Amphibians, Pioneers of Terrestrial 
Breeding Habits * 
By Coteman J. Goin 
Professor of Biological Sciences, University of Florida, and 
Research Associate, Carnegie Museum, Pittsburgh 
ANY TEACHER of comparative vertebrate anatomy who is worth his 
salt does, I am sure, emphasize the anatomical adaptations necessary 
for the invasion of land by the vertebrates. This aspect of evolution 
has been thoroughly explored, and within the limits of the paleon- 
tological record and the philosophical insight of man has been rather 
adequately explained. Another facet of the development of life on 
land is that of the environmental conditions under which these 
adaptations arose. These, too, have been investigated, and there has 
been in recent years a flurry of papers (Orton, 1954; Ewer, 1955; 
Gunter, 1956; Inger, 1957; Romer, 1958) discussing the ecological 
aspects of adaptation to life on land, in one of which the present 
writer had a hand (Goin and Goin, 1956). There remains another 
adaptational aspect, however, which I think has been neglected, and 
that is the development of those reproductive devices necessary to life 
on land. True, most elementary texts state that the final break with 
the water was made possible through the development of the shelled 
reptilian egg in which the embryo is enclosed in a fluid-filled sac by a 
new membrane, the amnion. They usually do not pursue the subject 
further unless it be simply to imply that the shelled egg made neces- 
sary internal fertilization. In fact, it is difficult even to find a litera- 
ture reference to the idea that it must have been the other way 
around—that is, that internal fertilization made possible the develop- 
ment of the shelled egg. 
It is this subject of the adaptive aspects of life history among the 
first terrestrial vertebrates that I want to pursue here. Surely we 
must not assume that only a single evolutionary attempt was made to 
1Read at the 38th annual banquet of the American Society of Ichthyologists and Her- 
petologists. In preparing this paper, the author has greatly profited from discussions with 
others. He would like to mention especially Dr. Leonard P. Schultz, Dr. Ernest Lachner, 
Dr. Robert Inger, Dr. M. Graham Netting, Dr. Kenneth W. Cooper, and most particularly 
his wife, Olive Bown Goin. 
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