GENUS S TEN TOR. 



593 



of this hypothesis is afforded by Stein's record of the occurrence of this peculiar 

 modification of the endoplast during the months only of September, October, and 

 November, or towards the approach of the winter months, when the ordinary 

 processes of reproduction by fission are frequently arrested. 



Stentor Barretti, Barrett. Pl. XXX. Fig. 21. 



Body attenuate, highly extensile, its length in full extension equalling 

 five or six times the diameter of the expanded peristome ; peristome field 

 distinctly bilobate, earshaped, the larger lobe usually elevated perpen- 

 dicularly ; fine supplementary setose appendages developed throughout the 

 body portion and around the margin of the peristome ; endoplast elon^-ate, 

 sinuous ; excreting and inhabiting an erect tubular gelatinous sheath, which 

 is usually of a light brown colour when young, but becomes darker and 

 more opaque as age advances. Length of extended body 1-25". 



Hab. — River and pond water ; solitary. 



This animalcule was first figured and described by Mr. C. A. Barrett in the 

 'Monthly Microscopical Journal' for April, 1870, as a "New Tube-dwehino- 

 Stentor," this observer there taking the somewhat unusual course of associating^ his 

 own name with its specific designation. In this original description it is reported as 

 entirely wanting the fine body cilia which characterize the ordinary species of 

 Stenfar, these being replaced by long hair-like setse ; the possession of a distinct 

 nervous system, consisting of an anteriorly located ovate body, which o-ave off 

 branches that extended down the whole length of the body, and another to the 

 expanded peristome, was also reported. If these two last-named structural charac- 

 teristics really existed, the organism described by Mr. Barrett was no Stentor, but 

 possessed a type of organization that precluded its retention among the Protozoa. 

 It was at the time, however, suspected by the author that this form represented an 

 imperfectly examined species closely allied to, if not identical with, Stentor Roeselii, 

 and in which a mucilaginous domicile and long hair-like setae are similarly developed. 

 This anticipation has been completely verified. The animalcule has been since met 

 with by a number of observers, and is included among the many interestino- infusorial 

 types that have been supplied to the author by Mr. Thomas Bolton, such examples 

 furnishing the material for the illustration of the species given at PI. XXX. Fio-. 21. 

 Through this personal examination it was soon made evident that Mr. Barrett's so- 

 called nervous system represented the imperfectly observed contractile vesicle with 

 its canal-like diverticula, while finer cilia clothing the whole body, in addition to the 

 hair-like setse, were speedily detected, thus reducing it to the structural formula of an 

 ordinary Stentor. As a trumpet animalcule, the present species is undoubtedly 

 closely allied to T. Rceselii, but manifests its distinctness from that type in its more 

 attenuate proportions, in the erect instead of horizontal comportment and distinctly 

 bilobate contour, of the peristome, in the more abundant development of the setose 

 appendages, which are produced not only from the body but from the entire circum- 

 ference of the peristome, and in the much firmer consistence of its mucilaginous 

 domicile. The examples of this species, as originally discovered by Mr. Barrett, 

 were found on water weeds taken from the river Thames at Moulsford, another 

 interesting form, referable to the genus FolTuulina, apparently F. Boltoni, being 

 likewise found in its close vicinity. 



Stentor cseruleus, Ehr. 



Body large, the width of the anterior extremity or peristomal border 

 when fully extended equal to one-third of the total length ; the substance 

 of the intermuscular longitudinal striae coloured a more or less intense blue ; 



VOL. II. K. 



