30 George T/wiiias Hargitt 



Ectoderm g-radually surrounds the column to form the tentacle. 

 Amitotically dividing nuclei shown. X6oo. 

 Figs. 25-31. Tiihnlaria tenella. 



Figs. 25, 26. Early stages in the evagination of the entoderm 

 to form the proximal tentacle. X6oo. 



Fig. 27. Evagination of the entoderm complete and the ecto- 

 derm folding around the entoderm to cut off the tentacle. X500. 

 Fig. 28. One proximal tentacle cut-off and another with the 

 entoderm entirely surrounded by ectoderm but not yet separated 

 from the hydranth body. X500. 



Fig. 29. Longitudinal section through the developing proximal 

 tentacle, showing the evagination of the entoderm and the for- 

 mation of the tentacle. X6oo. 



Fig. 30. Entoderm cells being forced away from the enteric 

 cavity to form the entodermal column of the distal tentacle. 

 X600. 



Fig. 31. Entodermal column of distal tentacle separated from 

 the entoderm layer and the ectoderm beginning to surround it. 

 X600. 



Figs. 32-43. Tnhnlaria larynx. 



Fig. 32. Proximal tentacles separated from the hydranth body, 

 others in the process of separation. In one tentacle the ento- 

 derm is not completely surrounded 1)y the ectoderm. X6oo. 



Fig. 33. Earlier stages in the development of the proximal ten- 

 tacles. Entodermal column nearly complete, and the ectoderm 

 just beginning to surround it. X6oo. 



Figs. 34, 35. Very early stages in the development of the proxi- 

 mal tentacles, only a few cells pushed away from the enteric 

 cavity. X6oo. 



Figs. 36-38. Early stages in the formation of the distal ten- 

 tacles, the entodermal column shown in different stages of de- 

 velopment. X6oo. 



Figs. 39, 40. Entodermal column being surrounded by ecto- 

 derm to complete the tentacle. X6oo. 



Fig. 41. Entodermal column, entirely outside of the entoderm 

 layer, being surrounded by ectoderm. X6oo. 



Fig. 42. Completion of the process shown in Fig. 41. X^oo. 



304 



