X, D. 2 Light: Philippine Alcyonaria 165 



owing to the lack of fixed characters and the instability of such 

 diagnostic characters as are used; for example, the number of 

 rows of pinnules, as their shape and their relative size and posi- 

 tions differ to a great extent with the state of contraction of the 

 colony when killed. The same difficulty is encountered in the 

 genus Anthelia. Systematic work on the species of these genera 

 should deal first with the living animals and then with the 

 preserved specimens. 



One colony of Xenia is of interest in that it consists of many 

 small branched or single stalks bearing unusually small polyps. 

 These stalks, which are scattered over the branches of a dead 

 colony of Seriatopora, are connected by slender creeping stolons. 

 A number of other specimens are very similar to Xenia hicksoni 

 Ashworth,^! and one resembles Xenia rigida May," but shows 

 no dimorphism. 



The collection contains specimens of Heteroxenia elisebethse 

 Kolliker ^^ from two localities which show the marked dimor- 

 phism maintained by Kolliker,^'^ Bourne,^'* Ashworth,^^ and others, 

 but denied by May.^*- Schenk,^^^ Haacke,^" Kiikenthal,^" and others. 

 The number of siphonozooids is so great in proportion to the 

 number of autozooids, their size is so uniform and so much less 

 than that of the autozooids, and these conditions have been noted 

 by so many independent workers for specimens from so many 

 widely separated habitats that it seems hardly conceivable that 

 we have here merely growing polyps. If they are only auto- 

 zooids in different stages of development why should so many 

 young polyps of the same age be found on the same colony and 

 why should observers in so many different parts of the world 

 and at different seasons of the year find them at the same stage 

 of development as far as the tentacles are concerned and of the 

 same average size? The fact that one can find at the edge of 

 the capitulum series of young autozooids approximating in dif- 

 fering degree the size and form of the mature autozooids tends 

 rather to strengthen the case for dimorphism than to weaken 

 it, for were such developing autozooids never found we would 



"XeniidjE, Willey's Zool. Res. (1900), 4, 68; and Xenia Hicksoni, nov. 

 sp., Quar. Journ. Roy. Micr. Soc. (1891), n. s. 42. 

 '''Jena. Zeitschr. f. Naturw. (1899), 33. 



'' Heteroxenia, Fest. d. Physical. Med. Ges. in Wiirzburg (1874), 13. 

 ''Phil. Trans. (1895). 



"Abhandl. d. Senckenb. naturf. Ges. (1896), 23, pt. 1. 

 "Zool. Garten (1886). 

 " Versuch einer Revision, etc. 9. Xeniiden. Zool. Jahrb., Sj/si. (1901), 17. 



