HALISTEMMA. 129 



Fam. STEPHANOMIADiE. 



Genus HALISTEMMA {miJii). 



Tentacular sacculi, without involucra, and ending in a single filament. The nectocalyces 

 in a double parallel series. 



HALISTEMMA RUBRUM. PI. XH, fig. 9. 



Agnlma rubra, Vogt. 

 Agalmopsis punctata, KoUiker. 

 Agalma {Agalmopsis) rubrum, Leuckart. 



This species was discovered by Vogt, and was subsequently described by KoUiker, 

 whose figure (the distal end of ti)e hydrosoma being omitted for want of room) I have copied. 

 As Leuckart (' Z. N. K.,' p. 73), however, has, with the works of Vogt and KoUiker before 

 him, studied this species, I prefer to give an abstract of his description of it. Professor 

 Leuckart considers this form (tiie type of his Agalmopsis) to belong to a sub-genus of At/alma, 

 so that the general characterisation of this genus, which he gives at page 72, is applicable to 

 Halisiemina. 



The pneumatophore is of moderate size, and is without a pigment spot. The 

 nectocalyces, of which there are sometimes as many as thirty pairs, are cubical, compressed 

 from above downwards, and provided at their proximal ends with two pairs of processes, an 

 upper and a lower, the latter having a very considerable size and a wedge-like form, and 

 projecting much more than the upper ones. These processes serve to embrace the ccenosarc, 

 and to interlock with the opposite nectocalyces. Cf the nectocalycine canals, there are not only 

 the ordinary four radiating and the circular, but in addition curved caecal processes (mantelge- 

 fasse), as in Ilippopodius and Proi/a. The lateral radial canals form a double loop. The 

 cncnosarc is spirally coiled. The polypites are exceedingly large, and the hepatic ridges have 

 a reddish colour. 



The branches of the tentacles are very large, having a length of as much as a line in the 

 coiled condition, and of four lines when extended. 



Tlie hydrocysts are slender, and without projecting villous ridges, but otherwise 



resemble young and undeveloped polypites. Their tentacles are slender, and without 



sacculi. Four to eight hydrocysts in various stages of development are interposed between 



every pair of polypites. 



17 



