474 Dr. O'Bryen Bellingham on Irish Entozoa. 



names which are already too numerous. But in the present in- 

 stance I do not think the new names are an improvement upon 

 the old j the latter appear to me to be more expressive, and their 

 having been adopted by the best practical helminthologists is a 

 sufficient reason for retaining them here. 



Rudolphi has arranged the Entozoa in five orders ©^families, 

 each of which includes a larger or smaller number of genera. On 

 the present occasion I shall only notice those genera in which I 

 have as yet detected species inhabiting animals natives of this 

 country. 



Commencing with those most highly organized, they are Ne- 

 matoidea, Acanthocephala, Trematoda, Cestoidea, and Cystica. 



Order 1. NEMATOIDEA. 



(Derived from vrj}ia, filum, and eidos, forma.) 



The order Nematoidea includes the Entozoa whose organization 

 is the highest ; the body is cylindrical and elastic, more or less 

 attenuated at each extremity ; intestinal canal complete, provided 

 with a mouth and anus ; sexes distinct ; commonly oviparous, 

 rarely viviparous. The head is continuous with the body, very 

 rarely separated by a neck, often obtuse and sometimes edged by 

 lateral membranes (what Rudolphi has called winged) . The pos- 

 terior extremity of the body is either sharp or obtuse, often curved. 

 The male is almost always smaller than the female, and the penis, 

 which is either a single or double spiculum, frequently projects 

 externally. In both sexes the internal organs of generation (the 

 ovaries in the female and the seminal tubes in the male) are in 

 the form of long filaments, which surround the intestinal canal. 

 The generic characters are taken principally from the shape of 

 the mouth, or from the disposition of the tubercles which sur- 

 round it, the absence or presence of lips, &c. 



The genera in this order are found in all classes of animals ; 

 they inhabit almost every organ, but most frequently the alimen- 

 tary canal. 



Genus 1. Filaria. 



(Derived from filum, a thread.) 



Body long, cylindrical and elastic, nearly of equal diameter through- 

 out ; mouth orbicular. Male organ a simple spiculum. 



This genus was established by Miiller, and has been adopted 

 by Rudolphi ; the species inhabit cellular membrane in every part 

 of the body, very rarely the alimentary canal ; they are not un- 

 common in mammalia, birds and fish, they are less common in 

 reptiles ; they occur also in invertebral animals, particularly in 

 the larva of Lepidoptera, and in some Coleoptera. 



