nuclear arrangement and gland orifice positions in the posterior 

 swollen region. The nuclei correspond to those of the posterior 

 part of the camallanid esophagus. 



Esophagi of dracunculoids were studied b.v Jagerskiold 

 (1894), zur Strassen (1907), Mirza (1929), Hsii (1933), and 

 Yamaguti (193.5). In gross features the esophagus may be 

 cylindrical as in Micropleura, clavate or fusiform as in Philo- 

 metra, divided into a short narrow anterior muscular part and 

 a long wide posterior glandular part as in Phikinema, Draciin- 

 ciiliis and Avioserpens. In DraciinciilKS and Ai^ioserpens the 

 glandular region is constricted in the latitude of the nerve 

 ring (Fig. 76). In Draciinculii.t, Avioserpens and Philometra 



y^ 



yj~p 



<=> 



the anterior end of the esophagus takes the form of a sub- 

 globular swelling but does not do so in PhUoncma and Micro- 

 pleura. 



The radial and marginal nuclei in DraciincKliis, Avioserpens 

 and Micropleura follow the same arrangement as in Camallanus, 

 R I and E VI being divided groups. All these nuclei are also 

 in the same position relative to the level o'f the orifice of the 

 esophageal glands. In Uracu7i.eulus and Avioserpens the region 

 posterior to the constriction at the nerve ring corresponds to 

 the posterior part of the esophagus of CamaUanus ; in the two 

 former genera an additional peculiarity is observed ; the dorsal 

 esophageal gland and its nucleus are tremendously enlarged 



voiy 



RiCTULARIA 



ASCAROPHIS PHYSALOPTERA OElSMIOOCERCtLLA MONOPETALONEMA OiPLOTRI AENOIDES 



SPHACROLAImuS SIPH0N0LAIMU5 



Fid 



Diagrams of esophagi; including representiitivi^s of the 

 Spiruroidea (Rictularia to Phyaaloptera) , PMIarioidt-a (IJps- 

 midocerceUa to Diplotriaenoides), Plectoidea (Plertus to Annn- 



OESMOLAIMUS THERISTUS 



rhuff), Axonolaiinoidea (Axoiwfniinus) , Chroniadoroidea (Para- 

 cnnthonchus, Tripf/louies) , Monhysteroidea (Sphafntlaiwns to 

 Theristu8) . Original. 



82 



