THE PINEAL BODY 205 



epiphysis is wanting, since these are considered, by most author- 

 ities, as degenerated forms. 



With these exceptions, then, so much in the minority, this 

 negative evidence should be accepted with much hesitancy. 

 In fact, the phyletic constancy of the epiphyseal complex is so 

 pronounced as to render the total absence of the organ in Myxi- 

 noids, Torpedo, and Crocodilia open to doubt. 



b. Phyletic variations and morphologic specialization. If the 

 constancy already considered lends itself to the weight of evi- 

 dence in favor of the supposition that the pineal body is a func- 

 tional organ, then even more will the phyletic variations and 

 morphologic specializations which present themselves in this 

 organ support the view that the epiphysis is not a vestige, but 

 plays some physiologically definite role. 



Certainly, when the marked specialization in the epiphyseal 

 complex in the various orders of vertebrates is taken into ac- 

 count, it is difficult to escape the conclusion that such modifica- 

 tions must have been in the interest of definite adaptations. 

 If these specializations referred to were indefinite or diffuse, it 

 might still be a question whether the processes were actually in 

 the interest of adaptation; but when, as is the case, form after 

 form shows such a high state of differentiation, such a definite and 

 discrete specialization, there seems to be little room for doubt 

 that a process of adaptation has been carried forward in order 

 to satisfy the demands for the development of specialized organs. 



On the other hand, it cannot be denied that even such discrete 

 differentiation as the epiphyseal complex presents in many 

 forms, may represent but the rudiments of an adaptive process 

 which in some extinct forms, or perhaps even in some of the 

 proto- vertebrates, may have attained their functional consum- 

 mation only to impart an impulse in this direction to those verte- 

 brates which show the most definite specialization in the pineal 

 organs. 



In this sense, all of the differentiation of the epiphyseal com- 

 plex throughout the vertebral phylum expresses an inherent 

 attempt to consummate the formation of organs which have 

 been essential in extinct forms or in the ancestors of the verte- 



