(Kr. 81). In Philomiira tlie fourth and fifth Rioups of r.i(li;il 

 nuclei (K IV anil R V) aio also divideil intii two siili);i"iip>^ 

 each, Imt the niaiEinals and radials retain tlie same relative 

 piisitiiins as in Druciinciitii.K; liowever, in the latter the snli 

 ventral t;l:'"ds ( ^'iK. Td) are K'eatly redueed in size. V;inia 

 Kiiti ( IMii.'i) descM-ilied a Kenus, IcUiiinfihiiid. with a imsteriiir 

 (fl.'indular appendatle similar to that ohsei-ved in i'(mlnini( rii iii. 

 liowever a study of the histoloRV of this sirnetiire li.as not 

 lieen made. 



Philoni ma represents the ultimate in esoidiaReal );l''"'d de 

 velopment of the Draeunenloidea. This genus has the typieal 

 spiruroiiitilarioid esophagus, a fact that opens the tiuestion 

 whether or not it is eorreetl.v placed in the suborder Camalla 

 nina. .Ml three csojihageal gland orifices are located in the 

 posterior, much eidarged glamlular region of the esophagus 

 and the esophageal glands are multinucleate. The radial nu 

 clei of all six groups are arranged in triplets, i. e., all six 

 groups are subdivided; since there are three gro\ii)s of r.adials 

 in the anterior muscular part of the esophagus one would 

 .judge this part to be homologous to the anterior jxirtion of 

 the es<iphagus of CaimiUaniix : the position of the subventral 

 gl.-md orifices (Fig. 7t)) is in support of this view. The dcu-sal 

 gl.-ind orifice is shifted consider.-ibly jjosteriad in this form. 

 The esophageal glands each contain several hundred nuclei of 

 varying sizes often arranged in api)arent "constellations'" 

 such as one would expect from nuclear budding induced 

 by gigantism. Perhaps this case is analogous rather than 

 liomidiigous to that of the multinucleate glands of spiruroids. 

 In the spiruroids the many gland nuclei ajiparently arose 

 through typical division because they are approximately equal 

 in size. If Philonrma did arise separately the gigantism of 

 these glands in Draninctihis and Philomcira might be corre- 

 lated with the unequal nuclear divisions (amitosis.M in the 

 gland of Philonema. 



.'iPiRl'Rlx.v. — There are two esophageal features common 

 to the forms contained in the suborder S|)irurina, namely, 

 that the esojihageal glands are always nudtinucleate and that 

 the dorsal gland always opens in the glandular (posterior) 

 part. Esophagi of members of this group are grossly cylindri- 

 cal or divided into a short anterior muscular j)art and a wide 

 posterior glandular part. Even in forms with a cylindrical 

 esophagus these two parts are distinguishable on the basis 

 of their consistency. The gross form of the esophagus appears 

 to be of no phylogenetic significance since changes from dis- 

 tinctly "divided esophagi" to cylindrical esophagi occur 

 sporadically within groups of closely related genera. 



In all except one family the marginal and radial nuclei 

 are of the same number as in the suborder Caniallanina (totals 

 of 12 and 3(i respectively) ; in this one exccjitional family, 

 the Physalopteridae. there appears to be a ncm limited num- 

 ber of radi.-il nuclei (Fig 81) ; the radial nuclear sets usually 

 are all .subdivided, three in each group, but in some forms 

 (Fig. 81) the second, third or fourth may be partially or not 

 at all subdivided. Regardless of the gross apparent extent of 

 the glandular region, in all forms the anterior mu.scular part 

 contains only the first 12 radial nuclei and the posterior glan- 

 dular part contains 24 ladial nuclei (or more as in PhiisnJoptria 

 maxillaris) ; the anterior part does not, therefore, correspond 

 to the entire anterior part of the esophagus of CiniKiIhiiiiix. 

 Since the fifth and sixth groups of radial nuclei of Ciiiiitillaiiiix 

 a])pear to correspond to the radial nuclei of the bulb of lilinh- 

 ililix and the fifth and sixth groups of Ascnris. one would 

 conclude that the remainder of the esophageal nuclei are homol- 

 ogous to those of the corpus; since the second group of mar- 

 ginal nuclei is typically anterior to or ojiposite the third group 

 of radial nuclei, the third and fourth groups of radial nuclei 

 of Camallaniin are probably homologous to the second group 

 of radial nuclei of Rhabditis which has divided in this form; 

 hence the second group of marginal nuclei and third and 

 fourth groups of radial nuclei are homologous to the nieta- 

 corpus; if, likewi.se, the first group of radial nuclei of Hhah- 

 ililiti divided as also the first group of marginal nuclei of this 

 form (the marginals migrating anteriorly) then the honuilogies 

 indicate that whatever region contains the first and second 

 grou]) of radial nuclei in a s|iiruroid is the procorpus. There- 

 fore, we may say with a reason;ible degree of certainty that 

 the anterior muscular region of these forms is the prnriirpiis 

 and the posterior glandular region is mrldrorims and hiillxtr 

 rrflinn. 



The esophageal glands of spiruroids anrl fil.-irioids have 

 very many nuclei, varying from a minimum of about 3(1 each 

 to a maximum that can scarcely be estimated in forms such as 

 Phjixdhiptrra. The increase in nuclear number in these forms 

 has apparently [irogressed with regularity in division since 

 the nuclei arc fairly ecpial in size. 



The esoph:igeal lumen may be simple triradiate as in liirlii- 

 lurid riil(}r(iili< ii.si.s (Fig. 82), somewhat dilated but convergent 

 peripherally as in .IscarDphis or contain nuirginal "tubes" 

 as in llixiiiiiliiccrca iiiimiilirti and Diphilriai iioidi x (Fig. 82). 

 FurfheruHjre the esophageal lining may have thickened regions 

 as in MiiiiDjii liiliiiKiim ]t)itisnUinim, sometimes with distinct 

 atlacliiTicul p(]irits, or it luay be unmodified. Thus f.ar the l>os 

 silile phylogculic significance of such structures has not been de- 

 termineil but niodilii'ations ajipear to be nuist pronouni'ed in the 

 forms found in body cavities or tissues, i. e., Filarioidea. The 

 form (if the esophago intestinal valve changes from a dis- 

 tinctly triradiate shajie such as is found in Hiciiilaria to a 

 (|(U-so\'entrally flatteucil structure such as is found in Plu/.salrt/}- 

 tcnt. 



Further infoj-maliou on uucle.ar arrangement, esophageal 

 lining .'ind shape of hnnen .'iiid esophago-intestinal valve, will 

 result in substauti.al evidence hearing on the inter-relationship 

 of meudiers (d* the suborder Spi?'uriii;i. 



H. SI'KCI.ASS .\1'11.\SM1I)I.\ 



.Aphasruidians as a wijole have no single esophageal feature 

 in common. Like the subclass Fhasniidia they are divisible into 

 two ma.jor groups on the basis of the esojihagus, the first order, 

 ('hroniadorida, corresponding to the order Rhabditida, contains 

 forms in which the eso|ihagus is primarily divisible into cori)US, 

 and bulbar region, the second order, the Enoplida, contains 

 forms in which this division is not grossly apparent. 



r'H!iOM.\DORin.\. — The esophagi of members of this order 

 have three uninucleate esophageal glands; the dorsal gland 

 orifice is situated at or near the base of the stomatal region 

 (never, so far as is known, does the glaiid empty directly into 

 the stoma through a tooth) ; the subventral gland orifices are 

 at the base of the corjuis. Rei)resentatives of this order have 

 l)ecn studied by the writers (193(!). 



The suborder Monhysterina contains forms in which the 

 esophago-intestinal valve is relatively well developed, often 

 quite elongated, and dorso-ventrally flattened, or ro\inded 

 rather than triradiate. 



Of the whole Apliasmidia the representatives of the super- 

 family Plectoidea nuist closely approach the Rhabditoidea, for 

 in this group forms such as Plrctns have a rhabditoid esopha- 

 gus w^ith a well developed valve in the bulb, but unlike Rhab- 

 ditis the pro- and metacorpus are seldom apparent on gross 

 study. The lumen of the corpus terminates marginally in dis- 

 tinct tulies and the valve of the bulb works in a manner 

 similar to that of Rlinhditix. Other plectoids have an elongated 

 luilbar region without valves and in some forms the cori)Us 

 also may be quite elongate ( Lcpiolainuis) , while in others 

 < Aiinncliux), the entire esophagus may be cylindrical (Fig. .*2). 

 The musculature of the bulbar region may be reduced so that 

 this region forms an elongate glandular swelling (Camacolai- 

 inns, Anguinoidcs, AphannUumns) similar to that part of the 

 esophagus of Diljjhnchux. and in still other forms such as 

 OnchiKm nceUatum the esophageal glands may project poste- 

 riorly beyond the base of the esophagus. It would appear, 

 therefore, that not only in stylet and stomatal formatiim but 

 also in esophageal formation the Plectoidea present a parallel 

 series to the Rhabditina. In two points all plectoids are simi- 

 lar, the esophageal lumen of the corpus peripherally is termi- 

 nated by marginal tubes and the esophago-intestinal valve is 

 definitely dorso-ventral in symmetry (Figs. 83-84). 



The corpus of all forms contains four groups of six radial 

 nuclei (24) and two groups of three (or three double) margi- 

 nal nuclei (total (i or 12). The radial muscles of the corpus 

 are more or less concentered but no forms are thus far known 

 in which the lining is thickened forming attachment points. 

 As in Rhahditix in the bulbar regiim there are 12 radial and 

 (5 (or 12) marginal nuclei, the first set of 6 radials and the 

 first set of marginals forming the jirevalvar region; the suc- 

 ceeding radials are arranged in two groups of three which 

 together with the second set of marginals form the post- 

 valvar regicm. In Anuplictiix pnniidoxnx (Fig. 83) and simi- 

 lar forms with unusually well developed " tubes "" at the ends 

 of the esophageal radii the marginal nuclei of each group 

 are double, cme member of each i>air being on each side of 

 each tube, while in forms such as Camaeotaimiix prijihrrrhi in 

 which the tubes are minute (Fig. 84), no such doubling of 

 m.'ugin.'il nuclei occurs. 



Rei>resentatives of the suiierfamily .Vxonolaimoidea have 

 esophagi like plectoids except that no representative of this 

 group has a valved bulb .and no forms are known in which the 

 bulbar region is ]irincii)ally glandular through enlargenu-nt of 

 esophageal gl.-inds at expense of muscular tissue (Figs. 82 & 

 S4). The entire cscjpliagns may be clavate (Cnmrxinna. !<nhnli<- 



S3 



