KUTCHIN. — PERIPHERAL NERVOUS SYSTEM OF AMPHIOXUS. 597 



here as in other regions. In transverse sections stained with Mal- 

 lory's differential stain, portions of the larger plexus may be seen lying 

 on the inner surface of the transverse muscles, in connective tissue. 

 Since many of the threads of the finer plexus are nearer the surface of 

 the atrial cavity than those of the coarser plexus, they must be closely 

 associated with the bases of the cells lining that cavity. In portions 

 of my preparations the finer plexus is extremely complicated, and the 

 meshes are not decidedly elongated. The meshes of the main inner 

 abdominal plexus sometimes appear knotted in methylene-blue prepara- 

 tions, even though the knots are not differentiated in any way; but ap- 

 parent nuclei are frequently present in the course of the nerve threads 

 and at places of junction. Certain large meshes of the inner abdominal 

 plexus send branches to the gonadial pouches (PI. 3, Fig. 13, i.), 

 although the main supply for these structures is derived from the ramus 

 visceralis ascendens. In Golgi preparations of Branchiostoma cari- 

 baeum, nerve threads were found scattered in the transverse muscles. 

 It was impossible to determine their origin, but closely associated 

 threads evidently did not all lie in the same focus. The greater 

 number of these tlireads are arranged more or less nearly parallel 

 to the long axis of the animal (PI. 5, Fig. 23). 



Impregnation with methylene blue does not always produce the 

 same results in the structural appearance of these visceral nerves. 

 In some preparations the threads of the inner abdominal plexus 

 appear granular, while in others distinct fibers can be traced. But 

 notwithstanding these variations, the visceral nerves can always be 

 distinguished from the cutaneous nerves by their rougher outlines. 



Rami viscerates ascendentcs. — Johannes Miiller ('41, '44, p. 96), 

 and Leuckart und Pagenstecher ('58) observed nerves passing to the 

 branchial basket. Schneider (*79, p. 15) observed and figured sen- 

 sory nerve branches penetrating to the interior at the ventral border 

 of the side muscles. These branches ramify as they ascend on the 

 surface of the abdominal cavity. He ascribes the function of the 

 vagus to these nerves. Rohon ('82, p. 24) agrees with this interpreta- 

 tion. He also describes in some detail, the distribution of nerves in 

 the ligamentum denticulatum, and in the branchiae, Fusari (*89, 

 p. 130) describes the branchial nerve branch as ascending obliquely 

 upward and forward after penetrating to the interior, finally joining the 

 branchial apparatus by way of the ligamentum denticulatum. He 

 states that only the more anterior nerves send branches to the branchiae 

 and that the nerves of the tail also lack the "sympathetic" branch. 

 It will be remembered that Fusari designates the ner\'es of the inner 



