THE GENUS COLOBOCENTKOTUS. 33 



rence is not limited to the ambulacra near the sphasridia, nor are they limited 

 to the ambulacra. They are found both in the ambulacral and iuterambulacral 

 areas and on the actinal as well as the abactinal sides. 



I can only o£Eer suggestions as to the nature of the cystacanths. I have no 

 observations of any value regarding their function. They may be modified sac- 

 bearing spines such as are found among the Echinothuriae or modified pedi- 

 cellarise in which the glands have developed into the glands of the cystacanths 

 at the expense of the valves. 



