SKULL OF A HUMAN FETUS OF 40 MM. 319 



uity was determined as accurately as possible and the wax plates 

 piled upon a plane adjusted at the proper inclination. It is also 

 to be noted that a few sections passing through the dorsal ex- 

 tremity of the occiput were wanting from the series, and the 

 small portion of the occipital region which they represented has 

 been reconstructed by reference to other models, the parts so 

 added being painted white, so that they may readily be recognized. 



In the following description of the models I have used, as far 

 as possible, the terms which are current in the literature, and 

 when those referring to the human skull were exhausted recourse 

 was had to the terminology in use in the more recent publications 

 upon the chondrocrania of mammals. Preference is given to 

 the BNA, and names not hitherto introduced into human chon- 

 drocraniology are usually followed by the name of the author who 

 has employed them, the ideal being always kept in view of a 

 system of terms uniform throughout the mammalian forms at 

 least. New names, introduced by the writer, are indicated by 

 making their initial appearance in italics. 



An attempt has been made to select such terms of orientation 

 as may be applied to animals having either a horizontal or a 

 vertical long axis. Thus the terms ventral, dorsal, cranial, cau- 

 dal, lateral and medial are generally used, but their respective 

 equivalents for the human figure, such as anterior or front, pos- 

 terior or back, superior or upper, inferior or lower, external or 

 outer, internal or inner, are also employed. Oblique directions 

 are indicated by combinations of the above terms. 



Measurements appearing in the text have been taken from the 

 models, and are thus magnified thirty times. 



THE SKULL AS A WHOLE 



The primitive skull of homo at the 40 mm. stage presents, in 

 general, the characters which have become familiar through 

 the illustrations and descriptions of v. Noorden, Jacoby and 

 Levi for younger embryos, and the model of Hertwig for a more 

 advanced age, combined with several features that are char- 

 acteristic of this period of development. The outline, when the 

 many gaps are filled in, suggests the osseous skull. 



