412 Mr Menon, Notes on Semper s Larvae. 



As in Zoanthella there is a uniform covering of small cilia ; 

 but what characterises this form is a ring of especially long cilia 

 attached to the bottom of a groove running round the body at about 

 a third of its length from the oral end. This circular band is not 

 so markedly iridescent as the longitudinal band of Zoanthella. The 

 cilia are directly orally and work together rhythmically as if they 

 formed a rhythmically vibrating membrane (the movement can be 

 best compared to that of the umbrella of a jelly-fish). The ciliated 

 band pulsates very rapidly for a few seconds, then stops for a short 

 interval, and then pulsates again. The result of this movement 

 of the cilia is that the larva darts .through the water, aboral end 

 directed forwards, for a few millimeters, then rests on the bottom 

 of the vessel, and then darts through the water again — its orbit 

 thus consisting of a number of small arcs. These movements 

 were best observed in the youngest specimen, which was remark- 

 ably active. The older specimens, when not lying on the bottom 

 of the vessel, suspend themselves in the water, the circular band 

 of cilia moving very slowly and only occasionally. The movement 

 of this ciliated band thus differs from that of the ciliated bands of 

 an ordinary trochosphere. 



The mouth is a quadrangular opening. I have not found the 

 oral papillae mentioned by McMurrich. The wall of the stomo- 

 daeum is thrown into longitudinal folds and grooves which cor- 

 respond to the mesenteric chambers and mesenteries. They be- 

 come less marked towards the mouth. There are five ridges 

 projecting into the lumen of the stomodaeum and corresponding 

 to the dorsal and the two pairs of lateral primary mesenteric 

 chambers ; there are four grooves opposite the attachments of the 

 dorsal and lateral pairs of mesenteries to the stomodaeum. The 

 ventral region is occupied by one large groove, the siphonoglyph. 

 These structures can be made out in the living larva as well as in 

 sections, and are thus quite natural. 



The inner organisation agrees in all essential respects with 

 that of Zoanthella. A siphonoglyph can be distinctly made out 

 in larger specimens. It lies, as is usually the case in the Zoan- 

 theae, on the side of the stomodaeum, which is on that account 

 designated ventral. In earlier stages the siphonoglyph appears to 

 be wanting, its lower end is not produced into a lappet. 



There are twelve mesenteries, six large and six small, having 

 the same arrangement as in Zoanthella. The ectoderm has, in 

 addition to ordinary cells, gland cells, some of which have coarse 

 granules and others clear, non-staining, reticulate contents. Pig- 

 ment cells with brown or yellow granules are present, but are not 

 so numerous as in Zoanthella. There are two kinds of nematocysts 

 (fig. 9), the larger of which are much more elongated relatively 

 than the larger nematocysts of Zoanthella. These occur in large 



