294 SYNOPTIC COLLECTION. 



most varied situations, and their organs have passed 

 through such a complete change that they are of no phy- 

 logenetic value. 



Aphrodite or the "sea-mouse" (No. 729) belongs to 

 the first group. It is unique in possessing an almost in- 

 numerable number of delicate hairs and larger setae, 

 which reflect the most brilliant prismatic hues, making 

 the worm a marvel of beauty. Alcohol has no power to 

 rob this animal of its gorgeous tints. The mechanical 

 cause for the coloring lies in the extremely fine lines on 

 the surface of the hairs which break the light into its 

 component elements, but the reason for the file-like sur- 

 face and the " forest of prisms " is not so clear, especially 

 as it is said that these worms are usually covered with 

 clay so that their beauty is hidden from the sight of other 

 animals. 



No. 730 is a preparation of Aphrodite showing the 

 scale-like respiratory organs. These are situated on the 

 back of the worm and are protected by a felting of hair 

 (see No. 729). The water passes through the felting 

 and bathes the scales, after which it is expelled from the 

 posterior end. 



A relative of Aphrodite is found in the scale-bearer 

 Phyllodoce (PI. 731, P, maculata Oersted). The young 

 larva (fig. i ; fig. 2, side view of the same) has a band of 

 cilia and the body is segmented. Gradually the worm 

 lengthens (fig. 3 ; fig. 4, ventral view of same), the pad- 

 dles become distinct and also the setae, though the cilia 

 still persist. The tentacles grow out and the large mouth 

 (fig. 4) is back of the band of cilia. The body continues 

 to grow longer (fig. 5) . The head now possesses eight 

 tentacles, as in the adult (fig. 6). 



Sigalion squamatum (No. 732) is also provided with 

 scales on many of the segments. This is such a peculiar- 

 looking worm that at first sight it seems as though the 

 body wall had been removed exposing the internal organs 

 and that these consisted of a long, double, vertebral rod 



