7. Anthozoa (incl. Hydrocorallia). C. Hydrocorallia, 25 



epithelium resembling that of the above described groove. In some cases the 

 groove is altogether absent but more frequently the lateral walls are approxi- 

 mated and thus give rise to two grooves, one ventral and one dorsal but the 

 epithelium lining the tube is the same throughout. This may be a primitive 

 condition from which the single groove of the Alcyonarian or the two grooves 

 of the majority of Zoantharian polyps may have been derived. The meso- 

 gloea of the colony increases in thickness as a result of the activity of the 

 ectoderm cells and as it increases scleroblasts budded off from the ectoderm 

 are enclosed in it and give rise to the spicules. The mode of origin of new 

 polyps in L. is described and a new set of descriptive terms applicable in 

 particular to the Alcyonacea is given. 



C. Hydrocorallia. 

 See Steinmann. 



