INTESTINAL RESPIRATION IN ANNELIDS. 757 



Aulophorus tonkinensis (Vejd.). 



Tlie vascular system has been bricHy described by me in a previous paper (49) ; it 

 closely resembles that of Dero. 



The antiperistaltic contractions of the alimentary canal were, in the posterior 

 portion of one specimen examined, mainly confined to the portion of the wall containing 

 the dorsal vessel ; the opposite side of the intestine moved but little, i.e. the pheno- 

 menon manifested itself in this region principally as a postero-anterior contraction 

 of the dorsal vessel. In the middle of the body, however, in segments xiii., xii., and xi., 

 the whole circumference of the alimentary canal manifested a series of very violent 

 antiperistaltic contractions, jjatcr, it was observed that the slowly moving antiperi- 

 staltic pulsation, which embraced the whole intestinal wall, became transformed in 

 segment xi. into an extremely rapid wave, which, affecting the dorsal vessel only, shot 

 forwards through the rest of the field of the microscope almost instantaneously. 



Thus in Aulophorus tonJiinensis the same series of contractions may manifest itself 

 at one place as an antiperistalsis of the whole gut, and at another place mainly as a 

 contraction of the dorsal vessel. It may be remarked that the latter part of the 

 observation detailed above is strongly reminiscent of the condition in the Enchytraeidse. 



Slavina punjabensis Stephenson. 



I have no detailed observations concerning the anatomy of the vascular system in 

 this form. The opacity of the specimens, due to the adherent foreign particles, renders 

 an examination of the details difficult or impossible. The dorsal vessel appears as a 

 part of the wall of the intestine ; and the ventral vessel is separated from the 

 intestine, as in other Naididse. 



Relation of Contractions of Vascular System to those of the Alimentary Canal. — 

 As in Dero and Aulopliorus, the dorsal vessel in this form is never, so far as I have seen, 

 independently contractile, apart from the rhythm of the gut contractions. The follow- 

 ing observations will illustrate the nature of the relations between the two : — 



(1) In a specimen which was preparing to divide, with eyes alread\- forming in its 

 posterior half, an ordinary typical antiperistalsis at the rate of twenty-five per minute 

 was observed in the hinder part of the anterior animal of the chain ; the dorsal vessel, 

 as forming part of the intestinal wall, shared in the constrictions, and was emptied in 

 a forward direction simultaneously with the pa.ssage of the waves. Further back, in 

 the middle of the posterior animal, the phenomenon manifested itself mainly as a strong 

 and swift contraction of the dorsal vessel ; the ventral side of the intestine, however, 

 was slightly indented as each contraction passed along. Further back still, near the 

 hinder end of the posterior animal, the intestine took no share in the movement ; the 

 ventral wall showed no indentation on the passage of the contractile wave, which was 

 confined to the dorsal vessel. We have, then, in such a case as this, a single contractile 



