510 JOSEPH STAFFORD, 



From the excretory pores round to the place where ciliary organs 

 begin each stem is simple but soon after this it becomes complicated 

 through its branching. In the fore part of the body each trunk gives 

 0Ö a branch which turns forwards into the neck and oral regions. 

 Farther back — not far from the middle length of the animal — 

 there is a division of each main tube into three : one proceeding back- 

 wards continuous with the main, one turning upwards, outwards and 

 backwards and the third downwards, outwards and forwards. After 

 a short course from this first tri - radiate branching each member 

 undergoes a second tri-radiate division and , of course , after each 

 subdivision, the individual members are reduced in diameter and the 

 territory of each group is, in the main, marked out by the direction 

 of its mother stock. The division by threes is repeated six times, 

 and the final twigs of the system are terminated each by a funnel 

 organ (Fig. 15, 24). 



I shall not attempt to give a detailed account of each branch or 

 set of branches. I can not be sure of the absolute position of these. 

 They can of course only be followed under especially favorable con- 

 ditions and when the animal is so far compressed that, as to form 

 and relations of parts, it is extremely disfigured. Moreover, although 

 I have often found the system regularly formed as described yet 

 sometimes there were irregularities or exceptional constructions. 



Previous investigations have exhibited no symmetry in the arrange- 

 ment of the two lateral systems, nor any indications of a tendency 

 to subdivide at regular intervals and in definite numbers. This pro- 

 bability broke upon me from the fact that wherever I could follow 

 with certainty the fine branches I found three funnel organs arranged 

 in radial order on capillaries that si)rang from a common centre. 

 Then tracing back through the larger vessels I found the same to 

 hold, generally, viz a tri-radiate order of branching. Under slight 

 pressure in the exact dorso-ventral direction the main vessels, i. e. 

 all that can be seen under such circumstances, preserve a tolerably 

 clear symmetry of arrangement and individuality in their lateral 

 positions. In the attempt to sufficiently compress the animal to 

 observe the terminal branchings we loose sight of this on account of 

 the shoving of one system above the other, in general too of one 

 system more posterior than the other, and the bringing of portions 

 of both into the same field of view. 



VoELTZKOw seems to agree pretty closely with Huxley's observ- 

 ations, made in 185G, and regards the systems of the two sides as 



