THE PINEAL BODY 95 



the pia mater and another from the dura mater. Some authors, 

 .among them Cattle, 60 have described a parietal foramen. In 

 Acanthias vulgar is this opening in the cartilaginous skull appears 

 to be doubled, the two openings being separated by a small, 

 cartilaginous bridge. Neither Studnicka 389 nor Ehlers 108 was able 

 to discover any such openings in the forms which they investi- 

 gated. The parietal cornea is absent and the parietal spot is 

 very infrequently observed. 



Differences observed in the epiphyseal complex of the various 

 species of selachians already investigated. 



ELASMO BRANCHI 



1. Scyllium canicula and calulus. Balfour (78) 10 studying the 

 embryonic development; Owsiannikow ('88), 295 studying the con- 

 ditions in a 65 mm. embryo; Cattie ('82), 6 in the adult, and 

 Galeotti ('96), 14 studying the histology. The proximal portion 

 in these forms is not well developed and the end- vesicle is coni- 

 cal. The middle piece or stalk is cylindrical in shape. The 

 structure, according to Galeotti, shows stellate cells and epen- 

 dymal cells, in addition to which, there are certain cells which 

 are definitely fuchsinophile, which, according to this observer, 

 indicate secretory function because he considers these granules 

 secretory in their nature. 



2. Acanthias vulgaris. Ehlers 108 in 1878 and Cattie 60 in 1882. 

 In this form the proximal portion is thicker than the stalk and 

 both are of unusual thickness for selachians. The end-vesicle, 

 according to Cattie, is solid. Its walls show much reduplication 

 and the lumen is solidly filled with a syncytium. There is a 

 definite parietal foramen. 



3. Echinorhynus spinosus. Jackson and Clarke (75) 193 . The 

 pineal organ in this form is a long, strand-like body extending far 

 over the telencephalon in the midsagittal plane. 



4. Galeus canis. Cattie ('82). 60 A conical end- vesicle and a 

 conical proximal portion with a strand-like stalk characterize the 

 pineal organ in this form. The end- vesicle and the stalk are 

 solid while the proximal portion retains its lumen and has, in 

 addition, many small accessory canuliculae. 



