842 ORDER TENTACULIFERA-SUCTORIA. 



eating mostly at angles of from 30 to 50 degrees from the main stem, but not 

 unfrequently decussating at right angles or even reflected backwards, their 

 extreme ends usually slightly dilated ; tentacles distinctly capitate, highly 

 extensile, developed in a sheaf-like or fasciculate manner from the slightly 

 dilated terminations of the ramuscules ; contractile vesicles numerous, 

 spherical, irregularly distributed throughout the main stem and secondary 

 branches ; endoplast ribbon-like, ramifying and much contorted in the stolon 

 and basal portions of the main stem, continued as a simple band into the 

 distal region and secondary branchlets ; endogenous, hypotrichously ciliated 

 embryos of relatively large size developed in nodular enlargements of the 

 main stem or primary branchlets ; more minute, pyriform, tentaculiferous 

 germs produced by gemmation towards the terminations of the ultimate 

 branchlets. Height of adult colony-stock 1-25" to i-io"; average diameter 

 of tentaculiferous distal terminations 1-500". 



HAB. River and pond water, on Anacharis, Myriophyllum, and other 

 aquatic plants. 



Dendrosoma radians was originally described by Ehrenberg * as a compound 

 species of Actinophrys ; Perty, Dujardin, and other contemporary investigators 

 placed it on Ehrenberg's authority in the same category, while Pritchard, in his 

 'History of the Infusoria,' p. 562, 1861, suggested the probability of its being 

 more nearly allied to Anthophysa. Claparede and Lachmann, who were the first to 

 carefully re-examine this organism, at once recognized its Acinetan affinities, and 

 described it at length, with an accompanying highly characteristic illustration, in 

 their well-known ' Etudes sur les Infusoires,' published in the ' Memoires de 

 1'Institut Genevois,' between the years 1858 and 1860. These investigators, never- 

 theless, failed to recognize, or rather misinterpreted, certain of the more important 

 structural features of this species, and were altogether unacquainted with any 

 phenomena of propagation apart from those connected with the increase in dimen- 

 sions of the parent colony by repeated fission of the terminal branches, or by 

 the outgrowth of the creeping stolon or main trunk. The chief error committed 

 by these authorities consists of the fact that they figured and described the con- 

 tractile vesicle as a long canal-like lacuna, extending throughout the substance of 

 the main trunk, with offshoots to the secondary branches, and having spherical 

 dilatations at irregular intervals. The nucleus or endoplast was at the same time 

 entirely overlooked, or its outline apparently mistaken for that of the so-called 

 contractile vesicle. Both of these last two structures, while not referred to in 

 Ehrenberg's original description, are distinctly indicated in his drawings, then 

 mislaid but subsequently published in the ' Abhandlung der Berliner Akademie ' for 

 the year 1862. Stein, who was also personally acquainted with this form, fully 

 recognized its true position, and rightly interpreted its structural characters in a 

 brief reference made to it in the first volume of ' Organismus ' (p. 90, 1859), but adds 

 nothing with reference to the phenomena of reproduction. The honour of placing 

 on record the first authentic account of the propagation of Dendrosoma radians by 

 any other method than that of the outgrowth of the parent stock belongs to 

 Mr. J. Levick, of Birmingham. This microscopist has published, in the ' Transac- 

 tions of the Birmingham Natural History Society' for the year 1880, an account, 

 with accompanying illustrations, of a prolonged examination of this species, and in 

 the course of which he observed the release of ciliated embryos from the parent- 

 stock, and their attachment and development of tentaculate appendages. Mr. Levick 

 further describes what he interprets to be the propagation of this species by a 

 distinct genetic process, capsular bodies being produced as outgrowths of the stem 



* ' Die Infusionsthierchen,' 1838. 



