FORSKALIIDAE. 269 



tioii of the siphosome, far advanced in Athorybia, and complete in Anthophysa, 

 together with the absence of a secondary porus in the pneumatophore of Athory- 

 bia, contrasted with its presence in Physophora, show that though both these 

 latter genera have the stem reduced in length, they are not members of a single 

 developmental series. Now, although the complexitj^ of the pneumatophore 

 of Athorybia is good evidence that the genus is not ancestral (Chun, '97), the 

 resemblance between it and the "Athorybia" larva is too close to be accidental. 

 The most plausible explanation is one partially advanced by Schneider ('98, 

 p. 159), namely that Athorybia represents the "Athorybia" larva become sexu- 

 ally mature without undergoing the usual metamorphosis but with the pneu- 

 matophore highly specialized. In other words, it is an instance of development 

 arrested in some lines, accelerated along others. Derived from the parent 

 Agalmid stock are four groups with shortened axis. These are: 1, Nectaliinae, 

 with axial pneumatochone, with both nectophores and bracts, and siphosome 

 alone reduced; 2, Physophoridae, with highly specialized ventral pneumato- 

 chone, with nectophores and no bracts, and much reduced siphosome; 3, 

 Anthophysidae, with highly specialized bracts, rudimentary nectophores if any; 

 no specialized pneumatochone; 4, Rhodaliidae, with highly specialized dorsal 

 pneumatochone, with nectophores, but no bracts. 



The probable position of Anthophysidae has just been noted. Physo- 

 phoridae and Rhodaliidae could both be derived from Nectalia. But it is impos- 

 sible to connect the two in direct genetic series with each other or with the 

 Anthophysidae. The position of the pneumatochone is an unsurpassable ob- 

 stacle to regarding Physophora as the parent of the more highly specialized 

 Rhodaliidae, while the absence of nectophores and presence of bracts, and the 

 regressive development of the pneumatochone in Anthophysidae, forbids the 

 association of that group with either. They represent diverging lines of evolu- 

 tion. 



Forskaliidae Haeckel, 1888. 



Haeckel ('88b) recognized four genera in this family: viz Strobalia, Fors- 

 kalia, Forskaliopsis , and Bathyphysa. But as Bedot ('93a) has pointed out in 

 his revision of this family, the only species of Forskaliopsis, F. rnagnifica Haeckel, 

 was never described; it was probably a Forskalia. Strobalia is equally vague, 

 only the generic characters having been given by Haeckel, and it is at least 

 problematic whether any existing species corresponds to his account. Finally 

 it has been shown that Bathyphysa belongs to a different suborder, the Rhizo- 



