214 CONSIDERATIONS OF CLASSIFICATION AND METHODS 



In case of larva and adult or male and female, formerly considered different 

 animals but subsequently found to be the same, the oldest available name becomes 

 the name of the species. 



Another point is that names are not definitions, consequently the fact of lack 

 of appropriateness of any name is no objection to its continuation. This will ap- 

 peal to anyone as a wise provision, because if a different name were substituted 

 each time a designation more descriptive or applicable was invented it would be 

 utterly destructive to system. When it is considered that some of our parasites 

 have approximately fifty different designations, for the most part given by med- 

 ical observers, it will be appreciated how much the zoologist has aided us in trying 

 to eliminate all but the single proper zoological name. 



The objections so frequently heard among physicians in connection with adopt- 

 ing new names for old ones are not well founded. Wherever confusion has reigned, 

 the establishment of order always results in temporary greater confusion. There 

 is no doubt that the student taking up this subject a few years hence will have the 

 satisfaction, thanks to the zoologist, of only having to burden his mind with one 

 name for one parasite. 



There is only one correct name for an animal and all other names 

 are synonyms. 



The principal cause of changes of names is that our conception of the relation- 

 ships of animals changes. 



5. Terminology. This applies to appropriate designations for different organs, 

 symptoms, etc., and is not subject to any rule other than that of good usage. 



Thus the terms cirrus in the case of the male copulatory organ of flukes, spicule 

 for the same in nematodes and penis in connection with insects would be instances 

 of terminology. 



6. Pseudoparasitism. Where organisms enter the body accidentally and when 

 such sojourn in the body of man plays no part in the life history of the organism 

 we employ the term pseudoparasitism. For example: Fly larvae swallowed by 

 man and passed out in the faeces. We also use the terms temporary parasites 

 (bedbug) and permanent parasites (liver fluke). 



7. Hosts. The animal in which a parasite undergoes its sexual life is called the 

 definitive or final host, that in which it passes its larval existence the intermediary 

 host. For example: Man is the intermediary host of the malarial parasite, the 

 mosquito the definitive host. A single animal may, however, be both definitive 

 and intermediary host; thus Trichinella may pass its larval existence in the muscles 

 of man and its sexual life in his intestines. 



8. Heredity, Congenitalism. Hereditary characteristics are those which were 

 present in the ovum or spermatozoon before fertilization; congenital ones those 

 which occur after fertilization. South African tick fever is probably an instance 

 of heredity, the spirochaetes having been found in the ovary and ova of the female 

 tick. 



9. Heterogenesis, Parthenogenesis. Offspring differs from parent, but after 

 one or more generations there is reversion to the parent form. 



Strictly speaking the term heterogony applies to reproduction when a sexual 



