54 CHARLES BROOKOVER 



for in the remaining living lung-fish, Lepidosiren. Burckhardt, 

 as cited by Pinkus ('05), found the nerve in Callorhynchus. 

 Burckhardt has suggested that its ganglion might be homologous 

 with the ganglion found by Rubaschkin ('02) in the chick, but 

 Rubaschkin considered the ganglion in the chick to be developed 

 as a part of the trigeminus nerve, in all probability. 



Ernst DeVries ('05) described a ganglion in the course of the 

 nerve fibers to the organan vomeronasals (Jacobson's organ) of 

 human embryos of about three and a half to four months. In the 

 guinea pig he found a similar embryonic ganglion. He expressed 

 the opinion that the same relations probably exist throughout 

 the whole series of vertebrates. Although the organon vomero- 

 nasale does not exist as such among a large number of anamniotes, 

 he thinks the nerve described by Locy is probably homologous 

 with the nerve to Jacobson's organ. 



If the nervus terminalis of lower vertebrates is homologous 

 with the nerve to Jacobson's organ or with some part of the nerve 

 to this organ, we may well look for some evidence of a similar 

 nerve or ganglion everywhere in the vertebrate series, for Jacob- 

 son's organ has been described as occuring embryologically or 

 in the adult in forms from Amphibia to man. The literature 

 shows that the nervus terminalis is almost universal among the 

 living generalized fishes. We may have overlooked its presence 

 in the remainder of the fishes. That such may be the case is 

 indicated by the fact that the writer ('08) has found the ganglion 

 among the fibers of the olfactory nerve of the young of two 

 species of Lepidosteus in the identical relations described by 

 Allis for Amia. No mention of such a ganglion has been found 

 in the literature. Also, while this work was in progress the writer 

 found ganglion cells indicating a nervus terminalis in the olfac- 

 tory nerve of the carp, and Sheldon ('09) found its central con- 

 nection with the brain. Sheldon and Brookover ('09) reported 

 its presence in the carp at the Baltimore meeting of the American 

 Association of Anatomists. Meanwhile, Herrick ('09) found 

 the nervus terminalis in the tadpole and in the adult frog. 



Pinkus ('05) in his third paper dealing with the nerve as found 

 in fishes, summarizes its relations with the olfactory nerve by say- 



