GENUS ENCHELYS, 509 



one-third of its entire length from the anterior extremity ; trichocysts large 

 and conspicuous, irregularly disposed (?) ; endoplasts two in number, 

 elongate-ovate, placed usually one behind the other; contractile vacuole 

 posteriorly situated. Multiplying by transverse fission. Length 1-200". 

 HAB. Salt water, Norwegian coast, and also at Kiel in brackish water. 



This single representative species of the genus Polykrikos as established by 

 Biitschli, accords so closely in general contour, and in the position of the mouth, with 

 the members of the genus Coleps, the annulation of the cuticle more particularly ap- 

 proximating that of C. amphacanthus, that it appears desirable to retain it provisionally 

 in the same family group. The long seta projecting from the oral cleft is possibly 

 the homologue of the seta common to various members of the Hypotrichous genus 

 Trochilia. The feature usually regarded as the most abnormal and important in this 

 type is the enormous size of the contained trichocysts and the perfect correspondence 

 of these structures with the nematocysts or thread-cells of the Crelenterata or sea- 

 anemones and hydroid zoophytes. The impression conveyed by a reference to 

 Butschli's original description and drawings of these structures,* reproduced at 

 PI. XXVII. Figs 9 and 10, are, it must be confessed, not unmingled with the 

 suspicion that these so-called trichocysts have an entirely adventitious origin. Their 

 disposition within the interior of the endoplasm is altogether irregular, and such as 

 would occur if incepted as food-material. The species, furthermore, possesses 

 a marine habitat, and not improbably feasts upon the debris of defunct zoophytes in 

 the same manner as the more familiar Coleps hirtus preys upon the residual 

 detritus of fresh-water organisms. The thread-cells of the Coelenterate structures 

 would in the former instance be extensively engulfed, and would, under such 

 circumstances, present the aspect accredited to them by Biitschli. Until, therefore, 

 further evidence is forthcoming proving the extrusion of these so-called trichocysts 

 from the cuticular surface of Polykrikos, their admission in the foregoing diagnosis 

 must be regarded as purely provisional. 



Fam. V. ENCHELYID^E, S. K. 



Animalcules free-swimming, more or less ovate, ciliate throughout, oral 

 cilia slightly larger than those of the general cuticular surface ; cuticle soft 

 and flexible ; oral aperture terminal or lateral ; the anterior extremity of 

 the body never prolonged in a neck-like manner. 



The group of the Enchelyidae, as here defined, while corresponding to some 

 extent with that of the Enchelia and Enchelina of Ehrenberg and Stein, has a much 

 more restricted limitation, the long extensile-necked Trachelocerca, Prorodon and its 

 allies, and Coleps with its indurated integument, being excluded and referred to 

 independent families. 



GENUS I. ENCHELYS, Ehrenberg. 



Animalcules free-swimming, elastic and changeable in shape, pyriform 

 or globose ; oral aperture situated at the termination of the narrower and 

 usually oblique truncate anterior extremity ; anal aperture at the opposite 

 or posterior termination ; surface of cuticle entirely but very finely ciliate ; 

 cilia longer and more easily distinguishable in the region of the mouth. 

 Inhabiting marsh and stagnant water. 



* ' Archiv fur Mikroskopische Anatomic," Bd. ix., 1873. 



