PREVIOUS INTERPRETATIONS OF CNIDARIA 



187 



hydranth a contour ot the surface of the intestinal epithelium 

 which resembles that of folds; this is not, however, due to a 

 genuine formation of folds but rather to the tact that epi- 

 thelium cells grow in unequal lengths which leads to the 

 formation of longitudinal stripes. The last traces ot the former 

 longitudinal folds can be found in buds and occasionally in 

 the fully developed hydranths (see Fig. 34 with the transverse 

 sections ot the hydranth oiClava squamata and of the manubrium 



Fig. 34. Transverse sections of the oral region of two hydrozoans 

 to demonstrate the false gutfolds. A, Hebella parasitica. B, medusa 

 of Obelia sp. (after Hadzi). 



of an Ohelia sp.). We think it unimportant whether there is a 

 participation of the mesenchyme in these last traces of longi- 

 tudinal folds or not. On the other hand, the intestinal diverti- 

 cula which had grown into tentacles have been preserved till 

 the very end, regardless of whether these tentacles have re- 

 mained hollow or whether they have become secondarily solid 

 as can be observed in scyphopolyps and very frequently in 

 hydroids. 



It is interesting to observe the behaviour of the gastral 

 cavity during the period when Scyphozoa began to form 

 medusae, and the later similar development which took place 

 in Hydrozoa independently from the former. We can immedi- 

 ately state that this development has led to conditions that 



