564 LOCY. [Vol. XI. 



The above observations, taken together, give sufficient posi- 

 tive data to establish the fact that there appears, from time 

 to time, in some animals the vestiges of accessory pineal 

 organs, and that they are variable and inconstant in their 

 occurrence. 



The most recent advances consist in carrying the history of 

 these organs backwards, and showing them to be connected 

 with patches of sensory epithelium that arise on the cephalic 

 plate in very young stages, and in the discovery, in Iguana, of 

 three distinct nerves connected with the epiphysial outgrowths. 

 The former work was done by the present writer, and the latter 

 by Klinckowstrom. 



As indicated in the preceding section, there are several pairs 

 of cups on the cephalic plate back of the optic vesicle, formed 

 while the neural groove is widely open. I have designated 

 them accessory optic vesicles. In the process of closure of 

 the neural groove the anterior pair are brought together, and 

 form part of the thalamencephalon, from the roof of which the 

 pineal outgrowth is derived. This process will be described 

 more in detail. 



Klinckowstrom ('93) has recently shown in Iguana the pres- 

 ence of two nerves connected with the anterior outgrowth or 

 pineal eye, and sometimes a third connected with the posterior 

 outgrowth or epiphysis. 



These observations suggest new interpretations; still it is 

 not an auspicious moment to indulge in speculation. It is 

 clearly evident that we need more data regarding these organs 

 and their relationships. But the trend of these discoveries is 

 to strengthen the suggestion already made in this paper, that, 

 primitively, the Vertebrates were multiple-eyed. The presence 

 of accessory pineal eyes, the discovery of serial sensory areas 

 on the cephalic plate from which epiphysial outgrowths arise, 

 and the presence of two or three pineal nerves, are all consist- 

 ent with this interpretation. So far as the evidence goes, 

 there is more than one epiphysial outgrowth, and therefore I 

 have headed this section, The Pineal Sense-Organs. In what 

 way it will be necessary to qualify this proposition will depend 

 on subsequent discoveries. 



