174 Papers from the Marine Biological Laboratory at Tortugas. 



seem to adhere into a plate or membrane, as in tlie case of ctenophores, but 

 after being fixed and sectioned they are frequentlv found separate. 



In one type of larva (fig. i) this band is longitudinal, extending from 

 the mouth-opening along one side of the body through about two-thirds of 

 its length ; the body itself, in this form, is pear-shaped, the mouth being at 

 the narrower end. In the other type (fig. 2) the ciliated band is circular 

 and surrounds the body about the level of the inner end of the pharynx ; at 

 this place the body is deeply constricted, the cilia arising from the bottom 

 of this constriction. 



The first type was originally described by Semper (1867) and it has 

 since been generally known as " Scmper's larva." He found it near the 

 Cape of Good Hope in the Mozambique Channel and on the coast of 

 Java. The second type was also observed by Semper, but was insufficiently 

 described by him and was supposed to be only an earlier stage in the 

 development of the first type. 



Subsequently E. Van Beneden (1890, 1898) found two specimens of the 

 first type of these larvae and one of the second in the material brought back 

 by the Plankton expedition of Hensen ; the former came from a region just 

 .south of the Cape Verde Islands, the latter from the Guinea Current, 

 ^'an Beneden pointed out the resemblance of these larvjE to the Zoanthese 

 (microtype of Erdmann, 1885) '" that, in common with this group, these 

 larvae possess a pair of perfect ventral directives, a pair of imperfect dorsal 

 directives, and between the.se on each side two pairs of mesenteries, the 

 dorsal member of each pair being perfect and the ventral member im- 

 perfect. \^an Beneden made a careful study of the morphology and his- 

 tology of these larvje, reference to which will be made later. He proposed 

 for these zoanthid larvae, the adults of which are unknown, the follow- 

 ing provisional names : For type I with the longitudinal band of cilia, 

 the generic name Zoanthelia: for type II with the circular band, the generic 

 name Zoanthina. 



McMurrich (1891) has also described a larva of this second type, 5 

 specimens of which were collected by the aid of the surface-net at Beau- 

 fort, North Carolina. He was unable to determine the adult form to which 

 this larva belongs, but he agrees with Van Beneden that it is the larval stage 

 of a zoanthid. 



Still more recently a somewhat similar form, though showing cer- 

 tain notable dift'erences, has been found and studied at Beaufort by Cary 

 (1904I, who reared the larvae until they transformed into the adult form, 

 which, however, he was unable to identify, although he suggests that it 

 may be some species of the genus Amophyllactis. 



Finally Heath (1906) has described a larva of type I which was 

 taken near the Galapagos Islands, and which is specifically distinct from 

 the forms described by Semper and Van Beneden. The fact that I have had 



