PLANKTON FROM NE\Y BRUNSWICK. 



291 



rapid transformation, it happened whilst I was not looking. 

 Brown-colouied debris appeared in the intestine ; and the 

 definitive PAor o?i?s-tentacles were without pigment. 



A conspicuous blood-vessel with red corpuscles traversed 

 the length of the body of the young Phoronis, transmitting 

 branches into the tentacles. 



The aboral extremity of the body was very mobile, adhering 

 with active, metabolic movements to the glass. Retractile, 

 digitiform, vascular processes, termed caecal capillaries, were 

 pushed out in rapid succession from 'the main vessel into the 

 mobile foot-disc and were withdrawn again at frequent intervals 

 (text-fig. 55). I am not aware that the retractility of these 

 first-formed aboral ceecal capillaries has been noted previously. 



Text-fig. 55. 



Posterior end of a young Flioronis immediately after the metamorphosis, showing 

 the retractile vascular processes in the mobile and adhesive foot. 



The above-mentioned foot-disc corresponds with the terminal 

 portion only of the ampulla of the fully-formed Fhoi-onis. The 

 csecal capillaries of the ampulla are figured by Selys-Longchamps 

 in a young individual of Phoronis sahatieri (see his pi. viii. 

 fig. 13). This author describes, on p. 35 of his monograph, the 

 special and independent contractility of the terminal portion of 

 the ampulla. The peculiar mobility of this part is associated 

 with a situs inversus of the muscular layers, the longitudinal 



