MICKOSCOPIC FORMS OF ANIMAL LIFE. 



61 



FIG. 312. 



cilia of Polyzoa. 1 In fact, they seem rather to deserve the designation 

 of setcB (bristles); for "their action is spasmodic, it creates no vortex, 

 and it is only by actual contact with these setce that floating particles are 

 whipped within the area inclosed by the lobes, where by the same whip- 

 ping action they are twitched from point to point irregularly downwards, 

 until they come within the range of a vortex that is due, not to any 

 action of the setce, but to a range of minute cilia in the funnel ." 2 A 

 careful comparison of Stephanoceros with other forms, 

 shows that its tentacles are only extensions of the 

 ciliated lobes which are common to all the members 

 of these families; and the cylindrical ' cell ' which en- 

 velops the body is formed by the gelatinous secretion 

 from its surface, thrown-off in rings, the indications 

 of which often remain as a series of constrictions. In 

 respect of the length of the filaments projecting from 

 its lobes, and the breadth of these expansions, Flos- 

 cularia is still more aberrant. The body of Melicerta 

 is protected by a most curious cylindrical tube, com- 

 posed of little rounded pellets agglutinated together; 

 this is obviously an artificial construction, and the 

 process by which it is built may be watched by any 

 Microscopist who is fortunate enough to capture it. 3 

 Beneath a projection on its head, there is observed a 

 small disk-like organ, in which, when the ' wheels ' 

 are at work, a movement is seen very much resembling 

 that of a revolving ventilator. Towards this disk the 

 greater proportion of the solid particles that may be 

 drawn from the surrounding liquid into the vortex of 

 the wheel-organs, are driven by their ciliary movement, 

 a small part only being taken into the alimentary 

 canal; and there they accumulate until the aggrega- 

 tion (probably cemented by a glutinous secretion fur- 

 nished by the organ itself) acquires the size and form 

 of one of the globular pellets of the case; the time 

 ordinarily required being about three minutes. The 

 head of the animal then bends itself down, the pellet- 

 disk is applied to the edge of the tube, the newly- 

 formed pellet is attached there, and, the head being lifted into its 

 former position, the formation of a new pellet at once commences. 

 Another curious example of this family is presented by the Conochilus 

 volvox; which is found in spherical clusters composed of a considerable 

 number of individuals adherent by their tails, their bodies being arranged 

 in a radiating manner, and the intervals between them being filled up by 

 a gelatinous substance. There is not, however, any such organic connec- 



1 In ordinary drawings, the filaments of the Stephanoceros are represented as 

 short bristles; this is an error arising from bad instruments or defective illumina- 

 tion. It requires considerable skill to show these filaments, or those of the FJos- 

 CMlaria, in their true length; but the beauty of the object is geatly increased 

 when this is accomplished. 



' 2 See Mr. C. Cubitt's ' Observations on the Economy of Stephanoceros,' in 

 ' Monthly Microsc. Journ.," Vol. iii. (1870), p. 242. 



a See Gosse ' On the architectual instincts of Melicerta ringens,' in ' Trans, of 

 Microsc. Soc.," Vol. iii. (1852), p. 58; also Bedwell in ' Monthly Microsc. Journ.,'" 

 Vol. xvi. (1877), p. 214; and Hudson in " Journ. Roy. Microsc. Soc.," Vol. ii. (1879), 

 p. 1. 



Stephanoceros Eich- 

 ornii. 



