762 Dr. J. BEARD, 



bryonic nerves. That the olfactory nerve in certain stages pos- 

 sesses a ganglionic formation is certain (see fig. 8 Lacerta). 



Perhaps here I may be allowed to state briefly a conclusion of 

 ray work on nerve and sense organ development, leaving its fuller con- 

 sideration for a subsequent occasion. 



In the chain connecting the sensory cells of a Vertebrate sense 

 organ with the central nervous system we may find ganglion cells 

 arising from at least three different morphological sources, apparently 

 from four, but the first and second sources now to be enumerated are 

 morphologically identical, and the sole difference between the two cases 

 rests in the fact whether the ganglia remain in the neuroepithelium or 

 not, — a difference of no morphological importance. 



1) In the neuroepithelium itself; as, for instance, at the bases of 

 the sense cells of nose, eye, ear or of Jacobson's organ of Anguis. 



2) On the inner side, coming to lie beyond the neuroepithelium, 

 but derived developmentally from it : viz., lateral ganglia of the bran- 

 chial or lateral sense organs, bud-like ganglia of Jacobson's organ of 

 Ophidia. 



3) Between the lateral ganglion and the central nervous system : 

 as, for example, the neural ganglia of trigeminus, facial, auditory, or 

 vagus nerves. 



4) As a special difl'erentiation in the central nervous system itself 

 i. e. olfactory lobe &c. 



One or other of these may be ill-developed, or if the fourth be 

 specially developed we may find the first, second, and third almost 

 reduced to nerve elements alone. The phylogenetic meaning of all 

 these complications is something of which we as yet hardly possess 

 any conception; how far a solution of the matter seems possible will 

 be indicated in a subsequent study on the phylogenetic history of the 

 branchial or lateral sense organs. 



If these complications appear startling, they will hardly be so, if 

 we consider, how complicated is the manner in which, according to the 

 epochmaking researches of Kleinenberg (49), the Annelidan nervous 

 system is ontogenetically evolved. Why should we expect the 

 Vertebrate central and peripheral nervous systems to arise in a less 

 ntricate fashion? The Vertebrate central nervous system with the 

 peripheral system is as complicated when compared with that of the 

 Annelid as an important line of railway of to-day is when compared 

 with one of forty years ago. 



