602 
ME. W. K. PARKER ON THE STRUCTURE AND 
This is, in itself, a most agreeable part of my work ; and I hasten to sift away all 
that appears now to be untrue, however well winnowed it once appeared. 
The advantages above mentioned are not all, nor even the greatest of those I have of 
late derived from the researches of my valued fellow-labourer ; most suggestive and pro- 
mising are the views which have lately been laid before the Society (Proc. Boy. Soc.Dec.17, 
1874, vol. xxiii. p. 127) on the Amphioxus and its structural relations to the Lamprey, 
its larvse, and its kindred. This short paper is, if I am not greatly mistaken, of almost 
equal value with the ‘Croonian Lecture’; if the author’s deductions stand the test of 
further research, they will light up the darkest recesses of Vertebrate morphology. 
I shall suppose the reader to be familiar with that communication, and it will be 
open to us now to consider the ordinary Vertebrata, or Holocrania, to be highly spe- 
cialized and metamorphosed descendants of long-lost 4 Entomocrania.’ 
In the latter the long, many-jointed skull may be compared to that part of a plant 
in which all the ‘internodes’ are developed; whilst the skull of ordinary Vertebrata 
may be likened to a flower, where the internodes are not developed, and where the 
foliar organs, being brought nigh to each other, coalesce in various ways and undergo 
remarkable modifications of form and of relative size. 
At present I bring forwards corrected figures of the skull of the adult common Frog 
( Pana temporaria), and new results obtained by a study of the development of the 
skull of the common Toad (Bufo vulgaris), correcting, by these observations on equiva- 
lent stages, those which are imperfect or untrue in the first memoir. 
In that paper the figures are seldom inaccurate, but both these and the descriptions 
will be brought now into comparison with these newer results. 
After this has been done, I shall show the structure of the skull in various stages of 
the 4 Aglossal ’ Toads — namely, Bactylethra , the Cape Toad with nailed paws, and Pig) a, 
the remarkable Surinam Toad. 
These will take up all the space available in a single paper ; afterwards, my researches 
on the Bull-frog (Bana pvpiens) and the Paradoxical Frog (Pseudis paradoxa) will, 
with others, be offered to the Society, and, also, as time and opportunity serve, figures 
and descriptions of the less-modified tailed types of Amphibia. 
Such terms as are new in the present paper are adopted from the two memoirs of 
Professor Huxley just referred to; the gradual introduction of accurate morphological 
terms is not only desirable but absolutely necessary, yet these cannot be given before 
the true nature of the parts is understood. 
In the Class of Fishes the specialization of the parts of the skull and face is greatest 
in the Teleostei, and least in the Marsipobranchii ; the Elasmobranchii come nearest 
to the latter, the Ganoids nearest to the former ; all these types of skull must be brought 
into light; of my own work only that on the Teleostean skull has as. yet appeared. 
One thing which misled me in working out the Frog’s skull was the expectation of 
finding its development much more in harmony with that of the Teleostean type than 
it turns out to be. 
