142 A. OKA. 



this chamber, where the mouth is situated, the cells of the inner wall 

 are prismatic while elsewhere they are flat. 



We now recognize all the parts that we have seen at a certain 

 stao-e of intrastatoblastic development. The lophophore with its 

 tentacles, the nervous system and the intestine, all develope just in 

 the same way as described in the previous chapter. One im- 

 portant difference exists in this, that in the one case the lining 

 epithelium is produced from cells of granular mass, while in the other 

 it is the result of the increase in extent of the same layer of the 

 mother cystid. It will be noticed from above statements, that the 

 entire inner layer of the alimentary tract is derived from the solid 

 knob sunk in from the outer layer of the endoeyst. The hollow 

 process (the intestine) sent up from the stomach meets with and 

 opens into a pit sent in from above outside the tentacular area, on the 

 side turned toward the centre of the colony. The lophophornl arms 

 of every individual always project toward the anal side of the poly- 

 pide ; consequently they are nil directed toward the centre of the 



colony. 



While new polypides are thus being developed, their cystids are 

 also growing in size, and some cells of its lining epithelium gradually 

 o-ive rise to the muscular layer. At tirst, when the young polypide 

 is still represented by a simple sac, the portion of the mother cœnœ- 

 cium arouud its orifice is only slightly elevated above the rest of the 

 wall, but as the growth of the polypide advances, it becomes more and 

 more prominent, growing in such a manner as to form at last a cell 

 for the young polypide. 



The retractor muscles of the polypide begin t(^ appear when the 

 bud is still a simple sac, shortly after the formation of the rudimentary 

 funiculus. At the point of junction of the rudimentary polypide and 

 the cœnœcium, some cells of the lining epithelium becomes difteren- 



