THE GENETIC RELATIONS OF THE CETACEANS. 25 
even if the facts do not appeal to the senses of another in like 
manner, still do I prefer to trust to my own. 
Inferences respecting genetic relations.—The question having been 
raised as to the comparative degrees of differentiation of the ceta- 
ceous types, it may be well to pursue it further. 
Zeuglodonts. As already observed, the Zeuglodonts, in the 
form and structure of the jaws, the character of the teeth (molars 
double-rooted in part), the presence of the typical (Edueabilian) 
number of teeth in the intermaxillary bones, the more or less 
anterior position of the nostrils, the contour of the skull and 
general relations of its constituent elements, and in fact almost 
all the known parts of their organization, differ much less from 
the ordinary mammals than do any of the existing Cetaceans. 
They are therefore the most generalized or the least specialized 
Cetaceans known ; these are simple facts which appeal to the senses. 
As inferences, the forms so distinguished represent, better than 
any other Cetaceans, the primitive ones from which they, as well as 
the latter, have descended. None of the known Zeuglodonts can, 
indeed, be the progenitors of the modern Cetaceans, since types 
closely related to the latter are associated with them in tertiary 
strata, and the known Zeuglodonts may have become much differ- 
entiated (possibly even more than the modern Cetaceans), in some 
minor points, from the primitive forms, but that they are, as a 
whole and in all essential features, more like (and therefore more 
allied to) those ancestral types can scarcely be doubted, me judice. 
Therefore those Zeuglodonts may appropriately be regarded as the 
nearest known representatives of the Protocetacean types, as quasi- 
intermediate forms between the quadruped mammals and the more 
specialized Cetaceans, and in a genealogical system must be repre- 
sented as the nearest of kin to the prototypes of the order. 
But even the few forms of Zeuglodonts known differ in degrees 
of differentiation from the normal mammals, and must be so repre- 
sented, the Basilosauriids representing a more gaeran and 
the Cynoreids a more specialized type. 
Mysticetes. It seems more probable that the agreement of the 
Mysticetes and Denticetes in the attenuated intermaxillaries, 
the anterior nostrils, pectoral members, ete., should be the result 
of inheritance than of independent assumption, and therefore that 
they have developed from forms thus differentiated from the r 
tive Zeuglodont stem. , 
