8o2 CLASS III. TENTACULIFERA. 



VorticellidEe, such inference being arrived at in connection with the circumstances 

 that many AdnetiB, e. g. Podophrya quaJripartifa, Podophrya can/tesii, and P. phry- 

 ganidarum are found usually closely associated ■nith certain compound Vorticellidag, 

 while in their ciliated embryonic state their resemblance to free VorticdlcB is very 

 remarkable. In accordance, indeed, mth Stein's theory, every one of the earlier 

 known Acinete forms represented but the immature or embrj'onic condition of 

 a Vorticellidan type, the respective species to which they were in his opinion 

 related being indicated in the following specific descriptions.* It was the researches 

 more especially of Messrs. Claparede and Lachmann, having as their end in view 

 the solution of the vexed question of their affinities, that conduced chiefly to the 

 elucidation of the true nature of this remarkable group of organisms, and which won 

 for them that independent position which has since been universally accorded. As a 

 distinct section of the Infusoria, possessing the same status as that of the Ciliata 

 and the Flagellata previously described, and with reference more particularly to their 

 manner of ingesting food, and the character of their tentacle-like appendages, 

 Claparbde and Lachmann conferred upon these Infusoria the title of the Suctoria. 

 More recent investigations having, however, ehcited the existence of forms allied 

 to Acineta in which a portion only of the tentacles are suctorial, or which again may 

 be entirely non-suctorial and simply prehensile. Professor Huxley f has proposed 

 to substitute for the Suctoria the more appropriate title of the Tentaculifera, which 

 is here utilized, Claparfede and Lachmann's name, with the new one of the Actinaria, 

 being at the same time retained for the distinction of respectively the suctorial and 

 non-suctorial series. 



The histological composition of the Tentaculifera corresponds substantially with 

 that of the two classes hitherto described ; an external cuticular layer, internal 

 granular protoplasm, and the essential structures, an endoplast or nucleus and one 

 or more contractile vesicles, are usually recognizable. The endoplast, it may be 

 remarked, is in many forms, e. g. Hemiophrya gemmipara, and Podophrya Stdnii, 

 extensively ramified, though in no instance as yet known is there a multiplicity of 

 endoplastic structures as obtain among many of the Ciliata. The majority of species 

 are sedentary in their habits, thus offering an additional point of resemblance to the 

 Vorticellidoe, with which they were originally correlated. In like manner, while some 

 are sessile, others are stalked, and may be either naked or enclosed within a trans- 

 parent sheath or lorica. Although up to the present time no Tentaculiferous type 

 has been discovered in which the individual zooids are united by their pedicles, and 

 thus form, precisely as in Carchesiiim or Epistylis, a compound zoodendrium, an 

 almost equivalent colonial modification obtains in the genus Dendrosoma. Here, 

 however, the separate zooids, as represented by each tentacuhferous ramuscule, are 

 indissolubly united, possess in addition a common creeping stolon, and more 

 nearly approach the constitution of a multicellular animal or metazoon than can 

 perhaps be predicated of any of the forms previously noticed. A less decisive 

 advance in the same direction is apparently accomplished in the form hereafter 

 described under the title of Ophryodendron multicapitata, while potential multi- 

 cellularity, as with the multinucleate CiUata, would also appear to obtain in all those 

 t)-pes distinguished by the ramif}ing character of their endoplast Although among 

 the majority of loricate species, the protective sheath or lorica differs in no essential 

 respect from those formed by the Cihate or Flagellate groups of the Infusoria, in 

 certain other forms it presents a more complex character. 



Thus in Acineta vorticdloides and A. divisa it has been shown by M. Fraipont % 

 that the fundus of the lorica is separated from the anterior region by a distinct 

 membranous septum or platform, upon which the animalcule's body rests, while in 

 Adncta tubcrosa the membranous wall of the lorica covers in also the anterior 



* Following Stein's lead, a similar subordinate position is accorded to the Acinetidse in 

 Prichard's 'Infusoria,' latest edition, iS6l. 



t ' Anatomy of the Invertebrata, ' 1877. 



X "Recherches sitr les Acinetiens de la Cote d'Ostende," ' Bull, de I'Acad. de Bruxelles,' 1877 

 and 1878. 



