767 



this term I particularly emphasize my belief in a strict homology 

 between the two organs. 



The structure is shown in the accompanying figure, vs'. It is 

 situated anteriorly and somewhat though not greatly to the right of 

 the pineal eye, vs., and has about the same relation as the latter to 

 the epidermis. Both vesicles are embedded in the connective tissue 

 which fills the pineal foramen of the cranial roof. Pigment is absent 

 from the tissue over the parapineal organ as well as from that over 

 the eye. As shown by the figure, the distinct and thick layer of 

 connective tissue that encapsules the retinal portion of the eye also 

 extends for a distance along the under side of the secondary vesicle. 



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Sagittal section of the dorsal cranial wall of an adult Phrynosoma coronata. 

 v.s. pineal eye; v.s'. parapineal vesicle; p.b. parietal bone; pig. pigment; wh. pig. white 

 pigment ; I. lens ; rt. retina ; ep. epithelium of integument. 



Outlines drawn by aid of camera lucida. 



(It does not, however, reach as far around the latter as it does 

 around the former.) This tissue contains white pigment. There is 

 no organic connection between the two vesicles, and neither is 

 connected with the epiphysis; much less, then, of course, with the 

 brain. 



The parapineal organ is somewhat larger than the pineal eye, 

 and as to general form resembles it considerably, each being a strongly 

 oblate spheroid. The secondary vesicle is not quite as regular in form 

 as is the eye. It is 228 mm in its greater diameter, and 171 mm in 

 its lesser. 



In its details of structure it differs notably from the eye. There 



