a lesser extent the ontogeny of the individual. As long ago as 

 1866, Schneider called attention to the fact that strongyles 

 have an intestine composed of but a few cells, 18-20, there 

 being only two in a given intestinal circumference. Maupas 

 (1900) noted that rhabditids also have but few intestinal cells 

 in the adult stage, 30 being recorded in Shabdilis elegans 

 while 18 were counted in newly hatched larvae of this species. 

 Similarly Pai (1928) found only 18 intestinal cells in adult 

 Turhatrix aceli and the writers find 64 intestinal cells in adult 

 Rhabditis sirongyloidcs and 20 in first stage larvae. On the 

 other extreme we have forms such as Ascaris lumbricoides with 

 innumerable intestinal cells (about 1,000.000), forms such as 

 Heterakis gaUinae with about 12,000 and intermediate forms 

 such as Prionchiihin, Hi/strignathiis, and Metoncliolaimus with 

 about 600, 400, and 5,000 respectively. In forms with 64 or 

 less intestinal cells the most notable and obvious feature is 

 that the cells tend to be longitudinally elongate and rectangu- 

 lar (Figs. 99A-C, lOOC, 102C). When the number is 64 (Fig. 

 lOOA) the characteristic hexagonal appearance is first notice- 

 able in only a few of the cells but when the number reaches 

 128 all are hexagonal. 



The picture becomes clearer when this information is ex- 

 amined in the light of embryonic development. Martini (1903) 

 found that when 10 cleavages have occurred the definitive larva 

 is formed — an organism with a theoretic number of 1,024 cells. 

 However, there is a definite lag of cleavages in the endodermal 

 stem cell since the cells of this line actually number 16 to 20 

 instead of 128 as would be expected if no lagging occurred. 

 Comparing this information with facts concerning the somatic 

 musculature one notes that the tenth cleavage has taken place 

 in the mesodermal stem cell since 64 cells are present at hatch- 

 ing, this being the total number to be expected, as well as the 



typical number of cells in adult meromyarian nematodes. From 

 this point of view, one might say that the course of regular 

 cell division has not been fulfilled in a nematode with less 

 than 128 intestinal cells and that cell division has only pro- 

 ceeded beyond "completion" when the intestinal cell number 

 exceeds 128. 



Thus, on the basis of the number of intestinal cells, one 

 may cla-ssifj- nematodes into two groups, namely those which 

 have not exceeded the ' ' fore ordained ' ' number and those 

 which have exceeded this number. For the first condition we 

 propose the term lAigocytous while for the second condition 

 the term polycytotis may be used. However, there is a tre- 

 mendous variation in the possible number of cells in the latter 

 instance and for descriptive purposes a further division seems 

 to be advantageous. Such a division is difficult but one finds 

 a moderate correlation between the number and height of cells 

 in a cross section and the total number of cells of the intestine. 



Forms with less than 8,224 cells (16 cleavages) have more 

 or less cuboidal epithelium with a maximum of 20-;')0 cells, 

 usually of equal height, in a given circumference. Where 

 raised areas occur in the lumen they are generally due to high 

 individual cells. On the other hand forms with over 8,224 cells 

 have 100 or more in a given circumference and definite plicae 

 or villae are formed by groups of higher cells. The term 

 polycytous is arbitrarily limited to forms with the former 

 type of intestine (256-8,224 cells) while the term myriocytous 

 is introduced for forms with the latter tvpe of intestine (over 

 8,224 cells). 



Cell Char.\cter. — It has previously been noted that cells 

 in various regions of the intestine may differ in character; 

 upon some occasions specialized cells may be scattered in the 

 intestinal epithelium. Forms in which such cells are present 



Fia. 102. I.XTESTIN'AL CELLS IN THK RIUBDITINA AND STRONGYLINA 



A-C — RliahilitiH Ifirrirolit (A — Cross, C — horizontal .section of intt-s- 

 tine; B — partially dissolved .si)haerocry,stals in neutral violet); D-E — 

 PnnnurnliiiintiH HiilifUtnsjntitu ( L> — Cross, E — longitudinal section of in- 

 testine) : F-G — liliithdiaH ettstreptoH. (Cells seen in cross section, F — 



anterior. G — mid to posterior): H-.I — Dih/h'twhus tlipsari (I — longitu- 

 dinal serlinn; H & ,T — cross sections): K — Oesnphfiffostomum denta- 

 tutu (Cross section): L-M — S'tronyt/lus pdfnttitutt (L — Surface view; 

 M — isolated sjihaerocrystals) . 



102 



