THE PINEAL BODY 



67 



7. The development of the epiphyseal complex in aves 



In birds, the anlage of the epiphyseal complex makes its first 

 appearance as a simple and single evagination. This was first 

 observed and described by Reissner 329 in 1851 and called by 

 Reichert 326 in 1859 the recessus pinealis. Lieberkiihn 242 in 1871 

 identified this evagination in birds as the anlage of the epiphysis. 



In many instances the presence of a double evagination of 

 the roof-plate has been reported in the anlage of the epiphysis 

 in birds. Saint Remy 340 in 1897 found on either side of the still 

 unclosed neural tube a small evagination in the region of the 



Fig. 34 The epiphyseal complex in an 8-day embryo of Anas domesticata, 

 according to Hechscher, 1890. 



epiphyseal anlage. This observation was made upon Callus, 

 but Parker 301 in 1892, in Apieryx, and Klinckowstroem 20 ' in 

 1892, in Larus, mentioned an evagination in front of the epi- 

 physeal anlage. Hill 181 in 1900 observed in a closed neural tube 

 two such evaginations. Whether it is justified to consider the 

 anlage of the epiphysis in birds as bilateral or double or whether 

 one of these evaginations represent the remnant of the para- 

 pineal organ, is a difficult question to decide. By many these 

 reduplications in the anlage are considered as pathological since 

 they occur only in isolated instances of the several species 

 described. The most common form in which the anlage in birds 



