176 Papers from the Marine Biological Laboratory at Tortugas. 



Pelagic larvK, body ovoid in early stages; a circular constriction, bearing flagellae, 

 divides the body into two unequal parts, an upper smaller part containing the mouth 

 and the pharynx, and a lower larger part; 12 septa are present, 6 macrosepts and 6 

 microsepts. as in the microtype of Erdmann. 



Z. iiatioiialis: Larvae longer than wide (one with 12 septa measuring 2.2 mm. in 

 length, 2 mm. in width); ciliated furrow very deep; oral part of body attached to 

 aboral by a sort of peduncle ; no ectodermal papilla near the mouth ; no canals in 

 mesoglcEa; an orifice at aboral pole. Guinea Current. 



Z. americaiia: Larvae less elongated in the chief axis (one with 12 septa measures 

 1.4 mm. long, 1.5 mm. wide); ciliated furrow less deep; ectodermal papillje present 

 near mouth; canals in mesogloea ; no aboral orifice. Beaufort, North Carolina. 



It is not possible to determine with certainty wliether the specimens from 

 Tortugas belong to either of these species; in fact it is not certain that 

 the specimens obtained by \'an Beneden and McMurrich belong to dif- 

 ferent species. In inost regards the Tortugas specimens closely resemble 

 both of these species, though in some respects they are different. From 

 Z. Iiatioiialis the Tortugas forms diiier in having no trace of an aboral 

 pore, and if Van Beneden had not made a careful histological study of this 

 form it might be doubted whether such a pore actually exists. As it is, 

 it is at least possible that such a pore represents an artifact rather than 

 a normal structure. Another difiference is found in the length of the actino- 

 pharynx; in \'an lieneden's specimen it does not extend as far inward as 

 the level of the constriction ; in the Tortugas specimens it does. The Tortu- 

 gas form dilTers from McMurrich's larva only in the lack of oral papillae and 

 of large canals in the mesoglrea at the bases of the septa. These differences 

 may be due to the fact that Mc^Iurrich's oldest larva was more advanced 

 in development than any I have examined. On the whole, then, there does 

 not seem to be sufificient ground for considering the Tortugas form as the 

 type of a new species. Numerous specimens of Zoanthina were taken at 

 Nassau, Bahamas, in April, 1907. Of these there were two dififerent kinds ; 

 one, a small yellowish form, identical with the Tortugas species, the other 

 frequently tnuch larger and of a violet color. Many individuals of this 

 latter form were as much as 5 mm. long and 3 mm. in diameter, but no one 

 of them showed any trace of tentacles. 



The larva described by Cary (1904) is evidently very distinct from the 

 forms just named, and it is doubtful whether it can be included in the 

 same genus ; in this form the circular band consists of bristles instead 

 of cilia, and it forms a ring open at one side instead of a closed one. 



Tliis summary shows that these larvae have been found chiefly on the 

 high seas in the Atlantic, Pacific, and Indian oceans. The specimens taken 

 at Tortugas were virtually from the Gulf Stream, and it is not improbable 

 that those obtained by McMurrich at Beaufort and by myself at Nassau 

 were also from this same ocean current. What the habitat of the adults 

 may be is purely a matter of conjecture. 



