Two Peculiar Actinian Lame from Tortugas. Florida. 175 



for study more specimens than any of the investigators named and that 

 my material was excellently fixed for histological examination has in- 

 duced me to give a rather detailed description of these peculiar larvae. 



CLASSIFICATION. 



As alread}- noted, Van Beneden proposed for these two types of larvae 

 the generic names Zoanthella and Zoanthina, with the express statement that 

 these names are to be regarded as provisional and that they are to be dropped 

 as soon as it is possible to refer these larval forms to any known adult actin- 

 ians. The following are the characters of these genera, according to Van 

 Beneden : 



Zoanthella: Pelagic larvEe, attaining a length of 13 mm. Body elongated, pro- 

 vided with a flagellar plate of distinct cilia, or with a vibratile fringe, extending 

 parallel to the axes of the body along the anterior median line. Twelve septa, of 

 which six are macrosepta and six microsepta, disposed as in the Zoantharix (micro- 

 type of Erdmann). Aboral pore present or absent. 



I'nder this genus Van Beneden recognized two species, viz : 



Z. semperi: Body cylindrical, with spiral torsion of median plane and vibratile 

 fringe, the latter running from one pole to the other; body not incurved on ventral 

 side at oral end ; with an aboral orifice. Mozambique Current. 



Z. henseni: Body elongate pyriform ; large end aboral, actinosome terminal at 

 small end ; body incurved on ventral side at oral end ; no aboral orifice ; vibratile 

 fringe in the upper (oral) two-thirds of body, lacking in aboral third. Guinea Current. 



To these Heath (1906) has added a third species with these char- 

 acteristics : 



Z. galapagoensis: Body spindle-shaped; ciliated fringe slightly spiral, exposed 

 cilia-bearing portion of fringe of much smaller extent than side in contact with 

 mesogloea ; body not incurved ; cilia of fringe not fused into membrane ; no aboral 

 pore. Near Galapagos Islands. 



In almost every particular the specimens which I obtained at Tor- 

 tugas and Nassau resemble Z. henseni; the only difference of note is that 

 in Van Beneden's specimens the cilia of the vibratile fringe are not closely 

 adherent into a continuous membrane, whereas in my specimens the cilia are 

 intitnately connected together in life, though they may be more or less 

 separated after fixation. Inasinuch as Van Beneden had only two pre- 

 served specimens for study it seems probable that the separation of cilia 

 may have resulted from the fixation, and that in life the cilia adhere closely 

 together, as in my specimens. The Tortugas and Bahama specimens are, 

 therefore, in all probability, examples of Z. henseni, and the fact that thev 

 are found in the Gulf Stream as well as in the Guinea Current indicates 

 their very wide distribution. 



The characters of the genus Zoanthina are indicated by Van Beneden 

 as follows : 



