eal purposes the term globule will be restricted to those inclu- 

 sions which are known to be nonbirefringent and appear as 

 bright circles in dark field illumination, i.e. fats and proteins. 

 The term sphaerocriistal is restricted to inclusions known to 

 be birefringent, while sphnrroid is applied to strongly refrac- 

 tive nonbirefringent or apparentl.v nonbirefringent bodies, 

 and granule is reserved for moderately or weakly refractive 

 bodies of unknown optical activity. It will appear obvious 

 that weakly birefringent substances such as gypsum may easily 

 be classified as sphaeroids pending critical study. 



The function of gypsum, sphaeroids, and granules is for 

 the most part unknown. Sphaerocrystals of gypsum were seen 

 to be thrown out or "excreted" from the cells of Ascaris 

 and Slrongylus. The yellowish brown sphaeroids of Jthahdiiis 

 and Ironus were also observed to be eliminated from the in- 

 testine (Fig. lOoR). 



(i) INTESTINAL PARASITES 



Protozoan parasites are apt to occur in the intestinal cells 

 as well as in other organs of nematodes and might easily be 

 confused with cell inclusions or degenerating cells. Jlicoletzky 

 (1922) described sporozoan parasites of the intestinal wall 

 of Dorylaimus carteri and Plectuf: cirraUt.i, and Kudo and 

 Hetherington (1922) described a microsporidian named Thrln- 

 hania renifonnis from the intestinal epithelium of Mastophorus 

 muris. The writers have encountered similar forms (Fig. 

 103C) in the intestine as well as the musculature, gonads, and 

 chords of Spironnura affine. It is sufficient, for the present, 

 to merely call attention to their existence. Many protozoan 

 and fungous parasites of nematodes have been described and 

 such information will be presented in a later part. 



D. COMPARATIVE MORPHOLOGY 



Up to the present time no consistent attempt has been 

 made to record, much less present, specific information regard- 

 ing the intestine in the various groups of the Nematoda. All 

 workers recognize various impressions upon which they may 

 have an "intuition" as to the group to which a nematode 

 may belong. Whenever it is possible, in morphology, to re- 

 duce these .sensory impressions to words, it invariably con- 

 tributes to our understanding of relationships and to the trans- 

 fer of knowledge from one worker to another. The present 

 writers must of necessity deal in terms of examples. B.v giv- 

 ing a sufficient number of examples, it is hoped that a skele- 

 ton outline may be provided around which others can build a 

 structure of some value. 



Eltnbdilina. For the members of the Rhabditina we have 

 the observations of Maupas (1900), Cobb (1914), Goodey 

 (1930), and Giovannola (1936) as our only direct attacks on 

 the problem, but numerous observations from the time of 

 Biitschli, preserved chiefly in the form of drawings, serve as 

 a foundation upon which we may build. 



The Rhabditina may be characterized as oligocytous, homocy- 

 tous, and isocytous with the excciition of the Rhabdiasidae, 

 Drilonematidae, and Allantonematidae, which appear to be 

 wholly or in part polycytous. Rhabdilis (Fig. 3, lOOA, 101, 

 102.\-C), Turhatrix, and Diploganler retain the simple uninu- 

 cleate condition in the intestinal epithelium. In these forms 

 the cellular outlines are distinct and quite often emphasized 

 by the absence of cell inclusions. The intestinal lumen tends 

 to be flattened; the cells alternate, giving a zig-zag appear- 

 ance in lateral view. Free-living stages of the Rhabdiasidae 

 are also oligocytous, and in general quite similar to BhabdUix, 

 while the parasitic adult is very definitely polycytous, the cells 

 cuboidal (Fig. 102F-Ct). Ventricular and prerectal regions 

 arc almost alwa.vs differentiated from the remainder of the 

 intestine through absence of, or marked diminution of, cell 

 inclusions. The intestine cells of many species of Sliabditix 

 contain birefringent sphaerocrystals of rhabditin, but this 

 substance has not been identified in an,y other members of the 

 suborder. Si)haeroids, apparently nonbirefringent or weakly 

 birefringent, are very noticeable in the para.sitic female of 

 Shabdias but these are of the insoluble t.vpe. Anteriorly the 

 intestinal circumference consists of about 12 cells, very low, 

 containing few or no inclusions. In the mid-region there are 

 six to eight somewhat higher cells containing a moderate num- 

 ber of small sphaeroids, numerous larger basophilic globules 

 and small basophilic granules (Fig. 102F), while posteriorl.v 

 the sphaeroids are larger, more numerous, and the basophilic 

 bodies minute and numerous (Fig. 102G). In these forms 

 the sphaeroids are a deep red-brown in color. 



Maupas (1900) noted that in some species of h'habdilis 



birefringents are absent. In such forms he found "albumino- 

 fatty" globules to be more prevalent. 



Cephalobids are usualh- described as having an intestine 

 composed of two series of cells (rows). Though the lumen 

 is dorsoventrally flattened and often appears zig-zag, as in 

 Bhabditis, no cell walls are distinguishable in sectioned Pana- 

 grolaimus siibelongaius (Fig. 102E). The nuclei are near 

 the lumen, two to six, and usually four, in a given circum- 

 ference, with a total of about 210. Since disappearance of 

 cell walls occurs in the fourth stage larva, at the same time 

 as nuclear division (there are about 20 uninucleate cells in the 

 third stage larva), it seems best to interpret this form as 

 primarily oligocytous, secondarily polynucleate and/or syncy- 

 tial. Perhaps polynucleate cells will eventur.lly be distinguished 

 as in tylenchids. The cephalobid intestine in section is charac- 

 terised by its large faintly basophilic globules, scattered brown- 

 ish shells, and large empty spaces which presumably were 

 filled with fatt.v substances. 



The Tylenchoidea present a picture in contrast to the Rhab- 

 ditoidea when the intestine is considered. Although Debray 

 and Maupas (1896) were able to distinguish 16 cells forming 

 the intestine of Ditylenchus dipsaci in the fourth stage larva, 

 distinct cells have seldom been observed in the adult members 

 of the Tylenchidae. The intestine appears as an opaque mass 

 of large globules, very beautiful in dark field illumination, 

 but not visible in polarized light. This material is of a fatty 

 character. Sections of D. dii)saci and Aphrh nchoidcs parie- 

 tinus fail to show clear evidence of cell walls (Figs. 102H-J) 

 in the adult stage. In dissected specimens the large quad- 

 rinucleate cells are seen (Fig. lOOC). The cytoplasm is highly 

 vacuolate due to the removal of fats, Basophilic globules are 

 also seen in sections, but these appear to be very erratic in 

 disposition. In D. dipsaci the lumen is dorsoventrally flat- 

 tened anteriorly and zigzagged posteriorly (Fig. 102H-.1) ; .56 

 nuclei were counted in one specimen. In A. parictinus the in- 

 testine is quite similar except that its sides in the mid-region 

 tend to be more nearly equal and tend to surround the gonads. 

 In this form a maximum of two nuclei has been observed in 

 one section and on one side of the intestine. It is notable 

 that the lumen is relatively much smaller in tylenchids than 

 in rhabditoids, and the bacillary layer relativel.v shorter and 

 more compact. Apparently we have no increase in the number 

 of intestinal cells, 16, between hatching and adulthood. In 

 Chondronema passali, the only representative of the Allan- 

 tonematidae studied, the intestine is definitely polycytous, there 

 being four to six hexagonal cells in a circumference. The cells 

 are filled with fat globules as in the tylenchids. Unlike the 

 latter, however, no bacillary layer appears to line the round 

 intestinal lumen. The lumen contains a glassy-appearing sub- 

 stance, possibly of protein nature, which is slightly basophilic 

 and apparently represents partially digested body fluid from 

 the host. Aside from the presence of a few birefringents 

 (nature unknown) in the posterior end of the intestine of 

 Chondronema, there is no known case in which either ventricu- 

 lar or prerectal regions differ from the mid-region in members 

 of the Tylenchoidea. 



Strongylina (Figs. 99 & 102). The Strongylina as a group 

 appear to be oligoc.vtous or low polyc.vtous and the cells are 

 polynucleate as noted in Strongylux by Schneider (1866), 

 Looss (1901) and Quack (1913') and in Anci/lnstoma hy Looss 

 (190.5). Other representatives of the same suborder (Ste- 

 phayiurus, Oesopliagostomum, Ostcrtagia, Lnngisfrinia, Mita- 

 strongyhis and Dictyocaulus) examined liy the writers exhibit 

 the same characteristics. The intestine consists of two rows 

 each of 10 or more cells, each cell containing 10 to .500 nuclei. 

 The smaller numbers, 10 to 20 nuclei, occur in members of 

 the Trichostrongyloidea. In such forms as Ostcrtagia there 

 are two rows of nuclei in each intestinal cell, four in an in- 

 testinal circumference while in Trichostrongylus instabilis 

 Looss (189,5) found each of the two cell rows of the intestine 

 to contain a single row of nuclei. About 40 to 50 nuclei are 

 present in an intestinal cell of Ocsojdiagostomum, 500 in one 

 of Sirongylus while no reliable estimate has yet been made for 

 Melaxlrongyliis. The sliajie of the lumen is quite diverse, be- 

 ing dorsoventrall.v flatteucd in Osti rtngia, irregular due to 

 longitudinally folded walls in Stcpliaiiurus, or rounded to 

 ovoid in Oesopliagostomum and Mclastrongylus. A thick, 

 compact liacillary la.vcr resting on a well ileveloped subbacillary 

 layer is characteristic of the Strongyloidea. Wetzel (1931) 

 and Lueker (1935, 1936, 1938) have "made use of the specific 

 intestinal cell ciuistancy of the third-stage larvae of horse 

 strong.vles as a means of dift'erentiating the species in this 

 stage. Thus Wetzel found two rows of eight long subtriangu- 

 lar cells in Strongylus equinus, two rows of ten cells in S. eden- 

 taUis, and two rows of 16 cells in iS'. vulgaris. Trucker found a 

 total of only eight cells in the intestine of Cylieodontophorns 



106 



