660 ORDER PERITRICHA. 



immediately beneath the peristome-border. Animalcule when retracted 

 bent to one side and transversely puckered on its shorter concave border, 

 the anterior margin projecting centrally as a small snout-like prominence. 

 Dimensions unrecorded. HAB. Fresh water, on Nais. 



No complete diagnosis of this species is given by D'Udekem * in his brief 

 reference to it under the title of Gerda inclinans, he being rather doubtful whether or 

 not to regard it as a variety only of either the Scyphidia ringens of Dujardin or as 

 the single and immature condition of his own Epistylis Jubifids. The excellent 

 figure, however, that accompanies his brief description, and in accordance with 

 which the present diagnosis is framed, leaves no doubt as to the specific distinction 

 of this type from either of the two forms mentioned. Its occurrence abundantly 

 always as separate individuals, apart from the basal sucker, sufficiently distinguishes 

 it from the Epistylis, while the smooth surface of the integument assists in separating 

 it from Dujardin's type. 



GENUS III. SPIROCHONA, Stein. 



Animalcules solitary, elongate-fusiform or campanulate, attached pos- 

 teriorly by an adherent sucking-disc or acetabulum ; peristome developed 

 wholly or in part as a hyaline, spirally convolute, membranous funnel, 

 the right or left limb of which descends into the oral fossa ; endoplast 

 ovate or elongate ; increasing by gemmation or transverse fission. Inhabit- 

 ing fresh, salt, or brackish water. 



The remarkable funnel-shaped modification of the anterior region in this and 

 the succeeding genus may be regarded as an exaggerated development of the 

 membranous collar-like extension of the peristome-border in Opercularia and Lage- 

 nophrys hereafter described. All the species so far discovered occur as parasites 

 or commensals upon other aquatic animals. To the two forms originally introduced 

 by Stein a third, S. tintinnabulum is here added. 



Spirochona gemmipara, Stein. PL. XXXIII. FIGS. 43-49. 



Body elongate-fusiform, narrowing at both extremities, attached pos- 

 teriorly by a circular, radiately striate, adhesive disc ; peristome contracted 

 at its base, produced into an elevated, funnel-shaped, spirally convolute 

 lamina of three turns, whose height nearly equals that of one-half of the 

 entire body. Length of body 1-750" to 1-216". 



HAB. Fresh water, attached to the ova-capsules of Gammarus pulex 

 and various Entomostraca. 



The structure and development of this species is the subject of a valuable 

 communication contributed by Professor R. Hertwig to the ' Jenaische Zeitschrift,' 

 Bd. ii., 1877, in which it is shown that the animalcule is adherent to its fulcrum 

 of support through the medium of a special sucker-like modification of its basal 

 extremity, in place of being mounted on a short and simple pedicle, as originally 

 described by Stein. The production of new zooids by gemmation is accompanied 

 by the separation and embodiment within the gemma of a portion of the parent 

 endoplast, an exhaustive account being given by Hertwig of the successive aspects 

 exhibited by the bud during its growth to the adult form. Certain of these phases, 

 as shown at PI. XXXIII. Figs. 45 and 46, resemble in a remarkable manner such a 



* ' Infusoires de la Belgique,' 1864. 



