The Pineal Region in Teleosts. 



329 



mobranchs, the velum consists of a simple reduplication of the 

 epithelium of the brain-roof. Such a velum is found in Opsanus 

 at an earlier period of development and persists as the transverse 

 fold of the present stage (fig. 6, VL). The median lobe, although 

 constituting the greater part of the velum at this time, is a second- 

 ary modification of the middle part of the fold. The latter, fol- 

 lowed anteriorly, goes over into the paraphysis, posteriorly into 

 the post- velar arch. On either side, a prominent sagittal ridge 

 of the fore-brain roof can be seen extending backward within the 



VL VM 



Fig. 6. Section no. 97 of the same series as fig. 3. X 97. 



ventricle to the intermediate tubercle (figs. 3, 5). It marks the 

 lateral extent both of the velum and paraphysis. Regarding 

 the contour of the median lobe, one finds the surface broken by 

 fissures of greater or less depth, dividing the whole mass into 

 lobules. The part of the lobe lying behind the level of the pedicle 

 is greater than that anterior. It will be seen by referring to fig. 

 2, that the lobe projects some distance caudad beneath the post- 

 velar arch. The velum, even at this early stage, affords evidence 

 of being adapted to a secretory function. Sections of the lobe 

 show a peripheral thick epithelial tunic, thrown into folds and sup- 



