points are not very far distant 

 from one another, considered in a geolog- 

 ical way, and that therefore they may be 

 taken together to delineate the duration 

 of organic life on this earth. 



As we have seen, this duration is by far 

 too short to allow the slow and gradual 

 development of life supposed by Darwin. 

 It necessitates a very substantial abbrevia- 

 tion of this process and thus affords one of 

 the best supports of the theory of mutations. 



Thus we see that this theory is based on 

 almost all the branches of natural science. 

 All of them join in the assertion that the 

 hypothesis of slow and almost invisible 

 changes is too improbable to be accepted 

 and is even in open contradiction to some 

 of the best results of other sciences. The 

 theory of an evolution by leaps and jumps 

 evades all these objections and thereby 

 releases the theory of Darwin from its 

 separate position. 



But it is doing more than this. By 

 rejecting the hypothesis of invisible 

 changes it leads us to search for the 

 visible alterations, which it assumes to be 

 the leaps and jumps by which animal and 

 vegetable species are being produced. If 

 the transformation of one species into an- 

 other is a visible process, it must evidently 

 be sought for and be brought to light in 

 order to study its laws, and to derive from 

 this study an experimental proof for the 

 theory of evolution. 



However, it is hardly probable that these 

 jumps are numerous in nature as it now 

 surrounds us. On the contrary, they must 

 rather be rare, since nobody had seen them 

 until now in the field. Therefore I have 

 sought for a plant which would produce 

 more of such mutations than other plants, 

 I have studied over a hundred species, 

 investigating their progeny, and among 

 them one has answered my hopes. This is 

 the evening primrose of Lamarck, which 

 chances to bear the name of the founder of 

 the theory of evolution which it is pre- 

 pared to support. It is a species which 

 grew wild in the territory of the United 

 States, where it has been collected by the 

 well-known traveler and botanist Michaus, 

 and whence Lamarck derived the authentic 

 specimen for his description. Since that 

 time it has spread in Europe and is now 

 found especially in England, Belgium and 

 Holland in a number of localities, some of 

 which consist of many thousands of indi- 

 viduals. In more than one of these local- 

 ities it has been observed to produce muta- 

 tions, especially in a field near Hilversum 

 in Holland, whence I have obtained the 

 individuals and seeds which have served 

 as the starting points of my cultures. 



In these cultures the species is seen to be 

 very pure and uniform in the large major- 

 ity of its offspring, but to produce on an 

 average one or two aberrant forms in every 



