On the Anatomy atod t*hylogenetic Position ot Polypterus. 42t 



canal is shown on both sides, opening on the left into the utricular 

 cavity. * marks the spot where the stapes of Urodele arises. 



Fig. 25. Section through the posterior part of the auditory laby- 

 rinth slightly anterior to 24. The relations of the brain to the auditory 

 organ are shown. The notochord has nearly reached its termination. 



Fig. 26. Section through the widest part of the cranial and audi- 

 tory cavity. 



Fig. 27. Section through spiracle, hyomandibular articulation and 

 parasphenoid at its greatest extent. The first branchial artery and 

 that from the precardiac aorta have met in the parasphenoid and fused 

 to form the ophthalmic artery. Round the hyomandibular articulation 

 the cartilage is considerably calcified. Internally is seen the cavity 

 for the ampullae of the anterior vertical and horizontal semicircular 

 canals. 



Fig. 28. Section through the posterior edge of the frontal, the 

 anterior semicircular canal, the exit of the Trigeminus, and the pituitary 

 space. The Abducens nerve has left the basicranial cartilage and runs 

 below the root of the Trigeminus which is shown best on the left side. 

 Only the posterior portion is seen in this section. It is seen not to be 

 surrounded by bone. In a portion of the parasphenoid lies the palatine 

 ganglion and the ophthalmic artery. On the right side the jugular vein 

 does not yet accompany the anterior facial branch of the Vllth but on 

 the left it does. In this section it is shown also how the metapterygoid 

 is independent of cartilage. The pituitary space is roofed over by the 

 posterior prolongation of the orbitosphenoid. Through the anterior semi- 

 circular passage runs on the left side the Ramus oticus to the mucous 

 canal above. 



Fig. 29. Section through sphenotics , posterior end of orbitosphe- 

 noid and ophthalmicus profundus ganglion. On the left side the 

 sphenotic has quite separated from the skull. The orbitosphenoid is 

 interrupted on the left for the ophthalmicus profundus nerve. The Ra- 

 mus ophthalmicus superficialis has quite separated from the Ramus buc- 

 calis. On the right side the ectopterygoid is just appearing. 



Fig. 30. Section through the orbital region showing especially the 

 relation of the temporal and pterygoid muscles, the form of the brain 

 cavit}^ and above all the remmant of the tegmen cranii. The pai^tial 

 invasion of the orbitosphenoid by a process from the parietal is indi- 

 cated by the colouring. On the left side the separation of the post- 

 orbital mucous canal is shown. 



Fig. 31. More anterior section through the region of the pineal 

 gland showing the variation in shape of the orbitosphenoid and how it 

 is invaded by the frontal. 



Fig. 32. Section through the eyes. The roof of the cranial cavity 

 is completed by cartilage. 



Fig. 33. The following 3 sections are taken from another better 

 preserved specimen. The magnification is 12 linear. The ethmopalatine 

 articulation with the form of the bones taking part in it is shown. 

 The anterior edge of the eye is cut. In the nasal capsule lies the nose 



