COMMON SPOON-WORM. 2 65 



of an internal blood-vessel to the aims, which is placed at 

 the posterior extremity, and surrounded by two circles of 

 ten similar but shorter bristles. The skin near the vent is 

 longitudinally striated. 



On dissection we find a long and winding intestine of a 

 brownish hue. There is a dorsal vessel running the length 

 of the animal, containing red blood, the globules of which 

 are large and irregular in form. The bristles near the head 

 are retracted by powerful muscles. Near them open four 

 genital sacs, two on each side. In these were detected 

 spermatic animalcules. These sacs are transparent, and 

 tipped with orange. On each side of the anus are two 

 tubular sacs, each about three-fourths of an inch in length. 

 These are the organs of respiration. When a portion of 

 one of them is placed under the microscope alive in sea- 

 water, a most beautiful organization is presented. They 

 are seen to be studded with cup-shaped bodies, like polypes 

 in form, round the margin of each of which is a circle of 

 vibratory cilia, so large that they may be easily seen with 

 a common lens of three-fourths of an inch focus. On the 

 internal surface of the respiratory sacs instead of cups there 

 are little tubercles corresponding to the cups, and covered 

 like them with vibratile cilia, the whole forming one of the 

 most beautiful arrangements of those singular organs seen in 

 the animal kingdom. This arrangement has, as far as I 

 am aware, not been noticed hitherto. It is represented in 

 the vignette. 



The Spoon- worms were continually changing form, filling 

 themselves with water, perhaps through the medium of the 

 respiratory tubes. When supplied with fresh water they 

 would swim in a revolving manner like a worm with great 

 vivacity, and afterwards rest at the bottom of the vessel 

 and swell themselves out. 



