Herrick, Morphology of Brain of Bony Fishes. 341^ 



unlike all other nerves, in the earliest stages consists through- 

 out their entire extent of nucleated bundles of the finest 

 parallel fibrils, which bundles I compared with the axis- 

 cylinders of other nerves. From this circumstance I con- 

 cluded that these nuclei .correspond to the nuclei of nerve 

 cells, and that a nucleated sheath of Schwann accordingly is 

 not present, although it has been assumed by all authors since 

 Max Schultze. If this were correct, then the olfactory fibres 

 consist of bipolar nerve cells, which either each sends a pro- 

 cess peripherad, or, as seemed to me probable, are united in 

 moniliform series, as must be assumed in the sympathic; in 

 this case the nerve grows by successive subdivision of the 

 nucleated portions without complete separation of the result- 

 ing segments. 



" In any case the development of such a nerve from the 

 central nervous system is difficult to explain from any exist- 

 ing analogy, and it afforded a very desirable solution of the 

 matter when His, a short time since, announced that the 

 olfactory does not develop from the olfactory lobe, but rather 

 takes its origin from the epithelium of the olfactory pits, and 

 grows in the centripetal direction, like the cells of the spinal 

 ganglion. This investigation of His I have recently verified 

 with the following results: 



" In the earliest stages the olfactory pits have no nerves, 

 and are not connected with the olfactory lobe. In an embryo 

 chick of four days there is a slight proliferation of the epi- 

 thelium of the olfactory at the end nearest the brain only, 

 forming a bundle .030-.054 millim. thick, which can be 

 followed to the outer margin of the hemisphere without 

 entering into any connection therewith. The bundle is 

 finely fibrous and nucleated, and exhibits on its surface fusi- 

 form cells." 



Prof. Kolliker records similar observations upon mammals 

 and concludes: 



" I consider the assumption made by His as very prob- 

 able, and may add that when the olfactory nerve has once 



