778 ORDER HYPOTRICHA. 



on the table, flashing out of sight after the manner of a serpula with the rapidity 

 of Hghtning. Confidence being restored, it once more makes its appearance at the 

 entrance of its abode, at first protruding a short distance only from the aperture, main- 

 taining a perfectly straight position, and with its frontal cilia quivering. No further 

 cause of alarm arising, the entire anterior half of the body is now thrust out and 

 twisted into the characteristic screw-like form depicted in the accompanying figures. 

 The tubes formed by these animalcules are described as being of very frail consistence, 

 rarely retaining their inhabitants for more than four days, and then quickly dropping 

 to pieces ; the animalcules are also exceedingly restless in captivity, deserting their 

 abodes and swimming freely in the open water without any apparent provocation. 

 The fact that the tubes are built by the animalcules themselves, and are not the 

 vacated and re-inhabited residences of Rotiferte or other tube-forming organisms, was 

 amply proved by the preservation of very young individuals possessing at the time 

 tubes whose construction had only just commenced, but which after the lapse of two 

 days exhibited all the characters and proportions of the adult types. 



Through Mr. Thomas Bolton the author received, in the years 187 1-2, from the 

 neighbourhood of Stourbridge, Worcestershire, the tubes, deserted en route, of an 

 animalcule apparently identical with this species, and upon which, guided only 

 by Mr. Bolton's sketches, and in the absence of any positive evidence respecting the 

 character of the cuticular or ventral cilia, he provisionally conferred the name of 

 Chcetospim cylindracca. This manuscript title is referred to by Mr. Bolton in the 

 'Midland Naturalist' for 1878, but the specific one, should the animalcule be a 

 veritable Stichotricha, must necessarily give way to the earlier published, though 

 later suggested, name employed by Dr. Hudson. 



Stichotricha marina, Stein. 

 This species is briefly alluded to by Stein* as closely resembling 

 5. secimda, but is of larger size, inhabits sea water, and exhibits a slight 

 difference in the arrangement of the ventral setae. 



Genus XII. SCHIZOSIPHON, S. K. 



(Greek, schizo, to cleave ; siphon, tube.) 



Animalcules structurally resembling those of Stichotricha, but forming 



social colonies which build up by excretion a compound branching tube or 



zoothecium. 



This new genus is established by the author for the reception of the interesting 

 type recently figured and described by Dr. Ernest Gruber* under the title of 

 Stichotricha socialis ; its distinctive feature, which separates it indeed from all 

 previously known Hypotricha, is manifested in the habit the animalcules have of 

 constructing by exudation a ramifying colonial habitation or zoothecium. In this 

 connection they may be said to occupy a position with relation to Stichotricha 

 corresponding with that which subsists between such compound types as Epistylis 

 or Carchesiuvi and the simple genus Vorticclla. 



Schizosiphon socialis, Gruber sp. Pl. XLIV. Figs. 4-8. 



Body elongate-ovate, obliquely truncate and attenuate anteriorly ; the 

 peristomal cilia longest at the anterior extremity, diminishing in size as 

 they approach the oral aperture, and continued up the interior or left 

 peristomal border, surmounted apically by a tuft of three or four distinctly 



* ' Infusionsthiere,' Abth. ii., 1867. 



t *Zeit. Wiss. Zool.,' Bd. xxxi., 1879; also translation iu 'Journal of Royal Microscopical 

 Society,' April 1880. 



