[fraser] HYDROIDS OF THÉ VANCOUVER ISLAND REGION 1M 



Genus CORYDENDRIUM 



Trophosomc. — Stems fascicled and branched, hydrant hs with 

 scattered filiform tentacles. 



Gonosome. — Gonophores borne on stems or branches in the form 

 of fixed sporosacs. 



For some time this genus was known only by the species para- 

 siticum described by Linnaeus as Sertularia parasitica? and placed 

 in the genus Corydendrium by van Beneden 3 . Allman, getting the 

 impression from Cavolini's description that the species produced 

 free medusae, placed it in the family Turridœ 4 . Later Weismann showed 

 that the species did not produce free medusae. 5 



When Nutting worked out the hydroids obtained during the 

 Hawaiian expedition he found two new species both of which he 

 called Corydendrium. 6 In the one case, C. corrugatum, he found no 

 gonosome, but in the other C. minor, he found medusa-buds. The 

 presence of free medusae made it impossible to include this species 

 in the family Clavidœ as defined by Allman but the difficulty was sur- 

 mounted by including in the family Clavidœ forms that produced free 

 medusae as well as those that produced fixed sporosacs, both repre- 

 sented in the genus Corydendrium . 



Later Thornely, without any reference to Nutting's paper, 

 described a species from the Gulf of Manaar, using the name Cory- 

 dendrium chevalense. 1 



This species had medusa-buds and hence corresponded to Nutt- 

 ing's species C. minor, but it was placed in the family Turridœ and not 

 in the family Clavidœ. 



It appears unusual to include in one genus forms that produce 

 free medusa? and those that do not and I do not think it advisable to 

 do so. Since the term Corydendrium was first applied to C. parasiticum 

 which according to Weismann does not produce free medusae, the genus 

 should be retained for such species only that produce fixed sporosacs. 

 The medusa Turritopsis nutricula McCrady is developed from a 

 hydroid with trophosome of similar structure to that of Corydendrium 

 as shown in my Beaufort paper 8 , and as far as I can make out from 

 the descriptions and figures of Nutting and Thornely there is every 



2 Syst. Nat., 1767, p. 1315. 



3 Sur les genres Eleuthérie et Synhydre, 1844. p. 313. 



4 Ray Society, 1871, p. 262. 



5 Die Entstehung der Sexualzellen bei den Hydromedusan, 1888, p. 40. 



6 Hydroids of the Hawaiian Islands, 1905, p. 941. 



7 Pearl oyster fisheries of the Gulf of Manaar, 1904, p. 109. 

 «Hydroids of Beaufort, N. C, 1912, p. 345. 



