CONTEIBUTION TO KNOWLEDGE OF RHABDOPLEURA. 647 



of the tubarium is not represented. A polypide stalk (gymnocaulus) is seen 

 lying freely in the cavity of the tubarium, whilst two pectocauli are embedded 

 in its floor (due to bifurcation and formation of two branches, or else to the 

 pedicle of a polypide). Letters as in Fig. 9, with the addition of N, polypide 

 stalk in transverse section. 



Pig. 11. — Transverse section of same axis as in Fig. 9, at a point a little 

 posterior to that given in Fig. 9. The hinder part of the abdomen of the 

 polypide is cut a little obliquely and transversely so as to avoid the intestine, 

 whilst the polypide stalk is seen as a separate piece. Letters as in Fig. 9. 



Fig. 12. — A section of the same polypide as that seen in Fig. 9, taken at a 

 point in front of that section, n. Body cavity, o. The thick columnar epi- 

 thelium of the thoracic region, 'p. Mesoblastic cells traversing the body cavity. 



Fig. 13. — A section between Figs. 9 and 13. h. Intestine, i. Stomach. 

 m. Body cavity, -p. Mesoblastic cells. 



N.B. — Figs. 12 and 13 should be turned upside down for comparison with 

 Fiff. 9. 



