THE YOUNG NATUKALIST. 



109 



retarded development enables the female to economise its vital force and 

 energy, and so increase its power of reprodnction. 



It is a Darwinian axiom, I think, that an organ which is no longer of 

 service, looses its power and becomes more or less rudimentary. Now we 

 often find from experience that a fondly cherished pupa of a good thing, de- 

 velopes a specimen with rudimentary wings, and, after a time, we awake to 

 the mournful fact that they never will grow, from some cause we are not able 

 to determine. Supposing a females able to dispense with wings in propagating 

 its species, and with crippled or partially developed wings, it would have an 

 advantage over other specimens which had dispersed their vital force in de- 

 veloping these delicate organs, propagate a greater number of offspring, with 

 an inherited tendancy this accident of birth, and by that process known as 

 the suvival of the fittest produce a species having apterous females. It is 

 worth noting that all apterous females are very prolific, the species produced 

 rather small, and that the economy of vital force thus effected is a distinct 

 gain. I am sure if entomologists will give their theories and opinions on 

 this subject, if it is not settled to the satisfaction of all, it will at least, leave 

 it in a more satisfactory position. 

 Stoke Newington, London. 



THE GEOLOGY OF KENT. 



By GEO. E. EAST, Junr. 



The inhabitants of Kent have great facilities for the study of the rocks of 

 their county. All along the coast admirable sections are exposed in the 

 cliffs, and inland the absence of the surface deposits, which under the name 

 of drift, so obscure the geology of the counties north of the Thames, per- 

 mit the various strata to be traced with comparative ease. I purpose in these 

 notes, as in my last, simply to mention the formations as they occur, and to 

 give a list of some of the chief fossils. To begin with the oldest rocks which 

 are the : — 



WEALDEN BEDS. — The strata included under this term have a maxi- 

 mum of more than 2,000 feet. They are divided into two beds, viz. the 

 Hastings Beds and Weald Clay. 



THE HASTINGS BEDS. — These are chiefly sandy, and occupy the 

 south of the county. 



THE WEALD CLAY.— This constitutes a low flat tract of land from 

 four to six miles wide ; it is a brown or blue clay, ill drained, and mostly in 

 pasture. 



