BAMFORD— PELAGIC ACTINIARIAN LARV^ 403 



sides of the lateral mesenteries, becoming detached at its ends so as to form free filaments 

 within the chambers. Such a free filament has passed through the left dorso-lateral 

 mesentery. Parieto-basilar muscles are developed. 



The ectoderm of the column contains granular glands and nematocysts with close 

 spiral threads. That of the aboral part is very thick and has numerous nematocysts with 

 loose irregularly coiled threads, the close spiral kind being absent. The ectoderm of the 

 stomod^um is ciliated with numerous granular glands, the filaments are similar with large 

 and long nematocysts with close spiral threads, and others which stain deeply but not 

 clearly ; there are thus three (or foin-) kinds of nematocysts. The endoderm has no 

 nematocysts ; zooxanthellae are present in its cells and there are numerous vacuoles which 

 appear to have been occupied by them. Between the mesenteries parietal endodermal 

 outgrowths, which are large aborally, project into the coelenteron. 



Loc. South of Saya de Malha Bank, surface. 



9. Larva II. (PL 24, figs. 17—19.) 



The larva is white, cylindrical, tapering slightly aborally with a depression but 

 no pore ; it is 1 "5 mm. long and 1 mm. broad. The peristome shows eight grooves, 

 which continue down the side of the column. The stomodseum is rather more than 

 a third the length of the column and has a circular lip about its middle projecting mto 

 its cavity. 



The eight mesenteries are complete with filaments on all and reach to the aboral end, 

 but their muscles are too little developed for their arrangement to be ascertained. The 

 filaments on the pairs of directives though of considerable length are shorter than those on 

 the lateral mesenteries which almost reach the aboral end ; on the lateral mesenteries they 

 are much convoluted. There is a distinct upturned fold of the enterostomal wall and the 

 connection of the filaments of the lateral mesenteries with this epithelium falls within the 

 mesenterial chambers. 



The ectoderm is only preserved in a few places and its detailed structure is 

 uncertain. That of the stomodseum has granular and mucous gland cells and long 

 narrow nematocysts with a close spiral tln-ead, as well as other deeply stained 

 nematocysts. The endoderm is much vacuolated and the coelenteron is almost filled 

 with loose endodermal tissue. 



Loc. Mauritius, 5 miles west of Black River, 300 fathoms. 



Within the endoderm are three embryos (fig. 20) in different stages of development. 

 Four embryos were described by v. Beneden in the larva of Zoanthina nationalis 

 (v. Beneden). He suggested that the larva and its embryos were offspring of a viviparous 

 parent, and that the embryos found their way into the larva within the parent and 

 subsequently continued their development. In all parts of the endoderm of the present 

 larva, particularly in that of the mesenteries, unicellular cells are found with large 

 nuclei ; these look like reproductive cells. It may also be remarked that with the 

 coelenteron almost filled with endodermal tissue the entrance of young embryos is 

 unlikely. 



