GENUS MONOSIGA. 33 I 



occasionally observed, the majority of examples were fixed directly to the water- 

 weed without any such intermedium. This diverse character of the mode of attach- 

 ment of the individual zooids finds its parallel in the loricated type Salpiiif^oeca 

 amphoridiuin, where also a short pedicle may or may not be developed. A colony 

 of this species was first discovered attached to decaying leaves of Valisneria from 

 a fresh-water aquarium, and has been subsequently met with clustered in a similar 

 social manner upon the carapace of a species of Cyclops taken from a mill-pond 

 in St. Peter's Valley, Jersey. 



At Figs. 20 and 21 of PI. IV. two zooids are represented which, having with- 

 drawn their collars and flagella, have assumed a semi-amoebiform contour, while the 

 endoplasm has become highly vacuolar. 



Monosiga Steinii, S. K. Pl. IV. Fig. 12. 



Body elongate-ovate or subfusiform, widest centrally, tapering evenly 

 towards each extremity, about twice as long as broad, attached imme- 

 diately by its pointed posterior termination to the chosen fulcrum of 

 support ; collar nearly equalling the body in height ; contractile vesicle 

 single, posteriorly situated ; endoplast inconspicuous. Length of body 

 1-1600". 



Hab. — Fresh water, attached to the pedicle of Vorticella convallaria. 



Some half a dozen zooids of this species are figured by Stein * as doubtful phases 

 of Codosiga boiijtis, attached to the contractile stalk of a single example of the 

 Vorticellidan above named. The even fusiform contour of the body, and entire 

 absence of a pedicle, serve to distinguish this type from M. b/rvipes, which it other- 

 wise most nearly resembles. A species apparently identical with this form has 

 been recently observed by the author attached to the branching pedicle of Epistylis 

 plicatilis. 



Monosiga fusiformis, S. K. Pl. IV. Fig. 17. 



Body elongate-fusiform, widest centrally, tapering and attenuate at each 

 extremity, about three times as long as broad, fixed by the posterior 

 extremity without any intermediate pedicle ; contractile vesicles two in 

 number, posteriorly located; endoplast subcentral. Length 1-2500". 



Hab. — Pond water, gregarious. 



Examples of this species were found congregated upon the carapace and ovisacs 

 of a species of Cyclops obtained from one of the water-fowl ponds in the Zoological 

 Gardens, Regent's Park, in May 1879. Its more attenuate contour and crowded 

 habit of growth distinguish it from Monosiga Steinii. 



B. — Pedicle conspicuously and persistently developed. 



Monosiga gracilis, S. K. Pl. II. Fig. 3, and Frontispiece. 



Body elongate-ovate, broadest anteriorly, attenuate posteriorly, about 

 two and a half times as long as broad, seated on a pedicle of from three to 

 four times the length of the body, distal extremity of the pedicle retaining 

 its original plastic state for a length nearly equalling that of the body. 

 Length 1-4000". Hab. — Salt water. 



This species was obtained by the author in November 1875, attached to the 

 stems of hydroid zoophytes and sea-weeds from the Manchester Aquarium, and also 



' Infusionsthiere, ' Abth. iii., 1878. 



