EN
In this article the author compares two final host of Diphyllobothrium latum, dog and man. Basing on the data of Le Basa (1924), Kuhlov (1955) and on her own observations the author states that the dog gets as easily infected as man. The extensiveness and intensity of the infection show but little differences in both of these hosts. However, the considerably longer lifetime of the parasite, its larger body dimensions and shorter sexual mature period in the human organism indicate to the man being the proper final host of Diphyllobothrium latum and the dog acting only as a substitute. The author's investigations do not confirm the opinion of Essex and Magath as to a very low percentage of the hatch of eggs coming from specimens which have a dog as host. In the author's experiments the average hatch of the eggs amounted to 50%. In the conclusion the author indicates to the well known phenomenon of principal hosts and substitutes (in the lower development phases - procercoid, pierocercoid) in the Pseudophyllidaea group and suggests the possibility of similar categories exsisting among the final hosts of D. latum.