400 H. B. POLLARD, 



It follows that in the nerves as in the muscles JPolypterus forms 

 a link between the Selachii and Amphibia. Furthermore by this com- 

 parison much light is thrown on the nerves of higher animals including 

 man. The Gasserian ganglion must be considered as resulting from 

 the fusion of 2 ganglia, the Neben- and Hauptgau glia of von Plessen 

 and Rabinovicz , the one being Facial and the second Trigeminal 

 probably also containing the profundus ganglion. Also, the supjwsed 

 ophthalmicus and maxillaris superior of the Trige- 

 minal are really Facial for the greatest part — that is to 

 say in their phylogenetic history. 



Primordial Cranium (figs. 9, 10, 11 etc.). 



Although the description of the skull by Traquair is clear and 

 in general accurate yet there is one important point which he failed 

 to see and another which was incorrect as well as a few details in 

 which his description is not perfectly satisfactory. I have therefore 

 ventured to give a figure of the primordial cranium from above. It 

 was reconstructed from sections 35 ^i in thickness of my smallest 

 specimen, 21 cm in length. All the sections were studied carefully 

 and then about 1 in 8 drawn with the embryograph with a magni- 

 fication of 9. From the drawings by measurement the reconstruction 

 was made. In one or two points only where the sections were not 

 satisfactory owing to the difficulty of cutting, comparison was necessary 

 with another specimen. 



The first point is the persistence of a small sheet (figs. 11, 30) of 

 cartilage partially roofing over the supracranial fontanelle. It may 

 be regarded as indicating the former existence of a complete cartila- 

 laginous tegmen cranii which has become unnecessary by the great 

 development of the frontal bones and their adequate support by the 

 orbitosphenoids. As it is at present it can have no functional im- 

 portance and is merely a rudimentary structure. 



The second point concerns the snout. There is no ossification 

 of the cartilage in front of the nasal septum. The form of the carti- 

 lage in this region is very important. Behind the nasal opening is 

 a slight forward projection which tends to become separate. Where 

 the upper and lower cartilaginous edges of the nasal opening meet 

 in parts there is a slight projection becoming somewhat larger in the 

 older specimen. It lies just at the base of the tentacle. The carti- 

 lage of the snout ends terminall)' as two horizontal ledges above and 

 below the mucous canal enclosed in the dermal ethmoid. The upper 



