106 FREDERICK TILNEY AND LUTHER F. WARREN 



Differences observed in the epiphyseal complex in the various 

 species of teleosts already investigated 



PHYSOSTOMI 



1. Esox lucius. Gottsche ('35) 154 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 60 in 1882 distinguished 

 an 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 vulgaris. Cattie ('82). 60 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. Salmo solar. Cattie ('82). 60 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, purpuratus 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 some 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 

 sac are many cell groups containing granular or colloid masses 



