HerrICK, Conimissiira Infiuia. 417 



infima contains at the cephalic end a large, heavily medullated 

 tract from the funicular nucleus, and farther back extensive more 

 diffuse connections between the first and second accessory lobes. 

 The somatic commissural nucleus is also very large and associated 

 with the tracts last mentioned. The commissural nucleus does 

 not extend back beyond the cephalic end of the second accessory 

 lobe, though there is a well developed medullated dorsal commissure 

 between all of the accessory lobes. 



The commissura infi7na of Amia calva. — In this fish both the 

 visceral and the somatic commissural systems are moderately 

 developed and the whole region is simpler and probably more primi- 

 tive than in any teleost examined. 



The vagal lobes are elongated and their caudal ends rise up to 

 form the lips of the fourth ventricle (taenia ventriculi quarti) in the 

 calamus region, fusing together behind the ventricle to form the 

 visceral commissural nucleus (fig. 11). Sparse unmedullated 

 fibers cross the medial plane within this nucleus, constituting the 

 visceral commissura infima. This nucleus contains but few cells 

 and is broadly connected with the homolateral formatio reticularis 

 ventrally of the funicular nucleus. 



The funicular nuclei are elongated, extending from the level 

 of the visceral commissural nucleus caudad far into the spinal 

 cord. The somatic commissural nucleus (fig. 12) contains many 

 densely crowded cells extending from the ventro-mesial borders 

 of the two median funicular nuclei and across the meson ventrally 

 of the most caudal part of the visceral nucleus and close above the 

 canalis spinalis. There are no medullated fibers in the somatic 

 commissural nucleus and very few unmedullated fibers. 



Kappers (1907, p. 490) has briefly referred to the commissura 

 infima of Amia, but he was not able to demonstrate definite com- 

 missural nuclei. He says, referring to the visceral commissural 

 nucleus, " Ich mochte ihn lieber nicht als besonderen Kern betrach- 

 ten." It is true that the visceral nucleus is not so large and clearly 

 defined in Amia as in the teleosts which I have examined, yet its 

 individuality is perfectly clear, as I have seen in an extensive series 

 of sections of Amia kindly loaned to me by Prof. Charles Brook- 

 over. These include preparations by the methods of Weigert, 

 NissL, Cajal, Bielchowsky and the iron haematoxylin method of 

 Haidenhain. I have chosen for illustration (figs. 11 and 12) a 

 teries through a young specimen stained by the method last men- 

 sioned. The adult relations are similar. 



