THE ANATOMY OF PENTASTOMUM TERETIUSCULUM. 43 



in P. subuliferum, where apparently they are very similar 

 to those examined by Stiles^ in P. proboscideum. 



In the young form the two oviducts arise from the anterior 

 end of the ovary^ the space in which is directly continuous 

 with that of the oviducts. The walls of the ovarian and ovi- 

 ducal tubes are at first precisely similar in nature, being com- 

 posed of somewhat cubical cells with distinct spherical nuclei 

 (figs. 57 and 58). In fact, at this stage these parts may be 

 described as having the form of a ring around the alimentary 

 canal, the mid- dorsal portion of which is prolonged back- 

 wards. In such forms as the Phalangidse a ring is present, 

 and the greater part of its walls form ova ; whilst in the Pen- 

 tastomum the formation of ova is confined to the backward 

 growing, median, dorsal portion, whilst the two halves of the 

 ring form oviducts, and unite together to form a common 

 median part ventrally as they do in the Phalangidse. 



As the animal grows, and before eggs pass down, the cells of 

 the oviduct walls become more columnar (fig. 56). External 

 to them is a layer of material of the nature of connective 

 tissue, and not containing muscle-fibres. 



In the mature form the two oviducts pass off from the 

 anterior end of the ovary, clusters of ova lying on the upper 

 surface immediately anteriorly to their origin, there being 

 thus no free portion of the ovarian tube in front of the most 

 anterior clusters of ova such as Leuckart describes in P. 

 taenioides. 



They then pass downwards and forwards, not encircling, but 

 passing right through the middle of the hook-gland on either 

 side (figs. 22 and 24). Having traversed the gland, each one 

 lies to the side of and immediately behind the nerve mass. 

 At this part of their course they run straight downwards, 

 enclosing between them the two large posterior nerves (fig. 

 60). Turning backwards below the level of the nerve mass, 

 they unite together to form a slightly swollen portion (figs. 

 40, 41, Co, Od. 1), which opens in the median line into a 

 short tube with strongly muscular walls {Co, Od. 2), which lies 

 ' Loc. cit., p. 138. 



