as Infusoria flagellata. 193 



demonstrated in two ways at least. In the first place, it is 

 hig-hly flexible and retractile, as it occasionally shows itself to 

 be, either by narrowing its aperture almost to absolute closure 

 (fig. 24, b), or by reducing its height to a small fraction of its 

 greatest altitude (as seen in fig. 27, b), and then extending it- 

 self again, within a few seconds, by a direct protrusion (fig. 26,^), 

 to its original proportions (fig. 25, b). In the second place, it 

 divides longitudinally, like the rest. of the body, when self- 

 division occurs (figs. 11-22) — a process in which no genuine 

 calycle was ever known to be concerned. In an adult state 

 (figs. 8, 11, 24% 25) it is slightly constricted by a gradual in- 

 curvature extending from the base (fig. 24^, b^) to the distal 

 margin {b^) ; but frequently, and apparently always just before 

 self-division takes place, its sides bulge slightly outward (fig. 

 11, b). Taking all these things into consideration, therefore, 

 it is perfectly clear that this infusorian is not a calyculate form, 

 but one of those mimetic shapes which occasionally deceive 

 the eye and puzzle the observer, until he becomes familiar with 

 their various phases of growth and development. 



This phenomenon is most singularly exemplified by the 

 creature before us now, in its almost indistinguishable resem- 

 blance to a genuine calyculate Flagellifer {Saljnngmca mm-ina, 

 PL VI. figs. 28-32^) which abounds in our marine waters. 

 This similarity arises chiefly from the fact that the urceolus 

 (figs. 28-32, c) of the latter has an oval shape like the body 

 of the former, and is constricted so closely at its aperture (c^) 

 as to present the appearance of being continuous Avith the high 

 campanuliform collar (b) which projects from the front. Usu- 

 ally, however, the body ^^roper of this animal {Scdinnya'ca 

 marina^ nov. sp.) lies loosely within, and considerably with- 

 di-awn (fig. 28) from, the parietes of its calyx ; but occasionally 

 in older specimens it completely fills (fig. 31) its sheath ; and 

 then it is next to impossible to distinguish it, in this respect, 

 from a Codosiga. In a sessile freshwater species of SaljJin- 

 gaeca of the urceolate type {S. amjyJioridmm, figs. 37-37''), 

 the resemblance to Codosiga is almost as strong, but the dif- 

 ference is equally marked. 



The fagellum (figs. S&c.,fl) is the only prehensile organ 

 which Codosiga possesses. It arises from the middle of the 

 low truncate cone ( //•) which constitutes the front, and con- 

 sequently within the campanulate collar (b), reminding one of 

 the cm-vate stgle of a labiate monopetalous flower. It is usu- 

 ally rigid, excepting at the tip, which is constantly occupied 

 in throwing particles of various kinds toward the mouth (m) 

 by vigorous spasmodic incurvations or jerks. At its basal half 

 it is slightly curved towards the longer side of the body, but 



