GENUS DENDROCOMETES. 839 



found moored to its fulcrum of support by two much smaller basal extensions, in 

 place of the more ordinary single and larger one. An example of this modification 

 is given at Fig. 34. Minute spherical freely floating Sph(zrophrya-\iik.Q organisms, 

 PI. XLVI. Fig. 35, were frequently found in the neighbourhood of these animalcules, 

 and represented apparently the earlier conditions of this species. 



Acineta dibdalteria, Parona. 



Lorica wineglass-shaped ; peduncle slender, rectilinear, about half the 

 length of the lorica ; tentacles two in number only, placed opposite one 

 another, both suctorial and prehensile, movable in all directions ; endoplasm 

 granular, more transparent at the periphery ; contractile vesicle single, of 

 large size ; endoplast horseshoe-shaped. Length of lorica 1-500". 



HAB. Salt water. 



This species is reported by Dr. C. Parona* from the Gulf of Genoa, its essen- 

 tially distinctive features consisting of the small number of the tentacles, their 

 great mobility, and adaptation to distinct functions. With reference to their mobile 

 properties, it may be mentioned that a similar character is shared by various other 

 forms, among which Acineta mystacina and Podophrya elongata, as examined by the 

 author, may be specially cited. In connection with the first-named of these two 

 species, a similar phenomenon has likewise been recently observed by Mr. F. W. 

 Phillips, of Hertford. 



GENUS X. DENDROCOMETES, Stein. 



Animalcules solitary, sessile, discoidal or subspherical ; the surface of 

 integument indurated ; tentacles slightly flexible, but not contractile, more 

 or less branched and finely perforate at their extremities. Endoplast and 

 contractile vesicle conspicuous ; increasing by internal gemmation. 



Dendrocometes paradoxus, Stein. PL. XLVIIlA. FIGS. 8-12. 



Body plano-convex or discoidal ; tentacles springing from the peri- 

 pheral margin, equal to or slightly exceeding the diameter of the body in 

 length, rarely more than five in number, usually branched in a bi-tripartite 

 manner; contractile vesicle single; endoplast subtriangular. Diameter 

 of body 1-300". 



HAB. Fresh water, on Gammarus pulex. Embryos hypotrichously 

 ciliate. 



This singular organism was originally supposed by Stein to represent an Acineti- 

 form condition of Spirochona gemmipara ; the occurrence of the two as parasites 

 or commensals of the same host, together with the circumstance that the external 

 gemmae of the Vorticellidan, in the earliest stages of their development, bear a con- 

 siderable resemblance to the internally developed ciliate embryos of Dendrocometes^ 

 affording him at that time considerable foundation for this opinion. Although 

 the independent nature of this type is now fully substantiated, its relegation to 

 this group of the Tentaculiform Infusoria has been presumably tentative and 

 provisional, no evidence having hitherto been adduced as to the use made by 

 the animalcule of its constantly extended and almost rigid tentacles, or as to what 

 manner, if any, they are subservient to the purposes of food-inception. Through, 



* 'Arch. Sci. Phys. et Nat.,' 1881, also 'Trans. Royal Mic. Soc.,' June 1881. 



