THE ENERGY OF LIFE EVOLUTION. 789 



yet formulated by the botanist ; again, when the winters are mild and 

 the soil deep, it often shoots up rapidly, only to be snapped asunder 

 by winds of moderate strength. Eucalyptus plantations, moreover, 

 are very costly. If the ground is watery, it has to be drained, other- 

 wise the roots rot ; if the ground is heavy, trenches must be dug in it 

 to make room for the long roots of the trees, and often these trenches 

 have to be drained, as is done in the case of olives, in order to prevent 

 the filtration water from stagnating and the roots from rotting. Hy- 

 draulic amelioration must have recourse to means less uncertain ; and 

 should the conditions of any locality counsel a trial of an absorbent 

 plantation, it should be done with trees of our own hemisphere. The 

 expense is smaller, and the trees are sure not to die. 



At best, hydraulic amelioration is never certain, because the slight 

 humidity of the soil necessary to develop malaria may easily be re- 

 stored to it, even during the warm season. Combination of atmos- 

 pheric with hydraulic amelioration has therefore been tried : to with- 

 draw, that is to say, the humidity from the soil, while at the same time 

 preventing the direct contact of the air with its malarious strata. 

 Leaving the soil with layers of sound earth spread over it either allu- 

 vially or by the hand of man, and also draining the soil itself, was last 

 year, at the instance of Dr. Tommasi-Crudeli, practiced on the grounds 

 of the Janiculan Hill, near the Palazzo Salviati, in the Lungara. The 

 entire area, having been thoroughly well drained and then covered 

 with a dense coating of meadow soil in all those places which could 

 not be paved with street rubble, has since remained without a single 

 case of fever in the numerous personnel of the Military College occupy- 

 ing the Palazzo Salviati, while in the Palazzo Corsini, on the same 

 side of the Lungara, but looking on the grounds of the Janiculan 

 which are still exposed to the air and sun, there have within the same 

 period been not a few cases of fever, some of them fatal. 



-+++- 



THE ENEKGY OF LIFE EVOLUTION, AND HOW IT 



HAS ACTED. 



By Professor EDWAED D. COPE. 



HAVING pointed out in a previous essay the lines of descent of 

 vertebrata which have been brought to light by paleontological 

 investigation, I propose to produce in the present article some evidence 

 as to the nature of the forces which have been actively at work in 

 effecting those changes of structure which constitute the evolution of 

 one type of animal from another. We can obtain this evidence by 

 comparing the successive steps of each line with one another. We 

 thus learn the nature of the modifications, and can, as the case may be, 



