AMPHIBIANS. 63 



Example 2. Lissotriton punctatus, Latreille. 



I am able to give several stages of the Common Smooth Newt ; the youngest of these was 

 five and a half lines in length, and an external view of the left moiety of the Shoulder-girdle of 

 this larva is shown in Plate III, fig. 7, magnified forty diameters. 



Every essential part of the Shoulder-girdle is to be seen in this early stage, which represents 

 the permanent condition of the Proteus ; for the Sternum is not distinguishable in the delicate 

 blastema forming the lower edges of the ventral laminae. 



The supra-scapula (s. sc.) is fan-shaped, and the handle-like part passes insensibly into the 

 narrow scapula (sc.) which is already ensheathed by a delicate, corrugated ectosteal layer. The 

 cartilage-cells of the scapular region are evidently entirely unaffected at present by the bony film 

 which invests them. The rest of this plate of frail, young cartilage, is free from bony invest- 

 ment ; the nerve-passage is very clearly displayed ; and the coracoid notch is large and semicir- 

 cular ; the prse-coracoid (p. cr.) is a mere bud ; and the epicoracoid (e. cr.) is a sickle-shaped bar. 

 The glenoid cavity is a large wavy-sided triangle ; and the proximal part of the humerus, the 

 bony shaft of which has appeared, is seen in its place. 



In another specimen of Lissotriton punctatus, nearly twice the length of the last, (ten lines), 

 and the figures of which are magnified thirty diameters, great changes of form have taken place, 

 and the Sternum is to be seen. The characteristic height of the supra-scapula (Plate III, fig. 8, 

 s. sc.) is now shown ; and the sheathing by a thin corrugated bony plate of three-fourths of the 

 scapular region (sc.) The budding prae-coracoid (p. cr.) has become longer, but is still relatively 

 short and narrow ; the glenoid cavity (gl.) has acquired more perfect lips. The epicoracoid region 

 (e. cr.) has spread in all directions, and is fast approaching the mid-line below ; the notch has 

 become narrow, and the nerve-passage has a large space of cartilage between it and the notch : 

 no bone has appeared, except that which enrings the scapula. 



The Sternum (Plate III, fig. 8, st.) can now be seen, but its cells are much younger than those 

 which form the mass of the Shoulder-plate ; and the left margin is merely a somewhat consistent 

 band of granular blastema. The form is that of an equilateral triangle, but the base behind 

 is produced, and not notched as in the Axolotl. I have not been able to find a primordial fissure 

 along the mid-line of the Sternum in any Urodelous Amphibian ; but in all the true Salamanders, 

 even in the adult, the anterior margin is obliquely split for some distance. It is quite probable 

 that the great priority of development of the moieties of the Shoulder-girdle, their huge relative 

 size, and the great extent to which they overlap, may bias the growth of the tardier, and feebler, 

 correlated sternal plate. I shall, without going out of my way, subsequently show some clear 

 instances of unsymmetry in the right and left halves of the Sternum in the Warm-blooded Classes ; 

 and it is quite possible, and even probable, that one half of the very primordial Sternum of a 

 Salamander may get the start of and overreach the other. 



The next stage is that of a Lissotriton punctatus one inch and eight lines in length ; the figure 

 (Plate III, fig. 13), shows the inside of the right moiety of the Shoulder-plate; part of the left 

 moiety; and the Sternum, magnified twelve diameters. The parts are drawn from each other, 

 for they are very loosely attached, but the epicoracoids naturally lie in the sternal grooves, and 

 overlap each other. 



