114 FREDERICK TILNEY AND LUTHER F. WARREN 



5. Comparative anatomy and histology of the epiphyseal complex 



in amphibia 



In amphibia the pineal organ alone makes its appearance. 

 In no other form is this organ so little developed. It presents a 

 small end-vesicle which Stieda 379 first recognized and described 

 as the frontal subcutaneous gland. This end r vesicle is attached 

 by means of a thread-like strand to a considerably expanded 

 proximal portion, to which latter the name of epiphysis or corpus 

 pineale has been ascribed. The pineal organ consists, there- 



Fig. 60 Head of Rana temporaria showing the unpaired pineal eye, situated 

 between the paired eyes, according to Stieda, 1865. 



fore, of the usual parts, namely, an end-vesicle, a stalk, and a 

 proximal portion which is particularly conspicuous in amphibia. 

 The end-vesicle' in so far as is known, is present in all forms 

 except Hyla arborea, the absence in this form being noted both 

 by deGraaf, 155 and Leydig. 238 In shape, the end-vesicle is round, 

 oval, or kidney-shaped. Stieda 379 and deGraaf 155 found it solid, 

 containing a lumen only in Bombinator. According to Stieda, 

 its diameters are from .12 to .15 mm. deGraaf found these 

 diameters in Rana esculenla from .126 to .145 mm., while 

 Lessona 241 in the forms studied by him found that the diameter 

 was less than 1 mm. A number of observers, including Ostrou- 

 moff 29 i ('87); Leydig 233 ('91); Galeotti 140 ('96), and Braem 39 ('98), 



