The Pineal Region in Teleosts. 331 



Lepidosteus. In a word, there is no differentiation of this part of 

 the diencephahc roof; it resembles the simple post-velar arch, 

 found by Minot in Acanthias embryos. The vascularity of the 

 dorsal sac and of the region around it was observed by Balfour 

 ('77) and has been described by subsequent investigators. Blood 

 sinuses of considerable size are present in Opsanus in the mesen- 

 chyma dorsad of the post-velar arch, and are connected with the 

 vessels of the epiphysis and velum. 



Paraphysis. (Fig. 2, P). Gaupp's ('97) and Studnicka's 

 ('05) reviews of the extensive literature of the pineal region con- 

 tain few references to the paraphj^sis in teleosts. The question of 

 its presence in the class has received little attention. Three years 

 after Selenka's ('90) discovery of the organ, Burckhardt found a 

 paraphyseal rudiment in the trout. Later, Studnicka ('95) 

 described a paraphysis in two teleosts, Lophius and Anguilla. 

 In adult Lophius the paraphysis appears as an evagination of 

 the brain wall in front of the velum. Its occurrence is not con- 

 stant. In young Anguilla the organ is a relatively large, thin- 

 walled sac connected by a narrow base with the brain. In 1905 

 the same investigator described the paraphysis in two other bony 

 fishes, Cepola rubescens, in which it appears as a conical sac 

 in front of the velum, and Belone acus, where a rudimentary para- 

 physis is indicated by uneveness of the lamina supraneuroporica. 

 The paraphysis of Opsanus is a simple transverse fold of the roof 

 of the telencephalon just anterior to the velum (fig. 1, P). Its 

 walls are composed of an epithelium differing markedly in its 

 greater thickness and staining properties from the tela of the 

 fore-brain. In sagittal sections the paraphysis appears tent- 

 shaped, with an anterior oblique and a posterior perpendicular 

 wall going over into the velar fold. Of these two walls the anter- 

 ior is so newhat thicker. Followed in the lateral direction the 

 the organ is clearly defined to the same extent as the velar fold, 

 that is, as far as the sagittal ridge of the fore-brain roof, described 

 on p. 329. The simple cavity of the paraphysis presents no diver- 

 ticula and communicates freely with the telencephalic ventricle. 



