CLASS in. TENTACULIFERA. 805 



Under any circumstances the new interpretation of the ingestive phenomena of 

 the Acinetidae, as represented in Sphcerophrya i/tagna, arrived at by Maupas, is of 

 the highest import, inasmuch as it indicates, in a yet more decisive manner, the 

 probable affinity subsisting between this remarkable group and the Rhizopodal and 

 Radiolarian Protozoa. As pointed out by him, indeed, the tentacles of certain members 

 of the last-named group, such as Actinosphccrium, are constructed on a precisely 

 identical form as those of the Acinetan, consisting in like manner of a central shaft 

 or axis of clear transparent sarcode communicating with the central substance of the 

 body, and a more granular cortical layer which is continuous with the peripheral or 

 ectoplasmic layers. Maupas finally cites, in support of the probable Rhizopodal 

 affinities of the .\cinetida3, an instance of a Rhizopod most nearly agreeing with the 

 Lieberkuhnia of Clapari^de and Lachmann, found by him in company with a minute 

 species of Arcdla, and upon which it preyed in a manner coinciding remarkably with 

 that described of Sphcerophrya magna in connection with captured ciliate Infusoria. 

 The extremity of an extended pseudopodium was first thrust into the aperture of the 

 test of the Arcella and a double current set up in its substance, which was not 

 suspended until the entire protoplasmic substance of the Arcella was transferred to 

 its own body-mass in a manner identical with that recorded of SpJucrophrya Magna 

 and Cydidiiirn f^laucoma. 



The possibility of a more or less remote relationship subsisting between the 

 Tentacuhfera and the Hydroid polypes is tentatively discussed at page 104 of the 

 preceding volume ; further thought concentrated in this direction has suggested one 

 or two additional jjoints of correlation. More especially the author has been struck 

 with the similarity of contour, and to no small extent of structure, that subsists 

 between the zooids of the remarkable Tentaculiferous genera Ophryodaidron, 

 Acinetopsis, and Umida, and the so-called " nematophores" of certain Hydroidea, such 

 as Pliniiiilaria setacea, Aglaophcitia pluma, and Ophioda mirabilis, as figured and 

 described by Mr. Hincks in his ' British Hydroid Zoophytes.' Achietcpsis rara and 

 Urniila epistylidis, possessing membranous sheaths or loricse, are more especially 

 suited for comparison in this connection. These nematophores which, in a similar 

 manner as the " Dactylozooids " of the genus MilLpora, would appear to represent a 

 degraded or imperfectly developed form of the nonnal alimentary zooids, take the 

 shape of granular protoplasmic masses enclosed in a cup-shaped cell, and capable of 

 protruding tentaculiform pseudopodic processes nearly resembling the proboscis of 

 Acinetopsis or Op/iiodcndivn, in various directions. It is a remarkable coincidence 

 again that both of these infusorial genera occur as parasites, or rather commensals, 

 of Sertularian zoophytes distinguished for the production of these homoplastic 

 nematophores. A point of relatively minor importance in this connection, but 

 possessing at the same time some slight interest, attaches itself to the fact that, 

 while in no present known Ciliate or Flagellate type is the anterior border of the 

 lorica protected by a series of converging triangular plates or valves forming an 

 operculum such as obtains in Acinda mystadna, a like structural modification is 

 common to the protective loricK or " hydrothecje " of a large number of Hydroid 

 zoophytes such as Catnpanulina repetis and Cuspiddla costata, Hincks. 



The author has found that the representatives of this group are specially suited 

 for permanent preservation, the tentacles remaining extended and retaining all the 

 characters of the living zooids on treatment with osmic acid. The addition of a 

 drop of picrocarmine assists materially in developing the form and position of the 

 endoplast where this structure is not distinctly visible. 



In accordance with the system adopted in this volume, the Tentacuhfera may 

 be divided into two natural subsections or orders as below : — 



Tentacles wholly or partially suctorial Order I. SUCTORIA. 



Tentacles entirely non-suctorial, merely adhesive .. Order II. ACTINARIA. 



And further into groups having family and generic significance in accordance with 

 the accompanying schedule. 



[genera of TENTACULIFERA-SUCTORIA. 



