Morphological Studies. 'til 



and in the adult, and correctly describes the columns as made up of 

 ganglion cells, and, as we shall see, quite rightly concludes that the 

 cells of the columns are comparable to the deeper layers of the ol- 

 factory epithelium in the same animal. Hence he supports Leydig's 

 contention that the columns contain ganglionic cells, but he remarks, and 

 in this I cannot agree, that the polygonal form of the columns has 

 been determined by the meshes of the capillary plexus, through which 

 the outgrowths have taken place (34, p. 391). 



As a matter of fact the growth of the columns takes place before 

 the development of the capillary plexus. He concludes, and with this 

 conclusion I agree completely and emphasize it, that Jacobson's organ 

 in Lacertilia and Snakes is a very highly specialized portion of the 

 olfactory epitheUum (p. 393). 



Klein (18, p. 565) has also noticed cells projecting singly or in 

 small groups into the mucosa from the sensory epithelium of Jacob- 

 son's organ of the rabbit. But, so far as I am aware, no observer has 

 traced the development of the columns from the neuro-epithelium, or 

 noticed the exceedingly close correspondence, amounting, as I think, 

 to a complete homology, between the smell buds of the Ophidian Ja- 

 cobson's organ (and their ganglionic columns) and the smell buds of 

 Amphibia and fishes, as described by Blaue (5). There is a very 

 striking resemblance between the former and the smell-buds of Triton 

 cristatus as figured by Blaue (38, Tf. 14, fig. 36). 



Comparison of Jacobson^s Organ in Lacertilia witli tlie same 



structure in Opiiidia. 



The question naturally arises whether or not the sensory epithe- 

 lium of Jacobson's organ in the Lacertilia ever presents the divi- 

 sion into smell-buds and their associated ganglia such as I have just 

 described in the Ophidia. 



A superficial examination of sections of advanced or nearly ripe 

 embryos of Anguis or Lacerta would lead to a negative conclusion. 

 But on closer investigation of good sections, it can be made out that 

 the deeper or ganglionic layers show traces of an imperfect division 

 into ganglionic columns such as we found in the Ophidia. This is 

 most easily seen in the somewhat regular wavy outline of the outer- 

 most ganglionic layers of the organ as seen in section (fig. 9 La- 

 certa, fig. 10 Anguis). 



This wavy outline and the arrangement of the ganglionic cells in 



Zool. Jahib. HI. Ablli. f. .Vluiph. 5]_ 



