ORDERS AND CLASSES OF NEMAS 215 



LAIMIA 



Nemas having a more or less distinct pharynx 



A distinction is here made among the mouth-parts of nemas, based 

 on their origin, location and method of use. Sometimes these organs 

 are labial, and sometimes they arise from elements deeper in the pharynx 

 and more closely associated with the oesophagus proper. When aris- 

 ing by modification of the labial region they are here termed odontia, 

 singular odontium. The odontia are usually of smaller size than the 

 second class of mouth-parts that arise from elements farther back and 

 more closely associated with the oesophagus proper, and called onchs 

 or onchia, singular onchium. The odontia are seldom less than 

 three in number, and may constitute a labial circlet of a dozen or more 

 elements. The onchia are almost never more than three in number, 

 and even then often only one of them is well developed. 



According as they are characterized by the absence or presence of 

 onchia, LAIMIA may be divided into two classes, the Anonchia and 

 the Onchia. The Anonchia may in turn be divided into the subclasses 

 Anodontia and Odontia, according as they lack or possess odontia. 

 There are three anodontian orders, Cytolaimia, Isolaimia and Poly- 

 laimia; and two odontian orders, Apodontia and Synodontia. Of these 

 five orders, the first three are characterized by the pharynx being 

 wholly unarmed, the pharynx of the cytolaims being a plain conoid, 

 subspheroidal, or somewhat irregular cavity, the pharynx of the isolaims 

 being mainly cylindroid or prismoid, i.e., parallel-sided, and the pharynx 

 of the polylaims being more complex and composed of two or three 

 successive chambers more or less distinctly separated from each other; 

 while the latter two orders have a pharynx armed with odontia, the 

 odontia of the Apodontia having an outward stroke, while those of the 

 Synodontia have an inward stroke. 



The second class of the LAIMIA, the Onchia, is characterized by a 

 pharynx armed with onchia or with a spear composed of amalgamated 

 onchia, and is divided into two subclasses, the Homonchia and the 

 Heteronchia, differentiated from each other by the fact that in the 

 homonchs the onchia are similar to each other and symmetrically 

 arranged and nearly always three in number, while the heteronchs are 

 characterized by asymmetrical onchia, the number of which may be 

 reduced to one. There are four orders of homonchs and two of heter- 

 onchs. The four homonchian orders are the Synonchia, in which the 

 onchia, nearly always three in number and of equal size, have an in- 

 ward stroke; the Mesonchia, composed of forms intermediate between 



