GENUS DENDROSOMA. 845 



ciliated germs developed from the substance of the erect trunks were abundantly 

 observed. These in the main agree substantially with what has been recorded by 

 Mr, Levick, though in some {q\n details the author is in a position to supply new 

 data. Thus with the aid of picrocarmine it was demonstrated that the endoplast or 

 nucleus, not recognized in either the adult or embryonic state by Mr. Levick, is 

 already well developed and more or less ramified by the time the embryo has 

 developed its first erect tentaculiferous ramuscule, and moreover that short capitate 

 tentacles are produced irregularly from all parts of the free periphery prior to the 

 appearance of the early bud-like outgrowth of this stem, and are retained for a 

 considerable interval after its appearance. These several points are fully illustrated 

 in Figs. 19-22 of the Plate already quoted. It is there shown, see Fig. 22, that 

 one branch of the endoplast is developed towards and finally ascends the initial 

 stem, while the other branches follow the various directions of growth taken by the 

 adherent stolon. As indicated in the same figures, a number of contractile vesicles 

 are developed not only in the initially fixed but also in the free-swimming condition 

 of the ciliated embryos. 



Attention may be suitably directed at this point to the very considerable resem- 

 blance that subsists between that early developmental phase of Dendrosoma radians, 

 in which it consists simply of a flattened adherent body out of which is produced a 

 single erect stem with its apical sheaf of tentacles, and the normal condition of the 

 proboscidiform zooids of an Ophryodmdron such as A. scrtidaricz, assuming that the 

 proboscidiform organ with its terminal cirri is homologous with the erect stem 

 and tentacular sheaf of the first-named type. It is recorded by Mr. Levick that the 

 growing terminations of the branches of the adult colony-stocks of Dendrosoma 

 radians are not only soft and plastic, but highly polymorphic, the granular particles 

 of its component protoplasm flowing from one part to another and altering the 

 contour much after the manner of the body of an Avia;ba. Such plasticity is, how- 

 ever, by no means characteristic of the fully matured parts, throughout which the 

 author has satisfied himself that a distinct cuticular membrane is developed, such, 

 indeed, showing under high magnifying power, as treated with osmic acid and 

 picrocarmine, a conspicuously marked double contour. In its first-formed condition 

 it is nevertheless soft and tenacious, permitting the adhesion of foreign bodies, 

 which are often present in such quantity as to entirely preclude distinct vision 

 of its true limits. 



The author has very recently, March 1882, obtained fine examples of this 

 interesting type, through Mr. F. J. Fry, from a pond in the neighbourhood of Clifton, 

 Bristol, its tolerable abundance in the same neighbourhood having been further 

 certified to the author by Dr. C. T. Hudson. Among the nearly allied associates 

 of this type observed by the author in connection with the specimens remitted from 

 Birmingham may be more especially mentioned Acineta grandis, A. lemnarujn, 

 and A. mystacina var. longipes. Professor Leidy* has reported the occurrence of 

 Dendrosoma radians in American waters. 



Dendrosoma Astaci, Stein. 



Under the above title. Stein t briefly refers to a species of Dendrosoma found 

 by him attached to the fresh-water crayfish, Astacus fluviatilis. No characters, 

 however, have as yet been cited by which it may be distinguished from the preceding 

 type, and taking into consideration the usually fluviatile habitat of D. radians it 

 would seem highly probable that the two are identical. 



* ' Proc. Acad. Nat. Hist. Philadelphia,' 1874. 



t ' Der Organismus der Infusionsthiere,' Abth. i. p. 93, 1859. 



