6 4 



HYDROIDA II 



have monosiphonic stem; not until later does it become canaliculate, and finally, in fully developed 

 colonies, we find purely polysiphonic basal parts of the stem, where secondary tubes cover the canali- 

 culate central tube. Thus the limits between Nemertesia and Antcnnopsis become effaced, and these 

 genera must in consequence, as I have previously maintained (1912 p. 28), and as Stechow also points 

 out (1913 p. 25) be united into one. Similarly it follows, that Stechow is correct in placing Sibogella 

 under Nemertesia. 



Bedot, in a work which has just appeared (1917) treats of the genus Nemertesia at length, 

 unfortunately, however, without giving any synopsis of the generic characters. It is nevertheless clear 

 that Bedot inclines to regard the canaliculate ("pluricanaliculee") stem as a family trait. The char- 

 acter is developed, as mentioned above, only in somewhat 

 larger colonies generally at least 5 cm high - - it is 

 moreover often lacking in large distal parts of the 

 colony in the northern species, where the stem fre- 

 quently retains its primary ("unicanaliculee") character. 

 And finally, the primary "pluricanaliculee" stem tube 

 is secondarily covered, as in Nemertesia ramosa, by 

 tubes "unicanaliculees" to a greater or lesser extent. 

 This in itself detracts from the value of the character 

 in question. But in addition, it is also found to stand 

 in a certain relation to the dimensions of the stem 

 tube; thick, single stems are "pluricanaliculees" in spe- 

 cies within the same genus, where the thin ones are 

 constantly "unicanaliculees" (cf. for instance Tubularia}. 

 As a matter of fact, the two types "fasciculee" (poly- 

 siphonic) and "pluricanaliculee" (canaliculate) represent 

 parallel processes of development towards the same 

 end. And as we are unable to take the former 

 as basis for generic distinction, so also the latter 

 character must be considered quite inadequate as a 

 means of distinguishing between genera (or families). 



t 



Fig. XXX a c. Nemertesia antenmna, juv. "Ingolf" St. 98. 

 a. The entire colony (nat. size). *. Internodium of the 

 hydrocaulus with the hydrocladial apophyse, showing the 

 sessile sarcotheca. c. Two successive internodes of a 

 hydrocladium (* and c X 80). 



Nemertesia antennina (Linne) Lamouroux. 

 1758 Sertularia antennina, Linne, Systema naturse, ed. 10, p. 8ti. 

 1812 Nemertesia antennina, Lamouroux, Extrait d'un memoire sur la classification des polypes coralli- 



genes, p. 184. 



Colonies with unbranched or quite exceptionally slightly branched canaliculate and segmented 

 stems. The apophyses are set in circles on the internodium, each circle containing three to six or 

 even more apophyses; the internodia are revolved, so that the stem has twice the number of longitu- 

 dinal rows of apophyses. Near its point of origin, the apophyse has on its upper side a comparatively 

 small, sessile sarcotheca ("mamelon") and two or three irregularly arranged, stalked and two-chambered 



