Fissiparous Species of Tubicolar Annelid. 123 



visceral cavity, attached only by a few delicate threads of con- 

 nective tissue, to the parietes. It is most curious to watch the 

 regular contractions of these pendent vessels, their momentary 

 emptying, and their subsequent distention and erection by the 

 returning wave of fluid. And in considering the nature of 

 this remarkable system of vessels, it is most important to note 

 that we have here, at any rate, no circulation, but a mere 

 backward and forward undulation.* 



Ciliated Canal. — A clear, longitudinal, very narrow ( T1 Vo to 

 ■gshu inch) canal (fig. 6, a) may be observed extending along 

 the ventral surface of the intestine in the middle line, from the 

 anus, where it appeared to me to open, as far as the brown di- 

 lated stomach, when it either stopped or became so obscured as 

 to be no further traceable. The canal had well-marked walls 

 with a double contour, which sometimes appeared curiously 

 broken ; and contained, set along its dorsal wall, one to four 

 longitudinal series of cilia (fig. 9). These were placed at regu- 

 lar intervals, and worked together, as if they were pulled by 

 a common string. In young specimens there was only one 

 cilium in each row, but in the older ones I saw as many as four 

 in each transverse line. Has this enigmatical canal anything 

 to do with the * typhlosole' of the earthworm % 



On the dorsal surface of the head a longitudinal canal, 

 which sometimes appears to be ciliated, was visible at b 

 (fig. 3) ; posteriorly it divided into two branches which dilated 

 into granular caeca, arranged in a kind of festoon in the first 

 segment of the thorax. 



The coloration of this part of the body prevented me from 

 determining whether this canal opened externally or into the 

 oesophagus, and also whether it was in any way connected 

 with the ventral ciliated canal, — both of them points of much 

 interest. 



However this may be, these sacs are clearly homologous 

 with the curious sacs which have been described in Chlorcema, 

 and perhaps with the sacs opening externally, which are found 

 in the anterior segment of Pectinaria. 



* The general contractility of the vessels of the annelids has already been 

 pointed out by De Quatrefages. Siebold doubts the existence of a regular cir 

 culation in the majority of the Annelida. Op. cit., p. 210. 



