276 MB. J. E. DUEEDEN ON 



tentacles gives a strongly bilateral character to the larva, ex- 

 ceeding that ever exhibited by Lehrunia. The latter seems more 

 closely to resemble Bunodes verrucosa {B. gemmacea), in which 

 Lacaze-Duthiers found the octoradiate stage to be of longer 

 duration. 



The succeeding stages, showing the manner in which from 

 tentacles of heterogeneous origin the hexameral cycles of the 

 adult are obtained, do not now concern us, except to say that in 

 all probability Lebrunia passes through similar phases. 



Aulactinia larvae afford somewhat similar results. I obtained 

 freshly -extruded examples with only six tentacles developed, one 

 smaller and one larger tentacle on each side of the dorso-ventral 

 tentacles. Others, again, show eight tentacles ; of the new pair 

 one arises on each side of the dorsal tentacle. 



Among the Cerianthidse McMurrich (1891 a) and E. van 

 Beneden (1891), in the same year, have confirmed the previous 

 observations of Agassiz and Kowalewsky, that the first six 

 tentacles arise in lateral pairs, and that then a single median 

 tentacle — the sulcar — appears. No radial phase is ever assumed 

 in any of these earliest stages yet described. Prof. G. von Koch 

 (1897, p. 759), however, in the numerous larvae of Garyophyllia 

 cyathus which he had under observation, found the first twelve 

 tentacles to appear apparently at one and the same time, six 

 larger alternating with six smaller, just as in the adult. In one 

 case they developed in pairs, the dorso-ventral pair appearing 

 first. 



The relation of the difierent tentacles to the internal mesen- 

 terial spaces is described later (p. 297). 



III. Internal Anatomy and Histology. 



In all about thirty extruded larvae were obtained, and reared 

 to different stages within the course of a week. Among a 

 number of adults collected in 1896, at the Port Royal Cays, a 

 polyp with its interior crowded with preserved larvae was also 

 detected. Cutting this across upwards of thirty examples 

 floated out freely, or were easily separated from among the 

 tissues. These were devoid of tentacles, and internally all pre- 

 sented precisely the same stage of development — a stage, it will 

 be seen later, slightly in advance of that exhibited by the 

 youngest of the expelled larvae. In speaking, therefore, of early 



