152 CHAKLES E. STOCKARD AND A. L. JOHNSON 



ferent morphologic types will be considered from these stand- 

 points. 



It is intended at this point to present the contrasts in 

 morphologic characters as shown among the dog skulls, and 

 to consider the mode of hereditary transmission of these 

 characters and the developmental reactions involved in their 

 expression. It is safe to say that the skulls of no other single 

 mammalian species can approach in variety the series derived 

 from the domestic breeds of dogs. Starting with those having 

 long narrow crania, a high sagittal bony crest and a long, 

 projecting, strongly developed facial skeleton largely formed 

 by ferocious jaws, we may pass to the opposite extremes 

 showing almost spherical crania with smoothly rounded or 

 flattened tops and no trace of the sagittal crest, and with a 

 rounded forehead overhanging a facial skeleton with defective 

 jaws reduced to such an extent as not to project beyond the 

 bulge of the forehead, and with practically no dental occlusion. 

 The face in such a skull is as flat as that shown by the apes 

 or even man (see figs. 7 and 8, pi. 50, p. 275). Between these 

 extremes almost every variation and deviation can be dem- 

 onstrated in our collection of about 1000 pedigreed specimens. 



The Normal or Standard Dog Skull 



It is not difficult to agree on the type of skull which one 

 could accept as ancestral or normal for the dog. Several 

 dog breeds still possess skulls resembling much more closely 

 those of the wolf or wild Canidae than of numerous other 

 dog breeds. In other words, in spite of the large variety 

 of skull patterns and the extreme deviations they present, 

 many breeds still retain the normal or standard typed skulls 

 from which these modifications must have arisen. This is of 

 great advantage to the investigator since it enables him to 

 determine the exact kind and degree of the alterations oc- 

 curring" in a number of different regions and structures of 

 the skull. The ancestral form is often lost or obliterated in 

 many animal groups which have deviated widely from the 



