THE HYDROIDS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 91 



deviations from the normal structure of the athecate internodes have been observed 

 where, instead of one, two nematophores were present. 



Gonosome. — The gonangia arise laterally from the hydroclades. They are situated 

 immediately beneath the hydrothecae on a short process from the hydroclade internode, 

 between which and the body of the gonangium a short internode intervenes. In size 

 a gonangium is three or four times as large as a hydrotheca ; in shape it is broadly 

 ovate, tapering proximally into a short stalk which rests upon the intervening internode 

 mentioned above, and abruptly truncated distally, where the large terminal aperture is 

 closed, prior to the maturity of the contents, by a one-flapped operculum attached by 

 its abcauline edge to the wall of the gonangium. Two large nematophores are present, 

 one on each side of the gonangium near its base. 



Measurements : — 



0-28-0-32 mm. 



nuucw,re mucmuura, icngun 



Thecate ,, „ * . 



0-36-0-38 



Hydrotheca, length 



0-20-0-24 



„ breadth at mouth . 



0-21-0-24 



Gonangium, length 



0-88-0-91 



,, greatest breadth . 



0-53-0-57 



Locality. — As previously recorded — entrance to Saldanha Bay, Cape Colony. 25 

 fathoms. 21st May 1904. 



Growing on a sponge from the same locality were several simple colonies up to 

 7 mm. high. Although there are no signs of fasciculation, nor even of true branching, 

 the minute structure corresponds so exactly with that of A. scotice that I cannot but 

 conclude that the small colonies represent an early stage of that species. They bear no 

 gonangia. 



MonostcBchas quadridens (M'Crady, 1859). 



Two minute colonies of this species were found growing on the leg of a masked 

 crab. They differ from the typical form described by Nutting (1900, p. 75) only in 

 their minuteness — they are less than 1 cm. high — and in the length of the athecate 

 intermediate internodes of their hydroclades. Although each bears two or three hydro- 

 clades, neither of the colonies is branched ; yet circular holes at the bases of some of the 

 hydrothecae, indicating the point where a gonangium had been attached, show that the 

 colonies are mature. The unusual position in which the colonies were growing is 

 probably responsible for their smallness, for an unstable foundation is frequently 

 accompanied by a dwarfed fauna. 



Measurements : — 



Stem, diameter 

 Thecate internodes, length 

 Intermediate internodes, length 

 Hydrotheca, depth 



,, diameter at opening 



0*14 mm. 

 0-42-0-46 mm. 

 0-56-0-73 „ 

 0-15-0-17 „ 

 0-20-0-22 „ 



Length measured from straight node to furthest point of oblique node. 



