GENUS PHALANSTERIUM. 361 



Salpingceca inquillata, whose loricse are united to one another in systematic order 

 through the medium of their respective pedicles. As shown in the accompanying 

 figures, the more general dichotomous mode of gemmation in this species admits of 

 some slight modifications. Thus at PI. III. Fig. 28, the colony, after starting on 

 the typical plan, is continued on each side in a uniserial order, while at Fig. 20 of 

 Plate V., representing the largest colony of this species as yet met with, the right- 

 hand resultant of the primary zooid gives origin to no less than two individuals at 

 each anterior angle. Each of these, however, as is evident from the simple structure 

 of the pedicle in its proximal region, commenced as single animalcules, these, at a 

 short distance from the parent, dividing a second time by longitudinal fission. 



This highly interesting form was found attached to the hydroid zoophytes and 

 Polyzoa obtained in May 1874 from the Crystal Palace Aquarium. As with various 

 other types described in this manual derived from the tanks of large public aquaria, 

 it is impossible to predicate from what portion of the coast-line it was originally 

 imported. The correspondence of the polythecium of this species, with reference both 

 to its general mode of growth and to the contour of the individual loricae, with that 

 of the biflagellate fresh-water type Stylobryon (Poteriodendroti) petiolatum is worthy of 

 remark. 



Fam. III. PHALANSTERIID^J, S. K. 



Animalcules solitary or social, more or less ovate, bearing a single 

 terminal flagellum, the base of which is encircled by a rudimentary and per- 

 manently contracted, or by a well-developed and widely extensile mem- 

 branous collar ; excreting and inhabiting a simple or complex mucilaginous 

 protective sheath or zoocytium. 



Compared with the preceding Choano-Flagellata, the members of this family 

 group may be said to maintain a relationship corresponding with that which sub- 

 sists between the Peritrichous genus Ophrydium, and such typical Vorticellidae as 

 Vorticella, Epistylis, and Vaginicola. At the same time, the new investing element 

 or zoocytium now introduced is undoubtedly both morphologically and physiologically 

 identical with the common mucilaginous matrix or cytoblastema which enters so 

 largely into the composition of all sponge structures, and which is similarly excreted 

 and inhabited by colony-stocks of corresponding collared flagellate monads. By 

 this family group of the Phalanstcriidtz the two sections of the Discostomata- 

 Gymnozoida or naked collared monads, and the Discostomata-Sarcocrypta or slime- 

 immersed collared monads as represented by the Spongida, are beyond question 

 effectually bridged. 



GENUS I. PHALANSTERIUM, Cienkowski. 



Animalcules normally symmetrically ovate but more or less plastic and 

 variable in form, bearing a single terminal flagellum, whose base is enclosed 

 by a conical, non-extensile, hyaline collar ; endoplast and one or more con- 

 tractile vesicles usually conspicuous ; producing extensive colonies through 

 multiplication within a variously modified common gelatinous matrix or 

 zoocytium ; the flagella only projecting beyond the zoocytium into the 

 outer water. 



As originally founded by Cienkowski,* the genus Phalansterium was made to 

 include two entirely distinct flagellate forms, one of which, P. intestinum, possessing 

 two flagelliform appendages, has been selected by Stein as the type of the previously 



1 Archiv fiir Mikroskopische Anatomic,' Bd. vi., 1870. 



