360 KANSAS UNIVERSITY SCIENCE BULLETIN. 



the heart of the Corethra laiwa. In only a few cases did he 

 find processes on the cells. He also found ganglion-cells in the 

 auricle of the snail's heart. 



Ransom/ however, thinks Dogiel is mistaken in calling these 

 cells ganglion-cells. Instead he thinks they are "wandering 

 connective tissue" cells, probably the same as the "plasma- 

 cells" described by Brock."^ He found cells similar to Dogiel's 

 ganglion-cells in the auricle of Aplysia and in Pterotrachea in 

 the connective tissue all over the body. In Helix he found the 

 "plasma-cells" in various stages of division, but in no case 

 did he find tvhat he could call true ganglion-cells, or nerve-cells, 

 in the substance of the rhythmically contractile organ, but he 

 did find nerve-fibers. Octopus and a tunicate were also exam- 

 ined by him, but with the same results. 



In Aplysia, Ransom described these cells as being roughly 

 spherical with deeply staining nucleus and a clear, slightly 

 staining cell substance. In Pterotrachea the cells are round- 

 ish, possess a not very distinct oval nucleus placed near the 

 periphery of the cell, and often a nucleolus. There is no definite 

 capsule. In Helix these cells were found in various stages of 

 division. They somewhat resemble cells that I found in the 

 grasshopper, which will be described later. 



Ransom also states that other cells which might be taken 

 for nerve-cells are nothing more than ordinary connective-tis- 

 sue cells. He says: "In no molluscan or tunicate heart ex- 

 amined are ganglion-cells to be found." Foster*^ thinks they 

 do not exist, and Darwin,'^ Ransom and Biederman all say that 

 the snail's heart has no ganglion-cells, although Ransom says 

 nerve-fibers do enter the heart. Dogiel believes them to exist 

 in the auricle. 



Among the works of more recent investigators concerning 

 the activity of the heart-muscle of the invertebrates, Carl- 

 son's^ is perhaps the most extensive. Aside from his observa- 

 tion, the majority substantiate the myogenic theory of con- 

 traction. Carlson's work on invertebrates has included a few 

 experiments on insects, and a microscopic examination of the 

 heart of tarantula, polyphemus moth, and the grasshopper, 



4. Ransom, Jour, of Phys., vol. 5, p. 324, 1884. 



5. Brock, Zeit. f. Wiss. Zool., Bd. 39, 1883. 



6. Foster, Pfliiger's Archlv., vol. V, p. 191. 



7. Darwin. .Jour, of Anat. a. Phys., vol. X, part III, 1876. 



8. Carlson, A, .T., Amer. Jour, of Phys., vol. XV, 1906, No. II, p. 130. 



