,78 GENEEAL HISTORY OF 



rudimentary antennae ; and that observer consequently appears to 

 agree with M. Dujardin, in questioning their tubular structure. 



The excellent description by Mr. Dalrymple of a new genus 

 of Motatoria — Asplanclma BrightweUii, Gosse — (Phil. Trans. 1849, 

 p. 334), affords us a very clear account of the circulatory appa- 

 ratus, diffeiing in some points from that which we have borrowed 

 from Siebold. He says, " This peculiar organ consists in a double 

 series of transparent filaments (for there is no proof of their being 

 tubes or vessels), arranged, from above downwards, in curved or 

 semicircular form; symmetrical, when viewed in front. These 

 filaments, above and below, are interlaced, loop-like ; while another 

 fine filament passes in a straight line, like the chord of an arc, 

 uniting the two looped extremities. To this delicate filament are 

 attached little tags, or appendices, whose free extremities are directed 

 towards the interior of the animal, and are afiected by a tremulous, 

 apparently spiral motion, like the threads of a screw. This is 

 undoubtedly duo to cilia arranged round these minute appendices. 

 The tags are from eight to twelve, or even twenty, in number, 

 varying in different specimens. (Plate XXIII, fig. 6a.) 



"I beKeve the organ in question to be a peculiar circulatory 

 system. The body of the animal is filled with fluid, most probably 

 analagous to blood, while the ciliated tags, in perpetual motion, must 

 produce currents in this fluid, and probably in an imiform and 

 determinate direction. In this way the nutrient plasma will be 

 brought regularly in contact vrith all parts of the body, and the 

 process of nutrition go on as in insects, without the intervention of 

 tubular vesssels, the dorsal heai't, in them, serving only to give 

 direction and circulation to the blood. I am the more impressed 

 with this belief, since these filamentous organs are in close approxi- 

 mation with the large contractile sac, which probably performs a 

 respiratory function." 



Por it win be seen, from the following extract, that Mr. Dah-ymple 

 does not believe in any communication between the sac and the 

 apparatus furnished with the ciliated tags, as Siebold supposes ; on 

 the conti'ary, the former vsniter makes the sac to communicate 

 directly with the exterior. He writes, " This sae, spherical when 

 distended, is placed just above the ovisac, and communicates ij\dth 



