as a Craspedote Flagellate Infusorian. 81 



direct observations, in this respect, strictly apply to the latter. 

 It is more likely that ours is a different genus from the Sj^on- 

 gilla of Carter, in favour of which we cite the curious fact that 

 each aperture in the inner division (not mentioned by Carter) 

 of the investing membrane exactly overlies and is inseparable 

 from the entrance to a monad-chamber ('' ampullaceous sac,^^ 

 _partim, Carter) ; so that whatever enters these chambers must 

 go out by the same way that it came in, not out into a system 

 of branching canals burrowed in the monadigerous mass, but 

 into the great circulatory apartment. 



EXPLANATION OF PLATE XI. 



Spo7iffilla arachnoidea, Jas.-Cl. 



The following letters apply to identical parts in all of the figures : — a, 

 investing membrane, outer division ; a', sectional profile of the cyto- 

 blastema of « ; b, cells in the thickness of «; i', cells (like those at h) 

 about the spicules (e) ; h~, cells of the investing membrane -with their 

 nucleus, a sm-face \dew ; b^, temporary junction (by contact only) of 

 the outer [a) and inner (c) divisions of the investing membrane ; c, in- 

 vesting membrane, epithelioid imier division, in sectional profile ; c^, in- 

 terspaces between monad-chambers; f/, junction of the divisions of the 

 investing membrane along the spicules ; e, larger spicules ; e', smaller 

 spicules ; f, circulatory apartment ; g, monadigerous mass ; h, monad- 

 chambers and monad groups ; i, aperture of h ; j, monads, or the body 

 proper in figs. 3 and 3 a ; k, cylindrical collar of j ; I, flagellum ; m, 

 nucleus ; os, minor ostioles ; v, contractile vesicles. 



Fiy.l. Magnified 320 diameters. Part of a very young <S/ja«^27/«, of an 

 oblate spheroidal form, and about .}-^ of an inch in diameter. 

 On the right is presented a face view of the investing membrane 

 and the underlying monadigerous mass. On the left the focus 

 is so adapted as to be fixed on a face view of the monad mass, 

 and at the same time on a sectional profile of the investing mem- 

 brane at a\ h^, c, and d. 



Fig. 2. Magnified 780 diameters. Interior of a monad-chamber seen 

 through the aperture ; the monads appear in end i-iew and 

 crowded together side by side like a pavement-work. 



Fig. 3. Magnified 1000 diameters. A single monad, as seen in profile 

 in the monad-chamber. Only two contractile vesicles were 

 present in this specimen. The cylindrical collar (k) is extended 

 to its utmost. 



Fig. 3 a. Magnified 1600 diameters. Foreshortened front view of a 

 monad ; the body (./) in the distance ; the hollow cylinder (k) 

 projecting toward the observer like a dark hoop, and ihejiagelkwi 

 (/) in the centre appearing as a black spot. 



Fig. 4. Magnified 780 diameters. Sectional view of a monad-chamber, 

 bringing the aperture (i) into profile, as well as the monads 

 which lie at the same level, thus sho-^ving their convergence 

 about the central open space. 



Ann. (£) Mag. N. Hist. Ser. 4. Vol. ix. 



