THE HYDROIDS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 9^ 



taneously. While in Nutting's specimens all the leaves had made their appearance before 

 even the primary pair had reached full development, here, when only five pairs are 

 recognisable, the two first-formed pairs are already full grown ; and when six pairs are 

 visible the earliest three have reached full development, the later ones being in a state 

 of decreasing perfection. 



While some of the corbulse are wholly closed some remain partially open, their 

 leaves, at least towards the tip, bearing nematophores on each side, and remaining 

 separate from each other. In the latter case the gonophores are always male, in 

 the foi-mer no gonophores remained ; but since maleness and openness go together, 

 as they do in so many other cases, it seems probable that in this species we have 

 an example of sexual dimorphism of the type described by Mr H. B. Torrey and 

 Miss Martin (1906). 



The depth of a hydrotheca varies from 0'27 to 0"28 mm., its diameter at the mouth 

 from 0'17 to 0"19 mm. ; measurements agreeing with those of Jaderholm. 



Locality. — On sponges and algse from the entrance to Saldanha Bay, Cape Colony. 

 Depth, 25 fathoms. Bottom deposit, sand and kelp. 21st May 1904. 



Aglaophenia minima, Nutting, 1900. 



Two colonies (the larger 1 cm. high) are distinguished by their cylindrical, keelless 

 hydrothecse with short projecting mesial nematophores as belonging to this species. In 

 addition to the septal ridge, mentioned by Nutting, which traverses the hydrotheca- 

 bearing internode at the level of the intrathecal ridge, another is evident opposite the 

 base of the supracalycine nematophores. The opening of the hydrotheca is bordered 

 by nine, instead of by eight teeth ; and in the mesial nematophore of some of the hydro- 

 thecse a slight chitiuous constriction, almost in line with the profile of the hydrotheca,, 

 is apparent. The nematophores on the stem internodes are arranged as follows : — A 

 solitary long nematophore on the front and at the proximal end of the internode ; and in 

 the angle between the hydroclade process and the stem, a double nematophore, with two 

 diverging processes each bearing a terminal aperture. Only a single opening, however, 

 connects the cavity of the double nematophore with that of the colony. The hydroclade 

 process itself bears a large simple nematophore on its anterior surface, and to this appears 

 to be due the bifurcated appearance mentioned by Nutting. 



No gonangia were present. 



Measurements : — 



Stem internodes, length 



0-45-0-56 mm 



,, diameter 



0-08-0-10 „ 



Hydroclade internodes, length . 



0-39 mm. 



Hydrotheca, depth 



0-34 „ 



,, diameter at mouth 



0T4 „ 



Locality. — Growing amongst seaweed on the leg of a masked crab. Station 81, 



TRANS. ROY. SOC. EDIN., VOL. XLVII. PART I. (NO. 4). 13 



