299] PROTEOCEPHALIDAE—LA RUE 299 



take batrachians and crustaceans in addition to the fish. This species 

 is no doubt carnivorous in habits. The writer is unable to find anything 

 about the food of Clarotes laticeps. It seems probable, however, that 

 it is a carnivorous species as are many others of the Siluridae. That 

 this parasite is able to find the proper conditions of life in two species 

 as widely separated as are these seems remarkable altho not more 

 remarkable than that Amia calva may serve as the host of a species 

 characteristic of the Centrarchidae. It has, however, been pointed out 

 in the descriptive part of the work on this species that there seems to 

 be some reason for believing that two species have been confused under 

 the one name. 



Proteocephalus torulosus 



This species is known only from northern and central Europe, 

 chiefly from the Baltic drainage. Its hosts are chiefly cyprinids. All U^ 

 the earlier reports record it only from cyprinids. During the last few 

 years it has been reported from Salmonids, four species, and from Perca '"" 

 fluviatilis and Lota vulgaris. A table is appended showing the names 

 of the hosts as reported, their distribution, and their food. As to food 

 the data are very fragmentary and not specific yet they are of interest. 

 An examination of the table shows that the hosts are common in the 

 waters of the lakes and streams of central and northern Europe. Some 

 hosts are of wide distribution, others more or less restricted. Many of 

 these hosts occupy the same waters, some as surface dwellers, others as 

 bottom dwellers, some in the deep lakes, others in the small streams, while 

 still others occur in the brackish bays and inlets of the Baltic coast. 

 Thus the habitats are quite varied. 



The food taken by the host varies to a large degree with the habitat 

 which the host prefers. Thus from the table it is found that the food 

 habits of the hosts listed are very different. Some are exclusively 

 plankton feeders, others feed largely on bottom fauna or bottom fauna 

 with plankton. Still other hosts are largely eaters of fish. If the food 

 of the two groups of hosts, cyprinids and non-cyprinids, be considered 

 it is noted that each of the latter group takes several kinds of food. 

 This statement applies only to those non-cyprinids the food of which 

 is known. Each of the cyprinids, however, takes but few kinds of food. 

 The table speaks for itself. The cyprinids of the table are chiefly feed- 

 ers on bottom fauna. Plankton forms a large part of the food of three, 

 and fish of two of these hosts. Certain elements in the food such as air- 

 borne insects, birds, plants and probably also amphibians (semi-terres- 

 trial forms especially) do not function as intermediate hosts for Pro- 

 teocephalus species. For this reason they need not enter into this 

 discussion. 



