62 



HYDROIDA II 



That Nutting (1900 p. 66) should refer this species to Plumularia must be due to his having 

 had small or poorly developed colonies to deal with. From the "Ingolf" St. 55 we have a couple of 

 splendid colonies showing the typical secondary hydrocladia of Polyplumaria in practically every branch, 

 and richly furnished with gonangia. These are situated on the basal part of the hydrocladia -- both 

 primary and secondary, and partly also on the tubes of the stem. 



It might be imagined that the present specimens, with their typical Polyplumaria colonies, 

 were specifically different from Nutting's Plumularia profunda. We found, however, besides the two 



mentioned, extremely luxuriant colonies, also a smaller, single 

 pinnate colony, where only the basal hydrocladia were furnished 

 with secondary hydrocladia, all the remaining hydrocladia being 

 simple. Nevertheless, this colony is likewise fertile, and a fur- 

 ther investigation of the larger colonies shows that here also 

 the secondary hydrocladia are lacking on several branches. In 

 all these colonies, the stem is polysiphonic. But from the "In- 

 golf St 24 we have a quite young, sterile colony, where the 

 whole stem is monosiphonic; only at the bottom of the basal 

 part is a secondary tube developed. Here then, we have the 

 complete transition from Nutting's description to the typical 

 Polyplumaria which the species represents in its fully developed 

 form. The resemblance in detail will furthermore be seen from 

 a comparison of the illustrations here given (fig. XXIX). 



The finding of Polyplumaria profunda in the northern 

 Atlantic is highly interesting. The species is a typical deep sea 

 form, previously known only from West Indian waters. We now 



Fig. XXIX. 



Polyplumaria profunda "Ingolf St. 24. 



a. Hydrocladial internodium. *. Internodium find, that it penetrates in deep water right up into Davis Strait 

 of the primary stem tube, with apophyse. (X6o). -* ,1 T i J 



and Danmark Strait, and to the southern slope of the Iceland 



region, where the warm and salt Atlantic water predominates. It is evidently not able to pass over 

 the submarine ridges or into strictly boreal waters. 



Nemertesia L,amouroux. 



Upright colonies with as a rule pronounced main stem, which may be branched or uu- 

 branched, generally articulated and furnished with strong apophyses bearing finely built hydro- 

 cladia. The hydrocladia are single, unbranched. The colonies are furnished with stalked, two-chamb- 

 ered and mobile sarcothecse, and have in addition, on each apophyse at its upper side where it pro- 

 ceeds from the stem, a large sessile sarcotheca ("mamelon"). The hydrocladia are segmented, and have 

 several hydrothecse, which as a rule are fused throughout their entire length with the branch. The 

 hydrocladia are generally situated in several rows in fully developed colonies. 



Formerly, in drawing the limits for this genus, the principal stress was laid on the fact that 

 the hydrocladia are in multiserial arrangement, not merely in two rows as in Plumularia. This cannot 



