376 J. B, JOHNSTON 



His in his Allgemeine Morphologie in 1892 (p. 349, 352) defined 

 the lamina terminahs as the frontal portion of the frontal seam 

 of closure. Below, the lamina terminalis ends in the recessus 

 opticus (rec. praeopticus) and is followed by a basal portion of 

 the frontal seam containing the optic chiasma. The upper bor- 

 der of the lamina terminalis in human embryos is marked by 

 an inward fold (i.e., the velum trans versum) in early stages and 

 later by the beginning of the choroid plexus. Within the lamina 

 terminalis as thus defined (cf. p. 349 and 352) in many animals 

 lies the neuropore. 



Von Kupffer ('93) described the neuropore in the sturgeon 

 under the name of lobus olfactorius impar. Von Kupffer's mate- 

 rial was unfortunate because the eversion of the pallial part of 

 the telencephalon in ganoids leaves the recessus neuroporicus 

 apparently bounded dorsally by a non-nervous membrane only. 

 Comparison of v. Kupffer's figure 18 with the writer's figure of 

 this region in the adult sturgeon brain ('11 b, fig. 52) will show 

 that there intervenes between the locus of the recessus neu- 

 roporicus and the plexus chorioideus a membrane which is 

 distinctly thicker than the choroid plexus and differs from it 

 histologically, v. Kupffer ('94) also described the recessus 

 neuroporicus in Petromyzon and it has since been shown by 

 Sterzi ('07) that this lies below the dorsal telencephalic commis- 

 sure. Upon direct comparison of the adult human brain with 

 that of the sturgeon embryo, v. Kupffer believed (p. 39) the 

 recessus triangularis of Schwalbe ('81) to be the homologue of 

 his lobus olfactorius impar. 



In the comments made by His ('93) upon v. Kupffer's work, 

 he identified v. Kupffer's lobus olfactorius impar with the an- 

 gulus tenninalis of His. This angulus terminalis is the meeting 

 point of the tela chorioidea with the dorsal border of the lamina 

 terminalis as defined in 1892. This does not agree with v. 

 Kupffer's view cited above, nor does it agree with His's own 

 statement in 1892 that the neuropore lies within the lamina 

 terminalis. 



Burckhardt ('94 b) identified v. Kupffer's lobus olfactorius im- 

 par with a recess in reptiles situated at the point of junction of 



