564 ORDER HOLOTRICHA. 



been since successfully demonstrated by Professor E. Ray Lankester.* As inti- 

 mated by this last-named authority, a satisfactory exhibition of these structures in 

 their natural condition is best attained by examining the creatures immersed within 

 the intestinal fluids of the host they infest. Placed in pure water the pulsating 

 action is at once suspended, while by the process of endosmosis their form and 

 character becomes entirely metamorphosed. A species apparently identical with 

 the present one, but of much larger size, 1-50", was obtained by Professor Lan- 

 kester from a species of Lumbriculiis ; no less than thirty contractile vesicles were 

 observed in some of the larger examples of this variety. 



Anoplophrya nodulata, Midler sp. 



Body elongate-ovate or elliptical, usually somewhat widest anteriorly ; 

 cuticular surface longitudinally striate ; entirely and finely ciliate ; endoplast 

 axial, band-like ; contractile vesicles numerous, forming a linear series on 

 each side of the band-like endoplast. Length 1-200". 



Hab. — Marine, within the intestine of Nais littoralis. 



This species, more generally known by the name of Opalina Ihieafa, conferred 

 upon it by Max Schultze,| is undoubtedly identical with the type inhabiting the 

 same host figured and described by O. F, Miiller, ' Zoologia Danica,' 1788, under 

 the title of Leucophrya nodiclata. This earlier investigator has not only clearly 

 indicated in his drawings, loc. cit. Taf. Ixxx.figs. rt!-/, the respective contours and plan 

 of disposition of the central endoplast and double line of contractile vesicles, but 

 also attests to the manner of multiplication through the separadng-off of a small 

 nodular segment only of the posterior region of the body. Sometimes two imper- 

 fectly separated segments are recorded as remaining consentaneously attached to 

 the primary zooid, such reproductive phenomenon preparing the way for the very 

 remarkable modificadon of the process that obtains in the species next described. 



Anoplophrya prolifera, C. & L. sp. Pl. XXVI. Fig. 14. 



Body elongate-linear, widest anteriorly ; cilia of cuticular surface dis- 

 posed in longitudinal lines in correspondence with the superficial longi- 

 tudinal striations ; endoplast axial, elongate, subcylindrical ; contractile 

 vesicles numerous, disposed in two longitudinal rows, one on each side 

 of the central endoplast ; increasing by multiple transverse segmentation 

 of the posterior body-half. Length 1-70". 



Hab. — Within the intestinal cavity of various marine Annelids, Norwe- 

 gian coast. 



This species, described by Claparede and Lachmann under the title of Opalina 

 prolifera, is acknowledged by them to so closely resemble the O. lincata of Schulze 

 (Miiller's Leucophrya nodulata) as to be possibly identical with that type. A most 

 remarkable feature of this form, however, and one which seemed to justify its 

 description by Claparede and Lachmann as a distinct form, is connected with 

 its mode of increase. This is effected by muldple instead of by simple transverse 

 fission, the posterior portion being often, as shown in the accompanying figure, 

 divided into as many as five nodular segments, each of which becomes consecutively 

 separated oft" to form an independent zooid. This singular mode of muldplicadon, 

 while occurring in no other known member of the Infusorial class, is highly charac- 

 teristic of what obtains among certain lower Annelida, such as Syllis or Nais, 



* ' Quarterly Journal of Microscopical Science,' p. 143, 1870. 



t ' B^citriige zur Naturgeschiclite cler TurbcUaricn,' Greifswalde, 185 1. 



