396 Journal of Comparative Neurology and Psychology. 



2. If in the olfactory epithelium, is there also any indication 

 of a portion of the anlage arising from the brain ? 



3. Do the cells of the so-called anlage become ganglion 

 cells. 



4. If these are ganglion cells, what is their location in the 

 adult nerve ? 



5. If these cells are not ganglion cells, what is their fate 

 and where are the true ganglion cells located ? 



The writer has undertaken to trace the history of the ol- 

 factory nerve in swine, from its first indication onward to the 

 sub-adult stage, and believes that in addition to giving a gen- 

 eral history of its development, he is able to throw some light 

 on all the above questions. But the fate of some of the cells 

 of the so-called primitive anlage remains unsettled. 



The work was undertaken at the suggestion of Professor 

 William A. Locv of the Northwestern University, whom the 

 writer has to thank for much valuable direction. 



Po'sonal Obsefuations. 



Methods. — Perfectly fresh material for fixation was obtained 

 by plunging the embryos, removed from uteri of recently killed 

 swine directly into the fixing fluid. At the time of their removal 

 from the uteri, the hearts of the embryos were still normally 

 beating. 



The most satisfactory results were obtained from material 

 fixed in vom Rath's picro-platin-osmic mixture and stained with 

 iron haematoxylin. Embryos fixed in corrosive-acetic and 

 stained with either Delafield's haematoxylin or iron haema- 

 toxylin gave good results. 



For Golgi preparations the rapid method was used. Some 

 very good results were obtained with Golgi from material that 

 had been preserved in ten percent formalin for a week or more. 



Fonnation of the Olfactory Pit. — Soon after the closure of 

 the neural groove, a thickening, caused by the cells of the ecto- 

 derm becoming elongated, appears well forward upon each side, 

 of the head region. This is the olfactory plate. 



At this time the greatest thickness of the olfactory plate 



