No. 3-] THE VERTEBRATE HEAD. 563 



respectively, in the Cyclostomes. As I shall show later, the 

 so-called paraphysis is a different structure. 



Beraneck showed that the pineal eye and epiphysis have 

 been confused, and, on account of the existence of the nerve 

 from outside sources, he argued for the complete independence 

 of the pineal eye. 



Klinckowstrom has placed himself in opposition to this 

 opinion, showing the eye vesicle is formed as an outgrowth 

 from the epiphysis. 



Next to the discovery of two or more epiphysial outgrowths 

 may be mentioned the existence of accessory pineal eyes. The 

 earliest publication containing an account of such structures is 

 that of Duval and Kalt, in 1889. In a brief note (Des Yeux 

 Pineaux Multiples chez I'Orvet) these authors record the 

 finding of two or three accessory pineal vesicles in Anguis. 

 They do not say whether adult or embryonic forms were 

 studied. 



Carriere ('89), in the same year, noted the occurrence in em- 

 bryos of Anguis of a very rudimentary accessory pineal vesicle. 



Leydig ('9o) observed these structures independently in 

 embryos of the same animals. He showed that there is much 

 variability, both as to the presence and the histological struc- 

 ture of these accessory capsules. In some individuals they 

 are lacking, and in others of the same age present and well 

 developed. He records the occurrence, in some cases, of two 

 accessory organs, a larger and a smaller one. The larger one 

 resembles the pineal eye in structure and arrangement of pig- 

 ment. The smaller one is very rudimentary. Leydig com- 

 pared them to the ocelli of insects. It is clear from his account 

 that variability and inconstancy are characteristics of these 

 accessory organs. 



Prenant, in the latter part of 1893, again records the occur- 

 rence of one accessory pineal eye in the embryos of Anguis. 

 He directs attention to the fact that up to that time they had 

 been discovered only in a single species, viz., Anguis fragilis, 

 and further, that they were all in embryos, and not in adults. 

 Ritter ('94) has recently recorded the occurrence of such an 

 accessory organ in the adult Phrynosoma. 



