Johnston, Forehrain Vesicle in Vertebrates. 529 



impulses. Neither of these important forehrain centers is provided 

 with the means of carrying on any function. 



As a further indication that the primitive forehrain has some func- 

 tions in addition to the olfactory sense, the writer has described two 

 ascending tracts to the forehrain. One of these, the tractus loho- 

 epistriaticus, is believed to carry up gustatory impulses to the 

 epistriatum from the tertiary gustatory center in the hypothalamus 

 (fishes and amphibia 1898, 1901, 1902, 1906). If this hypothesis 

 is correct the epistriatum must be regarded as a correlating center 

 for smell and taste and so a forerunner of the smell-taste cortex. 

 A second tract has been traced in Acipenser (1901) from the 

 tectum opticum only as far forward as the optic chiasma where it 

 enters the telencephalon. A\Tiether it ends in the corpus striatum 

 or in some other i^art of the forehrain remains to be seen. In my 

 textbook (1906, p. 336) I have pointed out that the entrance of 

 such a tract as this into the telencephalon constitutes evidence of the 

 beginning of the correlating centers which in higher vertebrates we 

 call the neopallium. The writer has been convinced for some years 

 that the elements or beginnings of all the chief parts of the telen- 

 cephalon of mammals and man are to be found in the telencephalon 

 of primitive vertebrates. 



Herrick's revision of the nomenclature of the diencephalon and 

 mesencephalon contains two new terms, ophthalmencephalon, and 

 medithalamus. As a pedogogic term based on function, "ophthalm- 

 encephalon" has my hearty approval. xVs a morphological sub- 

 division of the brain it is open to the objection that the regions 

 included — retina, chiasma, lateral geniculate bodies, pulvinar and 

 tectum opticum — do not have sufficient morphological unity. The 

 term medithalamus is offered by Herriek provisionally for the things 

 left over after the ophthalmencephalon has been set apart. It thus in- 

 cludes the central gray and a number of nuclei of diverse func- 

 tions. The fact that it must include the medial geniculate body on 

 the lateral surface of the diencephalon seems to the Avriter a fatal 

 objection to the tenn medithalamus. 



In the diencephalon the epithalamus and hypothalamus are fairly 

 clearly marked both functionally and morphologically. The hypo- 



