244 EXTEROPNEUSTA FROM THE SOUTH PACIFIC, 



OECOLOGY. 



Pt. flava occurs in clean loose coral-sand between the tide-marks. It does not 

 burrow to any great extent but frequents the superficial layer of sand, and the meshes 

 formed by the roots of seaweeds and crevices in stones. I have found it in three 

 localities, viz. at the Isle du Phare opposite Noumea, at the Isle of Pines, and at Lifu. 

 Hill has recorded it from Funafuti and Mr J. Stanley Gardiner brought back a few 

 specimens from the same locality. It is a gregarious species and is usually to be 

 obtained in considerable numbers. As a rule, Pt. flava seems to prefer the weather 

 side of the islands, that is to say the side which is exposed to the prevailing wind. 

 This preference is clearly shown at Lifu, the lee side of which forms a large inlet 

 known as Sandal Bay. I never found Pt. flava on the shores of Sandal Bay, but had 

 to cross over to the opposite side of the island, which is bounded by a continuous 

 fringing reef, to obtain my material. 



In a small percentage of specimens there is found a parasitic Copepod which lives 

 in the genital pleurae causing a prominent tumour or gall. I gave a figure of an 

 infected specimen in my former paper on this species (loc. cit). A similar parasite was 

 found by Spengel in Pt. minuta and named Ive balanoglossi Paul Mayer. In Pt. 

 australiensis Hill found that a similar parasite infested a large proportion of the 

 individuals of the species. 



The intimate association of quite distinct species of Enteropneusta is an interesting 

 feature in their distribution. At Funafuti Pt. flava and Pt. hedleyi were taken together 

 by Mr Charles Hedley. At Lifu I took Spengelia purosa in company with Pt. flava 

 and in New Britain Pt. ruficdlis n. sp. inhabits the same burrows with Pt. carnosa n. sp. 

 Pt. flava does not practise autotomy in the same way as this takes place in Pt. 

 carnosa and Sp. alba (cf. PI. XXVII. Figs. 6 and 9) but it is fragile and excessively 

 prone to laceration. The wall of the hind-gut is well vascularised and the anal orifice 

 may be seen to open and close periodically irrespective of defaecation, thus suggesting 

 anal respiration. 



