"2. Various species of bird Taenia live always in one of the 

 26 groups of birds now distinguished by us. During the verification of the 

 correctness of all the data of the authors, it appears that the majority of 

 the species is even more specialized in regard to the place of habitat. " 



In the work of 1932 on tapeworms of birds Fuhrmann again p. 294 



confirms his conclusions, formulating them somewhat differently: "In 

 spite of a more fractional subdivision of all the birds (in comparison with 

 the 26 orders of birds accepted in 1909, 45 are accepted in the work of 

 1932) (Fuhrmann's generalization of 1909, nobis ) it remains true that 

 each order of birds possesses its special fauna of cestodes. Among 

 hundreds of Taenia of the birds of the entire world which we are determining 

 there has not been a single case contradicting this rule. " Just as in the pre- 

 ceding work, Fuhrmann analyzes the literary indications which do not fit 

 this rule and in all cases comes to the conclusion that either there is an 

 error in the determination of the species of the tapeworms or the infor- 

 mation of the author does not deserve sufficient trust. Evaluating questions 

 of occurrence of the cestodes of the birds, Fuhrmann further indicates that 

 he does not exclude the possibility of separate cases of finding worms on 

 orders of hosts which are not peculiar to them, but thinks that this can 

 happen very rarely because the identical chemistry of the intestines of the 

 birds can be encountered in different orders very rarely. However, he 

 considers it indispensable to clarify the questions (in these exceptional 

 cases, nobis) of whether the parasite is developed normally and whether 

 this is not a case when very close but independent species in these birds 

 are encountered. 



_ - — 



Naturally we do not deny absolutely that a species of Taenia of a 

 particular bird order cannot accidentally and as an exception be located in 

 a bird belonging to another order; but if similar cases occur it would be 

 interesting to know whether the parasite in this exceptional habitat shows 

 normal development or not, or whether it is rather a case of a very close 

 species, as happens for instance in Hymenolepis fraterna of the rat and 

 Hymenolepis nana of man which cannot be distinguished from each other 

 but which nevertheless represent two different species (Fuhrmann, 1932, 

 pages 18-19). 



These statements are very interesting because they help us to 

 understand correctly the point of view of Fuhrmann about the normalities 

 (principles, nobis) established by him. Not less important are his con- 

 siderations about the fact that the data on tapeworms do not provide any 

 basis so far, because of their insufficiency, on which to maintain that 

 consanguinous relations of the host play a greater role in the distribution 

 of the parasites than the geographical or ecological factors, although he 

 considers this quite possible. All in all "the rule of Fuhrmann, " if one 



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