Johnston, Giant Ganglion Cells. 379 



bipolar cells in the dorso-median part of the cord which send 

 their nervous processes into the sensory roots. These cells cor- 

 respond (Kolliker) to the above mentioned cells in Amphioxus, 

 and Petromyzon presents an intermediate condition between 

 Amphioxus and the higher vertebrates. The presence of these 

 cells in Petromyzon also lends support to Kolliker's hypothesis 

 regarding the neural crest. 



In Pristiurus embryos, according to Lenhossek's researches 

 ('92), some fibers pass through the spinal ganglia without con- 

 nection with ganglion cells. It is possible that these arise from 

 cells within the cord, corresponding to those in Petromyzon. 



Tagliani ('98) states that in Solea impar and Orthagoriscus 

 mola the greater part of the giant cells send their fibers caudad 

 in a bundle from which occasional fibers go toward the sensory 

 roots among the fibers of which they are lost. He thinks that 

 in these two forms, as also probably in Lophius piscatorius, a 

 part but not all of the fibers of the giant cells enter the dorsal 

 roots. A few fibers from the giant cells run rostrad in a bundle 

 which is lost on the floor of the medulla lateral to the fasciculus 

 longitudinalis posterior. He concludes: " dass die Nerven- 

 fortsatze der Riesennervenzellen sich nicht im Fasergewirr der 

 spinalen und bulbaren Centren auflosen, sondern als nackte 

 Nervenfasern zu centrifugalen (motorischen) Elementen der 

 dorsalen, spinalen, oder bulbaren Wurzeln werden." 



From these investigations it appears that in Amphioxus, 

 Cyclostomes, Selachians (?), and Teleosts cells are present in 

 the spinal cord which give rise to fibers of the dorsal roots of 

 the spinal nerves. In Amphioxus and Petromyzon these fibers 

 are certainly afferent (sensory) and it is to be presumed that 

 the same is true in Selachians and Teleosts. The disposition 

 of the processes of these cells within the cord is known only 

 in Amphioxus, where they correspond in a general way to 

 the central processes of the spinal ganglion cells in higher ver- 

 tebrates. The cells described in the present paper have periph- 

 eral processes distributed to the integument and central pro- 

 cesses (neurites) running in the dorsal tracts and ending in the 

 dorsal horns and the nucleus funicuH. This justifies the con- 



