H. T.'ixoo: 



which varies in length, shape, and position with reference to the 

 vertical axis of the cyst. Shape, size, and proportions of the cysts 

 are highly variable; and while it can be shown statistically that 

 averages of these dimensions or of the relations between them differ 

 between species, such averages are of little value for identification 

 of small lots of cysts. 



As has been illustrated by Chitwood (195l) for H. rostochiensis , the 

 cysts of all species are made up of several distinct layers. When the 

 cysts of some species are fresh, they may be covered or partly covered 

 by the "subcrystalline layer." This is a waxy, translucent substance 

 which apparently persists for only a short time in the soil. 



The color of mature cysts is always some shade of brown. The cuticle 

 of living females may appear white, colorless, or yellow. 



The outermost layer of cysts is marked by grooves and ridges which 

 form distinctive "patterns." These vary in detail with individuals, 

 but are sufficiently constant within groups of species to be of value 

 in identification. The pattern is visible on immature females and can 

 nearly always be seen on part or all of cysts even when these are very 

 old. In certain species, the basic element of the pattern at the mid- 

 dle of the cyst is a short zig-zag line which may appear as light on a 

 dark background or dark on a light background, according to the focus 

 of the microscope (figs. 1, 8, and 26). The segments of the line are 

 straight, and the angles between them are well defined. Usually these 

 lines near the middle of the cyst show no trace of regular arrangement. 

 Near the base of the neck and around the vulva there may be parallel 

 lines (fig. 9) or wavy lines (fig. 10). The size of the elements of 

 the pattern may vary greatly, being small as shown in figure 8, rela- 

 tively large as shown in figure 26, or intermediate between these two. 

 A variation which seems rare is the network pattern shown in figure 12. 

 An occasional cyst with partly zig-zag and partly netifork pattern has 

 been seen. So far as is knotm at present, there is no constant dif- 

 ference in pattern between species in the H. schachtii group, though 

 it is possible that fine, coarse, or network patterns will be found 

 more frequently in some species than in others. 



A second type of pattern is found in the group of species which in- 

 cludes H. weissi , K. cacti , and probably a number of undescribed 

 species. This patTern has as its basic element parallel lines running 

 around the cyst at right angles to the vertical axis (fig. 13). These 

 may be interrupted at intervals by short vertical or oblique lines 

 (figs, lii and 15). Sometimes this pattern may appear somexuhat like 

 the zig-zag pattern but differs in that some trace of the parallel 

 lines always remains . 



The cysts of H. roctochiensis and H. punctata have a third type of 

 pattern. Around the ^Iva it is made up of wavy lines (fig. 19. On 

 the lower portion of the cyst, there are short, crooked lines, some- 

 times in horizontal rows (fig. 22). On the upper part of the cyst, 

 the lines tend toward the vertical, sometimes appearing as nearly 

 vertical ctriae (fig. 23). 



