5 1 6 ORDER HOLOTRICHA. 



spends with the normal aspect of this region in the present species. Claparede and 

 Lachmann observe of the terminal oral region of this animalcule that the circlet of 

 oral cilia is capable of being adpressed against the distal extremity, and assists in 

 the prehension of food-particles. Under high magnification the walls of the conical 

 oral fossa are shown to be longitudinally striate, and are probably plicate in a 

 manner closely corresponding, though in a more marked degree, to what obtains in 

 the two genera Trachelophyllum and Enchelyodon. 



In a gathering containing this animalcule, T. olor, in abnormal abundance, 

 examined by the author so recently as February 1880, it was observed that a form 

 corresponding in external contour with the marine Lacrymaria lagenula of Claparede 

 and Lachmann, was equally plentiful; furthermore, that every intermediate con- 

 dition, having gradually lengthened and more or less flexible neck-like prolonga- 

 tions, were intermingled, the two extreme forms being thus closely amalgamated with 

 one another. Finally, by patient watching, the short, stiff-necked Lacrymaria-\\k.Q 

 zooids were found to develop into the long and graceful necked Trachdocercce, the 

 primary simply flask-shaped zooid gradually acquiring a distinct attenuate and 

 extensile neck, the two being thus demonstrated to be transitional phases only of the 

 same species. The observation of this type being still further prolonged, it was at 

 length determined that the short-necked zooids were the derivatives by transverse 

 fission of an ordinary long-necked animalcule, and represented the hinder moiety of 

 the fissive process pending the subsequent rapid development of the characteristic 

 neck. . 



Trachelocerca versatilis, Mull. sp. PL. XXVII. FIG. 33. 



Body attenuate fusiform, pointed posteriorly ; neck long and thread- 

 like, its distal extremity expanded and conspicuously ciliated underneath ; 

 cilia of the general cuticular surface exceedingly fine and difficult to detect. 

 Length, when extended, 1-40"; retracted, 1-120". 



In the autumn of the year 1870, a salt-water species of Trachelocerca was obtained 

 by the author at Bognor, Sussex, evidently identical with the form briefly characterized 

 as above by both O. F. Miiller and Dujardin under the respective titles of Trichoda 

 and Lacrymaria versatilis. Unfortunately, the amount of attention requisite for the 

 framing of a more complete diagnosis was not bestowed upon it at the time. 

 Compared with T. olor, with which Perty has proposed to identify this species, it 

 may, however, be stated that the body was much more narrow and attenuate, and 

 the distal extremity of the neck or oral region proportionally thicker ; the subter- 

 minal circle of oral cilia was likewise observed to be more obliquely set, a circum- 

 stance communicating to this region, when seen in profile, the aspect of being 

 ciliated underneath, attested to by the authorities quoted. In the great length and 

 elasticity of the neck-like prolongation this species rivals the form previously 

 described. 



The salt-water Trachelocerca sagitta of Ehrenberg, briefly described as of fusiform 

 contour, with a very long neck, colour white, head terminal and opaque, length 120", 

 would seem to correspond closely with Trachelocerca versatilis, or may be identical 

 with Cohn's T. phcenicopterus. 



Trachelocerca phcenicopterus, Cohn. PL. XXVII. FIG. 32. 



Body elongate, ribbon-like, flattened, highly elastic and retractile, finely 

 annulate transversely, prolonged anteriorly into an attenuate, trans- 

 parent neck, and posteriorly into a long, pointed, tail-like portion ; oral 

 aperture terminal, circular, with a rigid annular border, followed by a funnel- 

 shaped pharyngeal cleft ; the distal end of the neck slightly widened, its 





