Anatomical structure of Aspidogaster conchicola. 529 



omitted the follicles and one must suppose the two longitudinal canals 

 raised to a higher plane than the ovary and testis. The transverse 

 canals may simply join onto the sides of the longitudinal canals, or 

 more frequently the latter make a bend downwards, at this point, 

 and send a little conical projection out to meet the narrow canal 

 from the yolk reservoir. The bend is sometimes so pronounced as 

 to appear as if the transverse canal had split, at its outer end into 

 a forwardly and a backwardly directed branch. The place of union 

 is approximately one third from the posterior end of the longitudinal 

 canal. All along its sides, each longitudinal canal, which is simply 

 a collecting duct, receives the openings from numerous flask-shaped 

 follicles. These lie round it on all sides as best seen in cross sections 

 (Fig. 11, 12 AG) where varying numbers, six or more, of follicles 

 may be arranged in a circle. The follicles (lobes) (Fig. 25, 30) them- 

 selves are spherical, oval or flask-shaped with a very short, wide 

 opening on one side, or a slightly lengthened neck connecting them 

 with the collecting duct. Occasionally there are two follicles to the 

 one neck. The follicles have about the same size as the neighboring 

 parenchyma cells (0,09 mm long and 0,06 mm broad, in the living 

 worm). Each is definitely limited by a distinct, thin, extensible mem- 

 brane which continues through the neck into the walls of the collecting 

 tube. On the inside of the follicular membrane can often be seen 

 small closely placed cells while those in the centre of the lobe are 

 larger. It seems probable that the yolk cells originate similarly 

 to the ova. The smallest cells as they increase in size acquire a 

 larger amount of protoplasm round their nuclei, which is gradually 

 changed over into yolk granules. In stained preparations one can 

 recognize differences in the constitution of the contents of a single 

 cell. One part stains deeper than another. Besides these differences, 

 there are in some preparations bright fat-like globules (Fig. 32). They 

 are probably transitional stages to yolk granules. They remain un- 

 stained, two or three in a single cell. Centrally situated is a large 

 nucleus with scattered deep-staining nuclein. The yolk-cells, as found 

 completed in the ducts or reservoir, are spherical or angular according 

 to the pressure and each bounded by a membrane. 



On the inside of the walls of the longitudinal, as well as of all 

 the other ducts, are scattered nuclei. It is only rarely one gets a 

 glimpse of the collecting ducts, as they are so thickly surrounded by 

 non-transparent follicles that, under pressure, flatten out and cover 

 the greater part of the space. Sometimes, though, may occur cases 



