100 FREDERICK TILXKY AXD LUTHER F. \VARREN 



Differences observed in the epi/thi/xeal coi///>lc.r in Utc mrious 

 species <>f tdeosts alrcadi/ investigated 



PHYSOSTOMI 



1. Kxi'.r ///r///.s. (iottsche ('3"))' ;i1 mentioned for the first time 

 the pineal organ in this form. Stieda 378 in 1873 called it a red 

 body of very insignificant size. Cattie'' in 1SS2 distinguished 

 .-in end- vesicle and a stalk, the former richly supplied with 

 blood and deeply sunken into a fossa in the roof of the skull. 

 He described oval ependymal cells, and pear-shaped cells in 

 the end- vesicle. The stalk was hollow and its dorsal wall con- 

 tained a tractus pinealis. There were many folds in the end- 

 vesicle. 



2. Tinea rnl'jaris. Cattie ('82). fi In this form there is a 

 well-defined proximal portion, which, however, is a fine strand- 

 like structure. The end-vesicle is flattened and much expanded. 



3. Sal mo salar. Cattie ('82). r ' This species has an end- 

 vesicle which is pear-shaped and a very short, highly vascular 

 stalk. The end-vesicle is in contact with the roof of the skull. 



4. Salmo fario, pnrpuratus and fontinalis. Rabl-Riickhard 

 ('83) ; 319 Hill ('94). 18 These forms present a pineal organ hav- 

 ing an end-vesicle in a depression of the skull and a stalk con- 

 necting it with the posterior commissure. The stalk has a cen- 

 tral canal, the lumen of which is bounded by cylindrical cells. 

 Hill found in embryos not only the pineal organ, but the para- 

 pineal organ as well; the latter remains rudimentary. Hill 

 called the pineal organ the posterior epiphysis. It presents a 

 proximal, narrow portion and a distal, flattened end-vesicle 

 which is thick and lodged in a deep fossa of the skull. It has 

 many diverticula and is rich in blood vessels. A long canal 

 runs through the stalk; nerve fibers connecting with sonic of 

 these cells in the end-vesicle make their way through a portion 

 of the stalk, and a definite tractus pinealis in the dorsal wall of 

 the stalk ends in the posterior commissure. In the adult of two 

 years old, Hill described a, distal end-sac which retains the em- 

 bryonic form. The rest disappears. In the distal part of the 

 BBC are many cell groups containing granular or colloid masses 



