442 J- " FÜIXARTON, 



36 n. g., from Nvhich the uerves to the lateral appendages arise, Fig. 33 

 — 36 nv. While the spindle-shaped interruption in the transverse 

 band remains, it is still covered by the tissues of the body-wall, 

 Fig. 3-4 /*. 0. The band has also become attached at its outer end to 

 the sides of the body, m. 6. It is attenuated both towards the sides 

 and towards the middle. The unequal contraction caused by reagents 

 makes the band assume in Fig. 34, a curved appearance , and the 

 wrinkling noticed between the lateral appendages is due to the same. 

 The spindle-shaped space still maintains a position about mid - way 

 between the centre row of nerve cells and the sides of the body. 

 Both in this and in the younger stage, Fig. 33, the long axis of the 

 nuclei are in the same direction as the length of the band. They 

 are only seen after the action of staining agents, but they form such 

 a continuous and regular transverse line from side to side that it 

 scarcely requires differential staining to mark them off from the 

 nuclei of the layers of the body-wall. When the band is complete 

 from side to side the animal shows that it is approaching maturity, 

 and the discontinuous bands are only found in immature individuals, 

 Fig. 33 nib. The cells of the band become greatly elongated till tliey 

 have all the appearance of long and narrow spindle-shaped libres, but 

 this is more noticeable in more advanced stages. 



In the fully ripe females, containing genital products ready to 

 be shed to the exterior, what was a spindle-shaped marking or inter- 

 ruption in the band in younger individuals, has now become a definite 

 opening. Figs. 35, 36 f.o. The genital clefts have doubtless arisen 

 by the parting of the muscular and epidernuil tissue of the body 

 wall, which was seen covering ventrally the interrupted space already 

 mentioned. The opening is surrounded, as Leuckart «.V Pagen- 

 STECHER noticed, by tumid or swollen lips. The median end of the 

 opening is pointed while the lateral portion is rounded. In the tissue 

 of the lips, besides muscular fibres, oval cells are seen at intervals, 

 and the two lips meet near to the outer margin of the ventral nerve 

 chord to form the connecting band (Fig. 36 mb.) to the paired opening 

 of the other side. The band becomes slightly thinner at the lateral 

 edge of the ventral chord and broadens out till it attains a maximum 

 as it crosses the central row of nerve cells, which is so characteristic 

 of I'omopteris , as other observers have already noted. A similar 

 muscular band is joined to the outer rounded end (Fig. 36 7nb.) and 

 is inserted immediately in front of the origin of the fourth and fifth 



