ATLANT. DEEP-SEA EXPED. 1910. VOL. Ill] 



HYDROIDA. 



its entire length of one foot or even more the same undi- 

 vided branch almost without an exception shows the same 

 number of hydrocladia in a whorl. Thus a branch which 

 is hexastichous at the top is generally so where it branches 

 off, but different branches of the same colony have very 

 often different numbers of hydrocladial series. 



A variable number of internodes is inserted between 

 the hydrocladial base (the "hypophysis") and the first 



Fig. 4. Nemertesia Hartlaubi from Stat. 37. a: hydro- 

 cladial base (X 60); b. female gonangium (X 40). 



hypothecate internode; these inserted internodes are often 

 provided with nematophores, but as often the latter are 

 wanting. Such basal internodes are hardly ever completely 

 missing, and we often find one or two, but seldom three. 

 No general rule, however, could be traced. Between two 

 hydrothecate internodes, one nemetothecate internode may 

 be inserted, or in a few cases two; in still rarer cases 

 this latter may be entirely wanting. 



This species has previously been mentioned only by 

 Ritchie. 1 ) It is closely allied to Nemertesia antennina 

 (Lin.), from which it is distinguished by the arrangement 

 of its hydrocladia and its colours. 



Nemertesia rugosa (Nutting)? 



Near Cape Bojador (Stat. 38) in 77 metres, one small 

 colony, which agrees on the whole quite well with Nut- 

 ting's description. 2 ) The sarcotheca of the hydrocladial 

 base (fig. 5, 5) is more rounded and more strongly built 

 than in most other species, but other differences make 

 the identiiy of the colony uncertain. The hydrocladia are 

 provided with strongly developed internodal septa, but 



Nemertesia ntgo- 

 Hydrocladial base 

 of a colony from Stat. 38. 

 (X 60). 



their division into internodes is 

 far more regular than described 

 by Nutting. The internodes gene- 

 rally have two mesial nemato- 

 phores and in the present spe- 

 cimen they*have only one hydro- 

 theca. Besides this, the length 

 of the cauline processes which 

 form the base of the hydrocladia, 

 varies greatly. 



We are thus compelled to 

 await further details about the 

 American specimens of Nemertesia rugosa, before we 

 can identify the "Michael Sars" specimen with certainty. 



Aglaophenia Lamouroux. 

 Aglaophenia dichotoma (M. Sars) Kirchenpaucr. 



Near Cape Bojador (Stat. 37), a great many sterile 

 colonies from 39 metres. 



These specimens closely agree with those of Aglao- 

 phenia elongata Meneghini, from the Adriatic, 3 ) which, 

 however, were only sparsely branched, whereas the rather 

 slender stems of these colonies branch out luxuriantly and 

 dichotomously. 



Although the present species is probably identical with 

 Aglaophenia elongata, I hesitate in referring it to the latter 



Fig. 6. Aglaophenia dichotoma from Stat. 37. a: Hydrotheca. 



b : portion of the stem showing the arrangement of the 



nematothecae on the internodium. (X 60). 



on account of the absence of gonangia. The hydrothecae 

 (fig. 6, a) and the armature of the stem (fig. 6, b) agree 

 with Aglaophenia elongata, and the Adriatic colonies show 

 the same tendency towards the dichotomous branching 

 so characteristic of the "Michael Sars" specimens. The 



') Hydroids of the Scottish National Antarctic Expedition (Trans. Roy. Soc. Edinburgh, Vol. XLV) 1907, p. 542, pi. Ill, figs 4, 

 4 A and 4 B. 



-) American Hydroids. 1 Plumularidae, p. 70. 

 3 ) Hydroiduntersuchungen III, p. 34. 



