174 COMPARATIVE MORPHOLOGY OF VERTEBRATES 
the lateralis nerves being lost, while, as stated above, the motor por- 
tions are increased in the mammals, in correlation with the greater 
development of the facial muscles. 
Fic. 172.—Ventral view of brain and cranial nerves of Iguana, after Fischer. J-—XII, 
cranial nerves; 1-3, first three cervical nerves; gp, petrosal ganglion; 7, Jacobson’s commis- 
sure; #, hypoglossal; , nasalis ramus of V; 7/, ramus frontalis of V; sy, sympathetic. 
VIII. The Acustic (Auditory) Nerve is closely associated with the 
seventh, but microscopic analysis shows that it has its own roots and 
ganglion. It is purely sensory, its branches going to the sensory areas 
of the inner ear. Its connections inside the brain and the development 
of the ear itself (see sense organs) show that the nerve belongs to the 
lateralis system, the ear being a group of modified lateral line organs. 
Beyond the ganglion the nerve divides into a vestibular branch, 
supplying the utriculus and semicircular canals, and a cochlear branch, 
going to the lagena and to its homologue in the mammals, the cochlea. 
