340 L. H. HYMAN AND A. \V. BELLAMY. 



the most oxygen, anterior pieces next, and middle pieces least 

 (Hyman and Galigher, '21). 



2. The Electrical Gradient. It was found by Morgan and 

 Dimon ('04) that in two species of earthworm, Lumbricus tcr- 

 rcstris and Hclodrilus (Allolobophora} fcetida, the anterior and 

 posterior ends are, in general, electronegative (galv.) to the middle. 

 This result was verified by Bellamy on Helodrilus caliginosus. 

 Other oligochsetes have not as yet been tested. 



Among the polychsetes experiments have been performed chiefly 

 on Nereis, Nereis virens on the Atlantic coast by Hyman in 1919 

 and Nereis virens and Nereis vcxillosa at Friday Harbor by 

 Bellamy in 1918 and Hyman in 1920. It was found that the elec- 

 trical conditions are highly dependent on the freshness of the 

 animals. It appears that in both species the two ends are negative 

 (galv.) to the middle in very freshly collected animals, but the data 

 are not as yet conclusive. It is certain, however, that when the 

 animals have been kept in the laboratory, if only for a few hours, 

 the gradient is reversed, and the anterior end is always and the 

 posterior end usually positive (galv.) to the middle. Table VI. 

 gives data on the electrical conditions in laboratory animals of 

 both species. 



3. Galz'anota.i'is. The galvanotactic response of oligochsetes and 

 leeches was tested by Blasius and Schweizer ('93) for the leech, 

 Branchiobdella, and Lumbricus, and by Nagel ('95) for the leech, 

 Lumbricus, and Tubifcx. These authors found that all of these 

 forms are definitely cathodic, turning their anterior ends toward 

 the cathode, and usually crawling toward the cathode. The matter 

 was investigated in more detail by Moore and Kellogg ('18) for 

 Lumbricus tcrrcstris. They noted that this species bends into a 

 U-shape when placed in the current with anterior and posterior 

 ends directed toward the cathode, middle toward the anode, and 

 crawls toward the cathode maintaining this posture. Bellamy 

 found the same behavior in Hclodrilus caliginosus. Hyman has 

 tested the behavior in the current of Dero limosa and Lumbriculus 

 inconstans. Both are markedly cathodic. The former instanta- 

 neously places itself with longitudinal axis parallel to the current, 

 head to the cathode, and crawls rapidly to the cathode. Lumbricu- 

 assumes the same posture as Dero, except that the posterior 



