522 'Journal of Comparative Neurology and Psychology. 



hypothalamus and Kappers (190G, 1908) has recognized this tract 

 also in selachians. I have interpreted this as an ascending gusta- 

 tory tract (1906, p. 304). The center into which the tract enters 

 at first (Petromyzon) receives secondary olfactory fibers, but in 

 most fishes, especially the selachians in which the olfactory appa- 

 ratus is highly developed, receives tertiary fibers as well. The 

 entrance of an ascending, presumably gustatory tract, into a ter- 

 tiary olfactory center in fishes creates a condition analogous to 

 that found in the general cortex of mammals ; namely, a center serv- 

 ing for the correlation of two sorts of sense impressions which are 

 received over neurone chains of three links. We seem, therefore, 

 to have in the so-called epistriatum of fishes a primitive olfactory 

 cortex. The gray matter does not consist of superficial layers of 

 cells, but forms part of the wall of the ventricle. 



This primitive epistriatum, as seen in Petromyzon and Selachians, 

 is not all accounted for in the history of what Edinger and Kappers 

 call the epistriatum in higher forms. The primitive epistriatum 

 lies in the side wall (floor and roof) of the selachian forebrain 

 (Kappers). The fiber connections which I have worked out in the 

 gi'eatest detail in Petromyzon and Acipenser, show that the epistri- 

 atal formation in the side wall continues caudad to the border of the 

 diencephalon, i. e., nearly to the nucleus habenulas. This is the region 

 called by Kappers the dorsal part of the prsethalamus. That this is 

 telencephalic territory is readily shown by the fact that the velum 

 transversum is attached to the lateral wall of the brain just in front of 

 the ganglion habenulse and behind the peculiar structure here being- 

 considered. The primitive epistriatum therefore consists of (1) a 

 dorsal or roof portion, (2) an epistriatum in the narrow sense resting 

 upon the striatum (pala?ostriatum, Kappers) and (3) a caudal portion 

 forming part of the wall of the median ventricle of the telencephalon. 

 I have shown (1906, Chap. 18) that the caudal portion is of greatest 

 size and importance in Petromyzon, is still of considerable impor- 

 tance in Necturus, and in mammals is represented by a small struc- 

 ture called by older authors the paraphysis but shown by Elliot 

 Smith (1896) to be a nervous structure. The caudal portion de- 

 creases in size and importance in the vertebrate series. The secx)nd 



