276 ENTEROPNEUSTA FROM THE SOUTH PACIFIC, 



OECOLOGY. 



I found this species in company with Pt. flava in rock-pools, which contained 

 sand between the tide-marks on the weather side of Lifu. I had two specimens, only 

 one of which was available for cutting into sections, the other was overlooked until 

 my arrival home, when it was found to be macerated, but not useless (see PI. XXVII. 

 Fig. 8 a and PI. XXVIII. Fig. Id). 



My former account of Sp. porosa (loc. cit.) was illustrated by a sketch drawn 

 from the living animal which showed the dermal pits in the genital region in dorsal 

 view. These pits introduce us to a new category of structures in the Enteropneusta. 



Besides the truncal canals of Spengelia there is another ancient structure which 

 occurs in the Spengelidae and nowhere else among the Enteropneusta. I refer to the 

 vermiform process of the stomochord. Apart from what is stated near the end of this 

 memoir I shall not attempt to offer an explanation of this organ, although I believe 

 one is possible. Suffice it to say that, for my part, I am convinced that the vermiform 

 process is to be regarded as an integral constituent of the stomochordal complex, but 

 that it has only been retained by the members of this family. As I have just 

 intimated, I think it is possible to arrive at the probable approximate explanation of 

 the vermiform process, but it would be difficult, at present, to make it convincing. 



