54 FREDERICK TILNEY AND LUTHER F. WARREN 



the anlage of the epiphyseal complex to be a hollow sac which 

 later became saccular and cylindrical, containing throughout its 

 entire extent a lumen which still opened into the third ventricle. 

 In this form it was possible to identify an end- vesicle, a stalk, and 

 a proximal portion. These conditions were obtained at a period 

 of 12 mm. embryo, but at the stage of the 18-mm. embryo the 

 lumen in the stalk was obliterated. In this manner the stalk of 

 the pineal organ became gradually reduced in size until finally 

 it presented itself as a mere strand connecting an almost com- 

 pletely isolated end-vesicle lying beneath the skull with a well- 

 marked proximal portion in communication with the third 

 ventricle. In Salamandra the paraphysis develops very early 

 and assumes extensive proportions resembling the chorioid 

 plexus. The embryological conditions in Anura are, according 

 to most descriptions, quite similar to those in Urodela. Goette 152 

 in 1873-75 observed in the anlage of the pineal organ the remains 

 of the anterior neuropore. This error, as has already been 

 stated, was pointed out by Hoffmann 186 in 1886 and Heckscher 1690 

 in 1890. In Rana, Beraneck 24 described the first appearance of 

 the anlage of the epiphyseal complex as a small, ellipsoid evagi- 

 nation which later becomes cylindrical. This evagination con- 

 tains a small lumen. Elongation gradually occurs so that an 

 end-vesicle, a stalk, and a proximal portion are formed. In the 

 later stages of development the stalk undergoes attenuation 

 until it is reduced to a mere strand containing, it is thought, 

 some nerve fibers. This leaves the end- vesicle situated at a 

 point remote from the brain beneath the skull, while the proximal 

 portion is a large and somewhat spacious evagination still main- 

 taining a wide connection with the third ventricle. The nearly 

 isolated end-vesicle Beraneck calls the corpus epitheliale. This 

 body lies beneath the skin over the head and has the appearance 

 of a gland-like structure. In embryos of Bufo, Beraneck 24 

 observed close to the commissura habenularis a small prominence 

 which early disappears; this he identified as the anlage of a 

 transitory parapineal organ. For the most part, however, 

 observers have found that a single evagination in the roof-plate 

 marks the anlage of the epiphyseal complex (fig. 20). 



