The morphology and evolutional significance of the pineal body : being part I of a contribution to the study of the epiphysis cerebri with an interpretation of the morphological, physiological and clinical evidence . terior; Cp., commissura posterior; M, midbrain. epiphysis in amphibia arises as two primary outgrowths fromthe roof of the forebrain (fig. 21). These are placed one on either side of the mesial plane. Theoutgrowth situated to the right of the middle line disappears atan early age by blending with the left outgrowth. The lattershows most active growth so that the epiphyseal opening
The morphology and evolutional significance of the pineal body : being part I of a contribution to the study of the epiphysis cerebri with an interpretation of the morphological, physiological and clinical evidence . terior; Cp., commissura posterior; M, midbrain. epiphysis in amphibia arises as two primary outgrowths fromthe roof of the forebrain (fig. 21). These are placed one on either side of the mesial plane. Theoutgrowth situated to the right of the middle line disappears atan early age by blending with the left outgrowth. The lattershows most active growth so that the epiphyseal opening becomessituated to the left of the mesial plane. The left outgrowth, 56 FREDERICK TILNKV AXI) LUTHER F. WARREN however, is the more important of the two in amphibia. Cam-eron believes that there is evidence of a bilateral origin to befound in the later stages of amphibian development. Theportion of the anlage in connection with the superior commissurecorresponds to the parietal eye of Sphenodon while the remaindercorresponds to the epiphyseal stalk. From this evidence inamphibia he is inclined to agree with Dendy86 that the ancestorsof vertebrates must have possessed a pair of parietal eyes ( and 23).. Fig. 21 Anlagc of the epiphyseal complex in an embryo of Triton cristatus,according to dodraaf, 1886. (It , commissura habonularis; If., recossus and pineal organ; Cp., commissuraposterior; M., midbrain; Epid., epidermis; Cor., corium. 6. The development of the epiphyseal complex in reptilia The fact that in Prosanrnmx and Saurians a well deveopedeye is found in many fcrms has been the cause of much dis-cussion ;is 1o the embryolgical process by means of which thisstructure is differentiated from the epiphyseal complex. Accord-ing to the older view, the p;trital eye arose, as in the case of theisolated end-vesicle of amphibia, by a process of constrictionfrom the terminal portion of the pineal organ. Subsequentlythe view was advanced that instead of a process of constrict
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