GENUS A MPHILEP TUS. 523 



entirely confirmed. The oral aperture, situated at the base of the anterior snout-like 

 prolongation, is followed by a short, conical, longitudinally plicate pharynx, as in 

 various specjes of Amphileptus, and there the oral system terminates. The more 

 granular or solid endoplasmic layer is at the same time usually developed more 

 conspicuously in a straight axial line backwards from the termination of the 

 pharynx, and receives all food-matters that pass through the oral aperture. Thus 

 physiologically, though not morphologically, it performs the part of an alimentary 

 tract. More slender ramifying diverticula from the main axial trunk are given off 

 at frequent but irregular intervals, their ultimate twigs spreading out upon and 

 anastomosing with the inner layer of the cortex. The closest resemblance to 

 this special modification of internal structure is encountered in the Flagellate 

 genus Noctiluca. In Loxodes there is no such distinct radiating disposition of the 

 internal endoplasm, this element being simply honeycombed by the intercalation 

 of irregularly developed ovate or subspheroidal lacunae. The number of contractile 

 vesicles possessed by this animalcule, while approached by Amphileptus gigas, is 

 surpassed only by the Prorodon margaritifera previously described ; they are very 

 minute, spheroidal, distributed throughout the peripheral region of the body, and 

 contract quite independently. On an average, it was estimated that as many 

 as fifty of these vacuoles were possessed by each single animalcule. Excepting for 

 the highly differentiated internal structure of the present type, it may be said to 

 accord in all essential points with the representatives of the genus Amphileptus 

 next described. 



Supplementary Species. 



The Trachdius trichopho^a of Ehrenberg, a"hd also the more recently recorded 

 Trachefais dendrophilus of the same authority, are Flagellate types referable to the 

 genus Astasia. 



GENUS II. AMPHILEPTUS, Ehrenberg. 



Animalcules highly elastic, ovate or elongate, usually more or less 

 flattened or compressed, the anterior region produced in the ferm of a trunk- 

 like appendage, at the base of which the oral aperture is situated ; cuticular 

 surface entirely and finely ciliate ; a comb- or mane-like row of longer cilia 

 often present on the inferior border of the trunk-like prolongation ; anal 

 aperture postero-terminal or subterminal ; contractile vesicles single or 

 multiple, trichocysts frequently present. Mostly inhabiting fresh water. 



A signal service has been rendered by Claparede and Lachmann by their 

 amalgamation, under the generic title of Amphileptus, of the various forms originally 

 distributed by Ehrenberg and Dujardin among the separate genera Amphileptus, 

 Dileptus, and Trachelius, all of these, with the exception of Trachelius ovum, pre- 

 senting no features sufficiently distinctive for separate generic recognition. Almost 

 all the animalcules referable to this generic group are of large size, and are easily 

 recognized by the presence of the anterior trunk-like prolongation. This appendage 

 is completely under the control of its owner, being thrust hither and thither as the 

 creature progresses through the water, or carried stiffly in an arched, neck-like 

 manner. As seen under the last-named conditions, their appearance is so forcibly 

 suggestive of that of various long-necked aquatic birds as to have won for them the 

 several specific titles of Amphileptus eygnus, anas, and anaticula. From the long- 

 necked TracJielocerccz, with which they are most liable to be confounded, the repre- 

 sentatives of the genus Atnphilepttis may be readily distinguished by the position of 

 the mouth, which is at the base instead of at the apex of the trunk-like appendage. 

 Although normally of a more or less flattened form, these animalcules frequently 

 become distorted through the inception of food, assuming under such conditions 

 a cylindrical or almost spheroidal contour. 



E 2 



