132 McMURRICH. [Vol. V. 



arrangement of the mesenteries of Gojiactinia (SS). Between 

 the dorso-lateral pair of imperfect mesenteries and the dorsal 

 genital mesentery a pair of perfect mesenteries intervened, hav- 

 ing their longitudinal muscles arranged as in the directive mesen- 

 teries, the stomatodaeum showing indications of a siphonoglyphe 

 at the region of their insertion into it. 



It seems probable that the ancestral Anthozoa did not pos- 

 sess a siphonoglyphe. In the simple Alcyonaria {Monoxenia, 

 Hartca, and Haimca) it seems to be absent. In other Alcyo- 

 naria it is, as a rule, present, varying, however, greatly in its 

 development, as has been shown by Hickson ('83), and in all 

 cases is single, marking the ventral surface of the polyp. In 

 the Edwardsiae two siphonoglyphes appear to be the rule, and 

 in these forms, in contradistinction to what occurs in the Alcyo- 

 naria, two pairs of directives are present. It appears as if there 

 was some reason why, when there are two siphonoglyphes, the 

 longitudinal muscles should not be upon the same sides of the 

 mesenteries which are in connection with them ; in other words, 

 it is necessary, for the proper action of the siphonoglyphes, that 

 the longitudinal muscles of the mesenteries in connection with 

 one of them should be upon the dorsal faces, those in connec- 

 tion with the other siphonoglyphe having them upon the ven- 

 tral faces. It is possible that this arrangement has something 

 to do with the preservation of the lumen of the siphonoglyphe 

 when the lips of the stomatodaeum elsewhere are in contact. 



Since the Edwardsias are provided with two siphonoglyphes, 

 that is the condition to be expected in all forms derived from 

 them, and with the majority it seems to be the case. There are, 

 however, numerous exceptions, as in the Sagartids mentioned 

 above, in certain Halcampidae {Pcachia), in the Ceriantheae, and 

 in the Zoantheae. It is evident, however, that the forms of 

 these last three groups have been derived from ancestors with 

 two siphonoglyphes, since they are provided with two pairs of 

 directives. The arrangement of the musculature of the mesen- 

 teries of the Alcyonaria is probably the most primitive one, since 

 it is the most symmetrical. The alternation of the arrangement 

 of the musculature of the ventral directives consequent upon 

 the formation of a second siphonoglyphe came to be so thor- 

 oughly impressed upon the development of more recent forms, 

 that it still persists as a rule when one of the siphonoglyphes 



