408 
Mr Menem , 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 Zoanthella, 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 
Zoanthella. 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 transvex’se muscles on the 
mesenteries or in the body wall, 
