FREE-SWIMMING SPOROSACS OF THE HYDROID GENUS DICORYNE. 283 



For the convenience of systematic workers we have inserted a table summarising 

 the distinctive characters of species of Dicoryne, pp. 280, 281. In this table an 

 endeavour has been made to indicate as far as possible the points in which authors 

 themselves regarded their new species as differing from species previously known. 

 These characters are in some cases highly unsatisfactory. 



Dicoryne conferta and D. flexuosa. — As regards the sporosacs themselves no 

 difference has been observed, but unfortunately the free-swimming stage of 

 D. flexuosa is not known. The "immersion" or otherwise of the blastostyle in the 

 sporosac-cluster seems to us to depend more on the state of contraction of the 

 blastostyle and on the maturity, and therefore size, of the sporosacs, than upon any 

 constant difference in shape. Further, the characters upon which Sars especially 

 relied — the deficiency of wrinkling on the perisarc and the flexile and often dichoto- 

 mously branched stem in D. flexuosa — are characters upon which little weight can 

 be placed, since on occasion they are exhibited by D. conferta. In D. conybearei 

 the number of tentacles has been found to vary from six to sixteen ; a similar range 

 of variation has been observed in D. conferta, and it is possible that twelve is not 

 a fixed number for D. flexuosa. It seems to us that on the whole these two species 

 approach suspiciously close to one another, but since we have not seen specimens 

 attributed to Sars' species we hesitate to state definitely that D. flexuosa is a 

 synonym of D. conferta. 



Dicoryne annulata. — The description of this species given by von Lendenfeld is 

 entirely unsatisfactory. There is no evidence that free sporosacs were seen, and 

 the statement that the generative zooids are " similar to those of the European 

 species" is so vague as to be valueless. Nor is the statement that the "terminal 

 cup-shaped expansions [are] a little larger than in D. conferta " of any significance, 

 for comparison of von Lendenfeld' s figure with North Sea specimens of D. conferta 

 shows that his contrast is inaccurate. The probability is that von Lendenfeld has 

 misinterpreted the structure of D. conferta in this respect from Allman's figure 

 (1871, pi. viii), in which the terminal expansions are scarcely indicated. 



LIST OF WORKS QUOTED. 



Allman, J. G., 1860, "Note on the Structure and Terminology of the Reproductive System in the 



Corynidse and Seitularidye," Ann. Mag. Nat. Hist., (3), vol. vi, pp. 1-5. 

 Allman, J. G., 1861, "Notes on the Hydroid Zoophytes," Ann. Mar/. Nat. H/'tf., (3), vol. viii, 



pp. 168-173. 

 Allman, J.G., 1871-72, "A Monograph of the Gymnoblastic or Tubularian Hydroids," London, Ray 



Society. 

 Bonnevib, K., 1898, "Zur Systematik der Hydroiden," Zeitschr. wiss. Zool., Jahrg. 63, pp. 465-195. 

 Carlgren, O., 1909, "Die Tetraplatien," in Wissens. Ergeb. deutsch. Tiefsee-Expedii. " Valdivia," 1898- 



1899, Jena, vol. xix, pt. 3. 

 Chun, C, 1896, "Ccelenterata," in Bronn's Klassen u. Ord. des Thier-Reiclis, Bd. ii, Abt. 2. 



