JIM 



MEDUSAE OF THK WORLD. 



and Ceylon, in the Pacific and Indian Oceans. It is common only near coasts, not being a 

 creature of the open ocean. It appears to be tar more abundant off the coast of America than 

 in European waters. I found it only occasionally at Naples during the winter of 1907 08. 



The development has been studied by MetschnikofF. The early stages are described for 

 the Mediterranean L. cniciata. The egg is 0.18 mm. in diameter and is laid between 4 and 5 

 in the afternoon from November to December. Segmentation is total and equal; and an oval, 

 hen's-egg-shaped, ciliated, one-layered blastula is formed. Sometimes one sees a slight tem- 

 porary invagination at the narrow hinder end of the blastula, but this is not the beginning of the 

 formation of the entoderm. The entoderm on the contrary is formed from numerous cells 

 which migrate individually into the large central segmentation cavity from the hinder end of 

 the hlastula. The resulting planula swims about for a time, but finally it attaches itself and 

 becomes a creeping, root-like, slightly branched hydrorhiza. from which there arise unbranched 

 polypites "resembling Cuspidella humilis or Cuspidella costata Hincks." 



The hydrotheca is long and subcylmdncal, and the margin is provided with sharp-pointed 

 teeth, and the polypite may withdraw within the hydrotheca and close the opening by the 

 folding together of these teeth. The polypites have flaring, open, urn-shaped penstomes, 

 below which there is a zone of jolong, slender, filiform, nematocyst-studded tentacles, all of 

 about the same length. 



Browne, 1907, states that Miss M. Delap, of Valencia Island, off the southern coast of 

 Ireland, maintained a colony of Cuspidella costata Hincks alive, and obtained from it young 

 medusa; which resemble the youngest stages of Laodicea calcarata found in the Ocean. It is 

 probable, therefore, that the hydroid described by A. Agassiz, 1865, as I.afira calcarata and 

 which he believed to be the nurse of LarjJicea is not such. It lacks the toothed operculum 

 found in Cuspidella and the margin of the hydrotheca is simple and entire. The direct 

 embryological evidence demonstrates that the hydroid of Laodicea is CuspiJellti Hincks. 



Tabular Synopsis of the "dinettes" of Ltiotliceii cruciiitn. 



