408 Mr Menon, Notes on Semper 's Larvae. 



part in the locomotion of the animal. The animal has a gray 

 colour, with dark brown patches, especially at the aboral end. 



After going through the sections, I have little to add to Van 

 Beneden's most excellent description. The stomodaeum is short 

 and its walls are thrown into folds. Except near the lower end 

 of the stomodaeum there is no correspondence between the ridges 

 and grooves and the chambers and mesenteries. Though Van 

 Beneden believes in the existence of a ventral siphonoglyph I 

 have not been able to find any indication of it. There is no 

 difference in length between the dorsal and ventral regions of the 

 stomodaeum. It is only a comparison of the arrangement of the 

 mesenteries of this form with that of other Zoantheae that justifies 

 the use of the terms dorsal and ventral. 



There are twelve mesenteries, six large and complete, and six 

 small and incomplete. The three pairs of macromesenteries differ 

 considerably in size : their arrangement is the same as that de- 

 scribed by Van Beneden. The differences between the micromes- 

 enteries are not quite so marked. The dorso-lateral pair seem to be 

 the largest ; of the two remaining pairs, the dorsal pair are slightly 

 smaller than the ventro-lateral. This is different from the account 

 given by Van Beneden, according to whom the dorso-lateral are 

 the largest and the ventro-lateral the smallest, the dorsal pair 

 being thus intermediate in size. The order given above, though 

 differing from Van Beneden's, agrees with what obtains in Semper's 

 second larva. A diagram of the arrangement of the mesen- 

 teries of Zoanihella, with the differences between the micromesen- 

 teries slightly exaggerated, is given in fig. 3. The probable order 

 of their development is also indicated in the same diagram. It 

 has been objected to thus deducing, from the size of the mesen- 

 teries, their order of development that the incomplete mesenteries 

 are not necessarily later formations than the complete ones, but 

 that their incompleteness may be due to other causes, McMur- 

 rich (2). This objection certainly does not hold good in the case 

 of Zoanthina, and most probably does not do so in the case of 

 Zoanihella. It seems to be perfectly reasonable to infer the order 

 of the mesenteries in these forms from their size until actual facts 

 are brought forward to disprove it. 



The longitudinal muscles of the mesenteries, as far as they can 

 be made out, are arranged in the manner described by Van 

 Beneden. The dorsal pair of micromesenteries and the ventral pair 

 of macromesenteries have their longitudinal muscles on the faces 

 turned away from the dorsal and ventral median chambers respec- 

 tively. The remaining macromesenteries have their muscles on 

 their ventral faces, and the micromesenteries on their dorsal faces. 

 I have not been able to detect any transverse muscles on the 

 mesenteries or in the body wall, 



