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XV. The Croonian Lecture. — On the Structure and Development of the Skull in 
the Lacertilia. 
Part I.— Oil the Skull of the Common Lizards (Lacerta agilis, L. viridis, and 
Zootoca vivipara). 
By William Kitchen Parker, F.R.S. 
Received October 18,—Read December 19, 1878. 
[Plates 37-45.] 
Whilst the last paper, that on the Skull of the Snake, has been passing through the 
press, I have been engaged in working out the skull of the Common Lizards; hence 
the likeness and unlikeness of the two kinds has been clearly before my eyes. 
I consider these small, modern , old-world “ Lacertilia ” to be the kinds in which the 
Lacertian specialization has been carried to its fullest development, and that an 
exhaustive account of their cranio-facial skeleton, its structure and its growth, may 
serve as a sort of practical rule or norma by which to measure that which is typical, or 
aberrant, in the skull of other types of the Lacertilia. 
Besides this piece of work on my selected pattern form, I have to offer to the Boyal 
Society a lesser paper on the skull of one of the lowest and most aberrant of the 
“Families,” namely, the “ Chamseleonidae.” 
This I have worked out in the ripe embryo and adult of the common species, and 
in the adult of the Dwarf Chamseleon—one of the outliers of the Family. 
But in Lacerta I am able to give seven stages of the unborn embryo, besides the 
adult; and six of these stages I owe to the kindness of Dr. Max Braun, of Wlirzburg ; 
the specimens of Zootoca vivipara I owe to Professor Rupert Jones, F.R.S.; and the 
Green Lizard to Professor Alfred Garrod, F.R.S. 
The accumulation, during many years, of “ old experience,” and the slow training I 
have had in delicacy of touch and sharpness of sight, have only barely served me in 
the present piece of work; even the adult skull, in so small a kind, has to be worked 
out with the greatest pains and patience, and asks for several weeks of continued 
labour. 
In the embryos, however, I have had to handle the smallest and softest little 
Vertebrate “Worms:” these I have split, carved, and sliced, so as to reveal many 
embryological facts of great importance, and by these I have been enabled to follow 
