GENUS ASTROSIGA DESMARELLA. 341 



GENUS III. ASTROSIGA, S. K. 



(Greek, astron, star; siga, silence.) 



Animalcules naked, free-swimming, united by their posterior extremities 

 so as to form compound stellate or subspheroidal clusters ; anterior region 

 bearing a single long terminal flagellum, whose base is encircled by a well- 

 developed, extensile and contractile, hyaline collar. 



Astrosiga disjuncta, From sp. PL. II. FIGS. 12 AND 13. 

 Zooids fusiform, tapering posteriorly, and there united to one another 

 by the attenuated and almost pedicle-like elongations of the body-substance 

 of this region. Length of zooids i-i 600". HAB. Freshwater. 



The new generic title conferred upon this species has been established by 

 the author for the reception of the form figured and described by De Fromentel * as 

 a species of Uvella. In his description, which is most meagre, and also in his 

 illustration, each unit is represented as bearing three short flagella, which, from their 

 position and direction, it is evident represent a central flagellate appendage and the 

 two lateral margins of the hyaline infundibulate collar of a typical collared animalcule, 

 as seen under inadequate magnification. The figure given by De Fromentel is repro- 

 duced at PL II. Fig. 12, as also another representation, Fig. 13, slightly enlarged 

 from this, with the anterior margin of the collar, which escaped that authority's 

 notice, alone filled in. The example figured represents a stellaeform colony composed 

 of five zooids only, but doubtless much larger ones exist. Taken collectively, the 

 colony-stocks of this specific type present a close resemblance to the monad-clusters 

 of Codosiga botrytis separated from their common footstalk and floating freely in the 

 water after the manner of the detached monad aggregates or " coenobia " of 

 Anthophysa vegetans. The more attenuate contour of the constituent monads of 

 Astrosiga at the same time precludes the inference that might otherwise be arrived 

 at, that it represents a detached colony of the first-named species. 



GENUS IV. DESMARELLA, S.K. 



(Dim. of Greek desmos, chain.) 



Animalcules naked, free-swimming, forming compound colonies, and 

 united to one another by their lateral surfaces, without the intermedium of 

 a pedicle or other supplementary element. Flagellum single, terminal, its 

 base encircled by a well-developed, extensile and contractile, hyaline 

 collar. 



This and the preceding genus constitute the only free-swimming compound 

 colony forms of the Choano-Flagellate order as yet discovered, though further 

 investigation will probably lead to the recognition of as large a number of varieties 

 as are here shown to obtain among the sedentary species. 



Desmarella moniliformis, S. K. PL. II. FIG. 30. 



Zooids symmetrically ovoid, arranged in single chain-like series, each 

 colony-stock containing from two to as many as eight individual units ; 

 endoplast spherical, subcentral ; contractile vesicles two or more in number, 

 posteriorly located. Length of individual zooids 1-4000". 



HAB. Salt water. 



* 'Etudes sur les Microzoaires,' Paris, 1876. 



