374 University of California Publications in Zoology. [VOL. 6 



[of Gyrocotyle rugosa] obtained by myself three in number 

 were taken from the mouth of Callorhynchus antarcticus, and 

 their presence in such a position was doubtless associated with 

 the fact that the fish had been dead some twenty-four hours, 

 though the parasites were still living and evidently trying to find 

 their way out of the dead body." Wagener (1852, p. 543) says: 

 "Nur einmal fand es sich an den Kiemen, wobei jedoch bemerkt 

 werden muss, dass die Fisch schon 12 Stunden ausserhalb des 

 Wassers sich befand." Lonnberg (1891) mentions the finding of 

 G. urna living free, but supposes the worms to have finished 

 their cycle and to have been cast out with the excrement of the 

 host. He seems to imply in the following statement that the 

 worms leave the dead host (writing of the almost invariable 

 occurrence of the parasite in Chimaera) : ''In zwei anderen, die 

 ich in Upsala untersuchte, die aber von Trondhjem stammten, 

 habe ich ihn nicht gefunden, aber diese Fische waren schon seit 

 mehreren Tagen ausserhalb des Wassers." It may then be re- 

 garded as an established fact that the parasite is capable of a 

 very considerable amount of locomotion, and that it can, under 

 favorable conditions, leave its. host and live for some days outside 

 the intestinal tract. The most important condition seems to be 

 temperature; a low temperature (about 10-12 C.) is most 

 favorable. In warm weather the worms remain active for only 

 a very short time, and have never succeeded in getting out of 

 the intestine in any case under my observation. This ability 

 to leave the host, taken in connection with the behavior of the 

 isolated parasite as described below, has an important bearing 

 both on the problem of orientation and on the question of the 

 habitat of the parasite, which will be discussed later. 



The worms on being removed from the fish were placed in 

 culture fluids. The worm is very active, if removed soon after 

 the death of the fish and kept at a low temperature. The culture 

 solution quickly becomes contaminated with bacteria, and the 

 worm contracts and grows sluggish. When changed to fresh 

 solution the parasite expands and renews its movements. These 

 consist of the following : 



1. Thrusting and exploring movements of the acetabular ex- 

 tremity, accompanied by contraction and expansion of the body. 



