GENUS ACINETOPSIS. 855 



adult form, is simply spheroidal, but attached to its fulcrum of support b)' a 

 distinct rigid pedicle. A little later the zooid assumes a pyriform contour, a single 

 terminal proboscis is developed, and the animalcule, as delineated at Fig. 30, most 

 nearly resembles the typical form of O. pediceliatum, represented by Figs. 16 and 17 

 of the same plate. This pedicle may be retained even after the zooid has attained 

 to a considerable size, developed a plurality of proboscidiform organs, and com- 

 menced to propagate by gemmation, as shown at Fig. 28 ; by the time, however, 

 that the full size and complete number of probosces are developed, the pedicle has 

 invariably disappeared, having become either completely surrounded and enclosed 

 within the distended body-mass, or possibly reabsorbed into its substance. The 

 densely granular and opaque character of the parenchyma in this type prevented 

 the clearing up of this point, and neither, owing to the same conditions, was it found 

 possible to detect the presence of either contractile vesicle or endoplast. The 

 vermiform larvte were but sparingly observed in the examples examined ; they 

 corresponded essentially in form and structure with those of Ophryodendron scrtularia:, 

 previously described. 



It will probably be found convenient hereafter to introduce a new generic title 

 for this and any allied species that may be discovered possessing a plurality of 

 proboscidiform appendages. In connection with this distinctive feature, it might, 

 perhaps, be maintained that Ophryodendron midticapitatum potentially represents a 

 polyzoidal colony-stock after the manner of Dcndrosoma ; on the other hand, a 

 near comparison with reference to these appendages might be instituted with 

 DendrocoincUs paradoxus, '\\\\islTA\.eA immediately above it in PI. XLVIIIa., assuming 

 necessarily in this case that each proboscis of the Opiuyodcndron is, as in the branch- 

 like extensions of Dendrocomctes, the homologue of the number of tentaculate organs 

 normally developed by the simpler Acinetidag. 



Genus II. ACINETOPSIS, Robin. 



Animalcules ovate, excreting and inhabiting a stalked, membranous, 

 transparent lorica, bearing a single, anteriorly developed, contractile, 

 proboscidiform tentacular appendage, the distal extremity of which is not, 

 as in Ophryodendron, beset with supplementary cirri. Inhabiting salt 

 water. 



Acinetopsis rara, Robin. Pl. XLVIII. Figs. 43-45. 



Lorica wineglass-shaped, transparent, about one and a half times as 

 long as broad, mounted on a very slender, straight or flexuose pedicle that 

 equals or slightly exceeds the lorica in length ; body almost completely 

 filling the cavity of the lorica, its substance uniformly granular ; probosci- 

 diform tentacle very attenuate or filiform when extended, its length then 

 equalling five or six times that of the body, exhibiting throughout 

 when contracted an exteriorly developed, very delicate, plicate, spiral 

 fibrilla ; contractile vesicle single, subspherical ; endoplast unobserved. 

 Length of lorica 1-300". 



H.\B. — Salt water, on various Sertularian zoophytes : Concarneau 

 (Ch. Robin). 



This very remarkable form is figured and described by Prof Ch. Robin in the 

 'Journal de I'Anatomie et de la Physiologie,' tom. xv. 1879,* and is of more than 



* See also tranblation in 'Journal of the Royal Microscopical Society,' Oct. 18S0. 



