282 ERNEST WAEPvEN. 



of the liydranth is internally constricted by a larg-e mass of 

 cellular skeletal endoderm {h.M.), which constitutes the basal 

 support of the proximal tentacles {'p.t.). These are provided 

 with cellular skeletal endoderm in place of the more usual 

 septate structure, and it is continuous with the basal mass. 

 Over the skeletal endoderm there is an epithelium (e.ep.) of 

 ordinary endoderm with numerous vacuolated cells {u.c). 



The cavity of the basal dilatation (h.d.) is lined by elongated 

 endoderm cells with large granules. This chamber is partially 

 separated off from the rest of the digestive cavity of the 

 hydranth by the projecting skeletal endoderm {h.M.), and the 

 communication which is left tends to be more or less bridged 

 across by a thin sheet of cells {s.e.) continuous with the endo- 

 dermal epithelium. 



Systematic Position. — The present species is characterised 

 by the presence of the large dilatation at the base of the 

 hydranth. In general aspect and in the erect position of the 

 peduncles it resembles Tubularia attenuata AUnuoi^ and 

 Tubularia humilis Allman^ from the British and Irish 

 coasts. 



In a number of species of Tubularia the hydranth is 

 supported on an annular expansion of the hydrocaulus. The 

 dilatation at the base of the hydranth of betheris would 

 naturally be directly compared with this annular expansion ; 

 but in betheris, at any rate, there is a distinct differentiation 

 of the endoderm lining it (fig. 12), and doubtless it accom- 

 plishes some special physiological function. Without a 

 detailed knowledge of the mode of development of the 

 hydranth it is not possible to decide whether it should be 

 regarded as a basal differentiated portion of the hydranth, or 

 as an expansion of the upper end of the hydrocaulus. 



(7) Pennaria australis Jktle, var. cooperi Warren. 



Pennaria australis Bale, 'Cat. of the AuBtralian Hydroid Zoophytes.' 



1884 p. 45. 



In the ' Ann. Nat. Gov. Mus.,' vol. i, p. 73, the author 

 ' AUmau, G. T., op. cit.. pp. 410-411. 



