14 BULLETIN OF THE 



to the basement membrane, with which they are connected by short 

 necks or tubes (Fig. 4). The cell at this stage contains a single very 

 large nucleus, in which there is no nucleolus, since the chromatin exists, 

 as in the other cells of the hypodermis, in the form of fine particles 

 scattered uniformly through the nucleus. Later, the cell begins to sink 

 deeper into the tissue below the hypodermis, and the tubular neck 

 increases cori'espondingly in length. The cell contents become finely 

 granular, and appear to grow at the expense of the nucleus, which no 

 longer fills so completely the sac, but becomes smaller and occupies 

 the bottom of the cell (Fig. 7). In the protoplasm surrounding the 

 nucleus, there appear small, round, highly refractive particles that stain 

 deeply. These increase in number and in size, and soon become elon- 

 gated, taking on the spindle shape so characteristic of the rhabditi (Fig. 6, 

 rhb.). During these stages of formation the cell comes to lie in the 

 body parenchyma below the muscle bands, but still retains a connection 

 with the hypodermis by means of its long tubular process. The cells 

 are at length filled with rods, and the nucleus is crowded to the bottom 

 of the cell (Figs. 1, 5, and 10). 



The fully developed rods are guided to the exterior by means of the 

 tubular prolongations of the parent cell, and finally make their way 

 through the basement membrane and come to lie between the cells of 

 the hypodermis. The rhabditi, so long as they are contained in the 

 parent cell, are not hard and rigid, but possess a certain amoui>t of 

 plasticity, as can be seen by the manner in which they are bent when 

 many are packed in one cell. This plastic condition of the rods facili- 

 tates their passage through the basement membrane. I have been able 

 to find a number of cases such as that represented in Figure 8, where I 

 have shown one of the rods in the act of passing through the membrane. 

 The rods possess this pliability until they leave the deeper tissues, and 

 they attain their definite shape only after they reach the hypodermis, 

 where they become hard and inflexible. After the discharge of the 

 rhabditi. the parent cells become absorbed and disappear. 



Anton Schneider ('73, p. 87) says concerning the parent cells, "Sie 

 haben mehrere nach der Haut gehende Auslaufer, deren Epithelzellen 

 reichlich damit gefiillt sind." According to Moseley ('74, p. 119), 

 " The parent cells of the rod-like bodies are arranged beneath the exter- 

 nal longitudinal muscular layer at a tolerably even depth ; they are, in 

 spirit specimens, of an elongated oval form, with the upper extremity 

 drawn out in a point or long filament, which in some cases may be seen 

 to reach up to the basement membrane." In another place ('74, p. 120) 



