GENUS CHLORASTER. 3 1 7 



are no less than eight setose appendages delineated, representing apparently the 

 number developed preparatory to the process of longitudinal fission. 



Chic-raster agilis, S. K. PL. XIX. FIG. 15. 



Body conical or subtriangular in profile, widest and truncate anteriorly, 

 gradually tapering towards the posterior extremity, which is sometimes 

 bluntly and sometimes sharply pointed; exhibiting in transverse view a 

 quadrate outline with four symmetrically developed, projecting, keel-like 

 angles ; central vibratile flagellum slender, as long as the body, pro- 

 duced from a papilliform or pyramidal prominence that arises from the 

 centre of the frontal border ; four fine, flexible, setose flagella originating 

 close to the base of the central flagellum, which they equal in length, and 

 recurved towards the posterior extremity of the body ; endoplasm pale 

 transparent green, with a colourless central space, a faint red eye-like 

 pigment-spot usually present near one of the angles of the anterior border. 

 Length of body 1-2500". HAB. Salt water. 



This species, distinguishable from the preceding by its diminutive size and salt- 

 water habitat, was obtained in some abundance in an infusion of hay in sea- 

 water at St. Heliers, Jersey. It was first observed after the vegetable matter had 

 been macerating for a space of about four weeks, and was probably imported 

 originally with the water in the sporular condition. At first the author was disposed 

 to identify it generically, if not specifically, with the Plceotia vitrea of Dujardin : his 

 description of this form, however, in which it is described as possessing two 

 flagella only, one of which is vibrated in advance and the other trailed behind and 

 adherent at will, demonstrates the place of that species to be close to Heteromita 

 or Anisonema, and nowhere near the present type. Like Oxyrrhis, this species 

 exhibits a restless and active condition, in which it darts about too swiftly almost 

 for the eye to follow, and a sedentary one, in which the body remains perfectly 

 quiescent, and apparently angles for food with its extended vibratory flagellum. 

 The four accessory, reflected, but flexible, hair-like setae, although motionless during 

 the quiescent state, are probably brought into active use in the natatory condition, it 

 being difficult otherwise to account for the rapidity with which it, as it were, shoots 

 along in a straight line from one resting-point to another. 



The number of the setose flagella, as also the exact contour of the body, 

 whether triangulate or quadrate, proved for a considerable while a difficult point to 

 decide, but was finally settled by the addition to the water of dilute osmic acid, 

 which at once killed the animalcules without altering their shape, and thus made 

 clear the characters embodied in the foregoing diagnosis and accompanying figure. 

 Neither the existence of a contractile vesicle, of a definite oral aperture, nor the 

 inception of solid food, has as yet been determined in this species. The apparent 

 control over their motions in the water exhibited by these little beings demands brief 

 notice, and fully proves their claim for admission as representatives of the animal 

 series. In a drop of water containing several examples of this species, it was noticed 

 that if one animalcule in its swift nomadic career passed near another, possibly 

 striking it with one of its extended setae, the one so disturbed immediately started in 

 pursuit, several often joining in the chase, and gambolling together in a manner 

 corresponding with what is hereafter related of the Holotrichous Ciliate type 

 Cyclidiitm glaucoma. In a similar manner it was also observed that they would 

 congregate together in that part of the field most brilliantly illuminated by the aid 

 of the achromatic condenser, when illuminated by artificial light. In addition to 

 the faint red pigment-spot usually present at the anterior end, an oval, darkish- 

 green, nucleus-like body was frequently noticed towards the posterior extremity. 



