GENUS MONOSIGA. 329 



circular fringe of cilia, are furnished in addition with a long terminal flagellum, the 

 relationship maintained between these diversely modified appendages being identical 

 with that subsisting between the collar and its centrally enclosed flagellum in the 

 flagellate group now under discussion. If, indeed, future investigation were to reveal 

 that the initial condition of the ciliary wreath in these two generic types took, as in 

 other cases, the form of a simple membranous expansion, these animalcules, during 

 such earlier epoch of their existence, would be altogether indistinguishable from the 

 representatives of the ordinary Choano-Flagellata. In Asthmatos it is further note- 

 worthy that the cilia comprising the adoral wreath are of an unstable and fugitive 

 nature, being capable of protrusion and retraction after the manner of pseudopodia 

 within the substance of the body-sarcode. This particular attribute of the appendages 

 in question may be also cited as substantially supporting the affinity here inferred, 

 a similar but even more conspicuously pronounced Rhizopodal attribute being 

 exhibited by the morphologically corresponding or homologous appendage possessed 

 by the collared monads. 



As already briefly related at page 80, the animalcules belonging to this highly 

 interesting Flagellate order are remarkable for their pale glaucous green or fluorescent 

 hue, such colour assisting materially in the recognition of their presence even when 

 the magnifying power employed is insufficient for the detection of their characteristic 

 collar, with its enclosed flagellum. 



The leading demarcations of the family and generic groups of the independent or 

 Gymnozoidal section of the collared Flagellata or Discostomata adopted in this 

 volume are set forth in the accompanying Table. 



FAMILIES AND GENERA OF CHOANO-FLAGELLATA. 



SECTION I. DISCOSTOMATA-GYMNOZOIDA. 

 FAMILY. GENUS. 



I. CoDONOSiGlDjE. / [ Solitary, stalked or sessile . . I. Monosiga. 



Animalcules naked, se- Attached.. .. j United socially on a common J 2 Codosi 



creting neither a lorica / ( pedicle / 



nor a gelatinous syn- I -p. ,., mrn - / United in stellate clusters .. 3. Astrosiga. 



cytium. I ling \ United in chain-like series .. 4. Desmarella. 



II. SALPINGCECID^E. 

 Animalcules secreting 

 horny loricse. 



III. PHALANSTERIID^;. 



Animalcules secreting a 

 gelatinous zoocytium ; 

 forming extensive so- 

 cial colonies. 



Lorica solitary (Sedentary.. 5. Salpingaca. 



3 \ Free-swimming 6. Lagenceca. 



Loricae united socially and forming a branching "1 _ , 

 polythecium .. .. *>^. Polyaca. 



Collar rudimentary 8. Phalansterium. 



Collar well developed 9. Protospongia. 



Fam. I. CODONOSIGID-a:, S. K. 



Animalcules free-swimming or attached, solitary or socially united, 

 entirely naked, secreting neither independent loricae nor gelatinous zoo- 

 cytia ; collar well developed, encircling the base of the single terminal 

 flagellum ; contractile vesicles two or three in number, posteriorly located ; 

 endoplast spherical, subcentral. 



GENUS I. MONOSIGA, S. K. 

 (Greek, monos, solitary ; siga, silence.) 



Animalcules solitary, illoricate, of ovate or spheroidal contour, but some- 

 what plastic and changeable in shape, sessile or attached through the 

 medium of a simple rigid pedicle ; bearing anteriorly a well-developed 



