Fig. 106 



Ironua tenuicaudainti , (Note specialized intestinal cells containing large globules, 

 also small polyhedral crystals in ordinary intestinal cells). After Cobb. 1918, Con- 

 trib. So. Neniat. 7. 



iron salts a.s the chief cell inclusions of an oncholaimid. 



The number of dorylaimoids of which the intestine lias been 

 studied is inadequate. Members of the Dorylaimidae all seem 

 to be polycytous but the number of cells in an intestinal cir- 

 cumference varies from four to 20. Anteriorly the baeillary 

 layer is highest in the ventricular region and posteriorly a 

 conspicuous change is notable in this layer in the prerectum. 

 Throughout ventricular and mid-regions the cells contain yel- 

 lowish brown non-staining sphaeroids (appearing as shells in 

 section) while these structures are absent in the prerectum. 

 The latter is set off as a distinct section of the intestine in 

 the Dorylaimidae (Figs. 20-21) and Leptonchidae and may 

 even be subdivided into two distinct units in Actinolaimus. 

 Leptonchus resembles dorylaimids in general but differs in 

 that the number of intestinal cells is smaller ( foligocytous) 

 and the cells contain massive basophilic globules. Nothing is 

 known concerning the intestine of the diphtheroiihorids aside 

 from the fact that they have no prerectum. 



The intestine of the Mermithoidea has been given more at- 

 tention than that of other groups because, as was early recog- 

 nized, the peculiar nature of the intestine constitutes one of 

 the major characteristics of the group. Schneider (1860) first 

 recognized that the solid mass of tissue which Meissner (1853) 

 called the ' ' Fettkorper" corresponds to the mesenteron of 

 other nematodes. The work of Meissner (1S53, 1856), Schnei- 

 der (1860), Rauther (1906, 1909), Hagmeier (1912), Steiner 

 (1933), and Christie (1936) makes it possible to characterize 

 the mermithid intestine as an organ of food storage in which 

 the larva, during the parasitic stage, stores the nutrient mat- 

 ter on which it draws throughout adult life and reproduction. 

 In order to meet these re((uirements the intestine grows an- 

 terior to the base of the esophagus, regularly reaching the level 

 of the nei've ring. Rauther (1909) observed a lumen (Fig. 

 107F) in the anterior part of the intestine of Mermis sp. and 

 interpreted this part of the intestine as a caecum. Steiner 

 (1933) stated that in some mermithids the trophosome has an 

 axial cavity and a wall of polynucleate cells, while in others 

 the axial cavitj' disappears but the polynucleate cellular condi- 

 tion persists, and in still others the cell walls disappear form- 

 ing a syncytium. Rauther found that the intestine of Hexa- 

 mermis albicans consists of two longitudinal rows of cells each 

 containing 10 to 15 nuclei in the adult stage while the writers 

 found the intestine of Agamcrmis dccaiidata (Figs. 107A-C) 

 to be four to 10 cells in circumference and each cell to contain 

 22 to 25 nuclei. The total number of cells in these forms ap- 

 pears to fall within the upper limits of polycyt.v. In Hi/- 

 dromermis sp. the nuclei are relatively' larger (Fig. 107E) and 

 apparently less numerous than in the jireviousl.v mentioned 

 forms but unfortunately no exact information is available. 

 Large vacuoles containing crystals or crystal aggregates have 

 been observed in several mermithids in all stages from the 

 preparasitic larva to the senile adult; these crystals accumulate 

 with age, becoming a conspicuous feature of specimens after 

 reproduction has ceased. The increase in crystals and vacuoles 

 coincides with diminution of intestinal globules. Rauther 

 (1906) compared the crystals with uric acid but was unable 

 to obtain an unmistakable murexide reaction. Ccmcerning the 

 globules of nutritive reserve, the following observations have 

 been made on Apaviermis dccaudata: Sections of young para- 

 sitic larvae contain onl.v a few basophilic globules in a rather 

 dense cytoplasm (Fig. 107B) ; the larvae at emergence and 

 the young adults are literall.y packed with such globules in a 

 vacuolate cytoplasm; the cells of specimens in the emerging 

 larvae and adults are filled with colorless, oily appearing glo- 

 bules (whence the name fat bod.y) ; according to Chitwood 

 and Jacobs (1937) onl.v a small proportion of these globules 

 is fat, the great ma,iorit.v being protein. 



The superfamily Trichuroidea is typically myriocytous, ani- 

 soc.ytous, homoc,ytous and the intestinal cells arc uninucleate. 

 Villus formation in Trichiiris is uniform, the subpolygonal 

 units (groups of cells) causing much the same appearance as 

 large individual cells in surface view; from this standpoint 

 tliere is distinct parallelism with O.riiuri.i (Fig. 103E). Ac- 

 tuall.v each unit is comjiosed of 50 to 100 tall narrow cells. 

 The l)acillar.v layer is fpiite liigh in the mid region and the 

 basal layer is unusually thick. Reddish-brown sphaerocrystals 

 are present throughout the mid-region of the intestine. 



The intestine of the dioctophymoids is much like that of the 

 trichuroids, differing only in that the bacillar.v layer (Fig. 

 lfl5R) may reach a height nearly equal to that of the cell 

 proper. The sphaerocr.vstals are localized on the side toward 

 the lumen and villi are not uniform. 



110 



