1833.] On Progressive Development, &c. 465 
“II.-—On Progressive Development in the cold-bloodedVertebrata. By D.W. 
Nash, Asst. Surgeon, Beng. Est. A. L. S. Corresp. Member S. A. 
Among the many important considerations embraced by the theore- 
tical department of geological science, the question of the gradual 
transition of fossil remains in the strata which form the crust of our 
globe,—the supposed development of the forms of organic life in a 
progressive and ascending series,—and the application by analogy of 
this hypothesis founded on actual observations of that which has been, 
to the phenomena which are daily recognized in the present state of 
things,—are subjects of the greatest interest to the geologist and natu- 
ralist, while to the cause of science in general their elucidation is of 
considerable importance. 
On these questions the most eminent authorities among modern 
geologists are divided, and though not perhaps so violent in the expres- 
sion of their opinions as the Neptunists and Plutonists of a former 
day, the advocates and opponents of the theory of progressive develop- 
ment have entered with no little warmth into this interesting contro- 
versy. 
Mr. Lye tt in his Principles of Geology, in speaking of the conclu- 
sions arrived at by Sir H. Davy from the consideration of geological 
data, expressly states, that, ‘‘ the theory of progressive development 
of organic life from the simplest to the most complicated forms, has 
no foundation in fact.” 
On the other hand many observers equally high in scientific 
reputation have imagined that they see, not only in the fossil monu- 
ments of former worlds, the imperishable evidences of a state of 
things differing from, and antecedent to, that now under our observa- 
tion,—but also in the organization of the present inhabitants of our 
globe, indisputable proofs of a progressive advance to perfection in the 
forms of organic life. 
It cannot be denied that the fossil remains which have been observed 
in the different strata of the earth’s crust, are arranged very nearly 
in the order which the animals to whom they belonged, occupy in the 
natural system of zoology ;—that those genera which zoologists are 
agreed in considering as the least developed forms are found in the 
lowest or most ancient formations, and that, as we ascend from the 
primitive through the transition, secondary, and tertiary rocks, new 
and more perfect forms of life meet us at every step of the investiga- 
tion. 
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