177 HYDROIDA. BALK. 



deformed and distorted, and partly overgrown by perisarcal 

 tubes such as form the fasciculate structure of the hydrocaulus. 

 The hydrothecse of the corbula are extremely rudimentary 

 structures. They are borne on the distal edges of the leaflets, 

 just above their origin ; there is first a projecting sai-cotheca, 

 above it the hydrotheca, and one or two smaller sarcotheca? 

 higher up. The hydrotheca itself is very irregular in form, and 

 very small ; it often has a distinct single lobe on the outer 

 margin, but the inner side seems to be adherent to the leaflet. 

 It has no lateral sarcothecae. The hydrotheca, with the inferior 

 sarcotheca, forms a very slight projection corresponding to the 

 more prominent lateral spur which in some species bears a 

 hydrotheca, and in others sarcotheca? only, and it similarly 

 covers an opening between the bases of the leaflets, which, how- 

 ever, is here very small, and which I have only been able to dis- 

 tinguish in the male corbula. The structure is very difficult to 

 make out, and it is only after considerable hesitation, and still 

 with some doubt, that I have come to the conclusion that these 

 small indefinite receptacles are really hydrothecse. 



The characteristic foliaceous appendages of the corbula are of 

 the same class as those which occur in A. tasmanica and allied 

 forms, but they are here even more developed, standing out from 

 the sides of the corbula as much as above it, and surrounding it 

 with a complete eheval-de-frise except immediately behind the 

 rachis. There are two main lobes rising from the edge of each 

 leaflet, the lower and smaller one curling back towards the 

 rachis, while the larger spreads laterally and above the corbula,, 

 dividing into three or four large angular secondary lobes of 

 thick perisarc, with all the margins bordered with sarcothecae. 

 The diameter of a female corbula seen from above, and measured 

 across these appendages, will average at least three times the 

 diameter of the closed receptacle alone. Female corbula? may 

 average about 8 or 9 mm. in length, male about 5 or (5 mm. 



The species seems rather prone to irregularity of growth. 

 I have seen two or three instances of isolated secondary 

 hydrocladia, each of which grew out of a hydrotheca, and stood 

 out at right angles to the primary hydrocladium. In another 

 case a rarnule commenced as an ordinary hydrocladium, the first 

 five internodes bearing hydrotheca?, it then assumed the character 

 of a branch, producing first an ordinary hydrocladium, then a 

 gonocladium with a corbula, on the same side, then several short 

 alternate hydrocladia, after which it passed uninterruptedly into 

 a corbula. 



LOG. Thirteen miles north east of North Reef, 70-74 

 fathoms ; thirty-eight miles north east of North Reef Light- 

 house, Capricorn Group, off Port Curtis, Queensland, 74 

 fathoms. 



