No. 44I-] 



CORY.IfORPHA J' END ULA AG. 



these cells are numerous large thread cells. The entoderm con- 

 sists of large irregular polygonal cells which entirely fill up the 

 axis of the tentacle. Toward the distal end, the entoderm cells 

 become fewer and larger, their boundaries stretched transversely 

 across the tentacle in longitudinal section, thus giving it a 

 peculiar septate appearance. 



The ectoderm and entoderm are separated from each other by 

 a thin supporting lamella, the mesoglcea, which also separates 

 the two layers of cells in other portions of the hydroid. 



Origin and Development of the Medusa. 



The medusoids in this species are found at the extremities of 

 a number of hollow branched peduncles. These peduncles are 

 from fifteen to twenty-five in number and are arranged in two 

 circles about the hydranth just above the ] 1 set of ten- 



tacles. On the same specimen will usually be found medusoids 



ones appear at the distal 



The peduncles Upon «iitTfrom the^odLm ,! ; i, entoderi 



which the Medusae are 



borne are simple hollow outpushings of the hydranth 

 composed of the same layers — ectoderm, entoderm an 

 gcela. In their development the medusa buds present es: 



Tubularije. They begin as simple evaginations of the 

 the penduncle. (Fig. 8.) By a proliferation of the e 



