Plate XVI. 



Fig. 51. Obelia dubia. 



A. Natural size. 



B. Portion of stem showing hydrothecae. 



C. Gonophore. 



Fig. 52. Obelia jragilis. 



A. Natural size (After Calkins). 



B. Portion of hydrocaulis (After Calkins). 



C. Hydrotheca and hydranth (After Calkins). 



Fig. 53. Obelia gracilis. 



A. Natural size. 



B. Portion of stem showing hydrothecae. 



C. Gonophores 



Fig. 54. Obelia griffini. 



A. Natural size. 



B. Portion of stem showing mode of branching and hydrothecae. 



C. Gonophore. 



Fig. 55. Obelia longissima. 



A. Natural size. 



B. Portion of stem showing hydrothecae, gonophore and mode of branching. 



