THE PINEAL BODY 29 



The work of Galeotti 140 in 1896 on these forms is of particular 

 interest. This observer, applying certain means of cellular 

 differentiation in the technique, showed that some cells of the 

 pineal organ give definite evidence of secretory activity. In 

 Leuciscus he found that the nuclei of the cells contained fuch- 

 sinophile granules and also that the nucleoli in these nuclei 

 were often extruded and later appeared in the protoplasm of the 

 cells. The product of such secretion in Galeotti's opinion was 

 delivered to the cavity of the organ. 



The chief difference between the pineal region in ganoids and 

 teleosts lies in the fact that in the latter forms the paraphysis is 

 entirely absent while in ganoids it constitutes a conspicuous 

 element. 



5. The pineal region in dipnoi 



In dipnoi the only portion of the epiphyseal complex which 

 develops is the pineal organ and this is much less well defined 

 than in the lower forms. No anlage of the parapineal organ 

 makes its appearance. The paraphysis develops later than the 

 pineal organ. The lamina snpraneuroporica, according to 

 Burckhardt ('90), 42 as it appears in Protopterus, is very thick 

 and well developed. The absence of any well-defined velum 

 transversttm makes it appear as if the paraphysis were an an- 

 terior division of the dorsal sac, and yet .a paraphysis may be 

 said to exist in these forms, although no sharp line of demarca- 

 tion may be drawn between it and the dorsal sac. The para- 

 physis itself presents a number of transverse folds beginning in 

 the attenuated membrane immediately dorsal to the lamina 

 supraneuroporica. In Ceralodus the entire paraphysis has the 

 appearance of a glandular structure, the lumen of which is in 

 connection with the ventricle of the brain by means of a small 

 canal. Although an actual velum transversum does not, in the 

 strict sense, exist, Kerr ('03), 202 in Lepidosiren, and Studnicka 

 ('95, '96), 386 in Ceratodus, have both described several folds in a 

 position dorsal to the paraphysis. The dorsal sac is but little 

 developed, although it does appear as a membranous structure 

 extending from the roof of the interbrain. No pars intercalaris 



