with 01- without a i.listiiu-tly si't off bulbar region (Ascaii'lia 

 and Ascarix, Toxiicara and Contracaeciim, etc.). It is in the 

 latter group that we have the outstanding diversity of the 

 su])erfaniily. While the liulbar region is always distinct in 

 the larva when removed from the egg it may totally disappear 

 from the standpoint of gross examination during later stages 

 in its development (Ascaridia, Ascaris. To.r<iscaris, etc.)- In 

 other forms it remains grossly unmodified but becomes rela- 

 tively smaller due to the disproportionate increase in length 

 of the corpus (To-rornra) and in some it becomes elongated 

 forming a short cylindroid glandular region (Anisal-is) . Forms 

 which retain a bulbar region often have one or more posteriorly 

 directed bulbar appendages {Contracaeciim, M'idticaeciim) . 

 The internal structure varies fully as much as the gross ap- 

 pearance and its variations will be dealt with separately. 

 Ascaridoids with a valved bulb invariably have marginal 



"tubes'' in the legion of the corpus and concentrated radial 

 fibers but the esopliagoal lining is without thickened attach- 

 ment points in all forms. 



Meroniyarian forms such as cosmocercids and kathlaniids 

 have approximately the same nuclei as are present in rhabdi- 

 toids and oxyuroids (one group of three large marginals and 

 two groups of six large radials in the corpus; two groups of 

 three marginals, one group of six radial and two groujis of 

 three radials, and three ghuul nuclei in the bulb). Polymyarian 

 forms, such as heterakids and ascaridids show evidence of ad- 

 diti(jnal cell division in the esophagus, for in heterakids there 

 is an additional group of six radial nuclei in the procorpus 

 making a total of 30 radials and the subventral esophageal 

 glands are each binucleate. In ascarids there are .3(5 radials 

 and 12 marginals, the additional nuclei (six radials and three 

 marginals) being situated anterior to or opposite the orifice 



Pios. 77-SO 



Di.'igranis .sliriwing distriljution of nuclei in tlie esophagi of Metn- 

 xtraniiyUix etoni/afn.i (77), Op.snphanostitmum dfntalum (78), Leidj/- 



neiiia iii>iii'inliciilnhiiii (79), iind Ueteiakin j/nHi'inif (HO), .\fter (_'hitw. 

 & Cliitw., ,1. Wnsli. ;\cml. He. 



80 



