142 THE APODOUS HOLOTHURIANS 



The anchors (Plates X, fig. 8; XII, fig. 5) occur only iu the genus Molpadia, in 

 some species of which they occur throughout life, while in others they are pres- 

 ent only in youth, and in still others they are apparently never present. They 

 were formerly supposed to be chai'acteristic of a genus " Ankyi'oderma. " They 

 differ essentially from the anchors of the Synaptidnp, and their presence has 

 no bearing whatever on the question of the relationship of that family with the 

 Molpadiida^. Although in a few species anchors are present in connection with 

 a single perforated plate, in most species where they occur at all they are asso- 

 ciated with a rosette of racquet-shaped, perforated plates, the number of which 

 varies from three to eight in each rosette. The anchors lie at nearly right 

 angles to the plates, though they are of course capable of movement, and ordi- 

 narily they stand out evidently from the body-surface. The attached end is 

 never flattened and branched or serrate, as in the Synaptida?, but is enlarged 

 and circular in outline and perforated with several holes, the number and ar- 

 rangement of which is quite variable. The free end of the anchor is provided 

 with two (rarely three or four) arms, which are coarsely serrate with from two 

 to six teeth. Commonly the anchors are liroken off by the rough treatment the 

 animal receives in a dredge or trawl, and the basal parts are then likely to be 

 mistaken for peculiar cups or tables. 



Besides the various sorts of calcareous bodies just described, the con- 

 nective tissue of Molpadids often contains peculiar spheroidal, ovoidal. or 

 ellipsoidal l)odies, 10-100 /t, more or less, in diameter, of a character- 

 istic yellow, brown, or red color (Plate XI, fig. 14). The color varies 

 greatly in different individuals, but is apparently lightest in youth and 

 darkest in old age. It first appears as a pale brownish-yellow shade, be- 

 comes more and more abundant. For many years the chemical nature of these 

 deposits was unknown and they have commonly been called the "colored 

 bodies," "red bodies," "wine-red bodies," or "colored calcareous bodies;" but 

 as there was reason to think they were not calcareous, the latter name has been 

 little used. These bodies first appear as mere spherical granules, but increase 

 in size by the continued deposit of similar material in concentric layers, and 

 this concentric structure is usually obvious. Oftentimes two, or even three, of 

 these granules become enclosed ultimately iu a common layer, so that the 

 colored body seems to have been formed around two (or three) centers simul- 

 taneously. One of the remarkable things about these deposits is that they may 

 be formed through the change of calcareous particles. (See Plate XII, figs. 

 10-12.) Various writers (Theel, '86a; Ludwig, '94; Koehler and Vaney, :05, 

 et al.) have noted the gradual coloring of a calcareous deposit and its ultimate 

 disappearance into small groups of "colored bodies." There is no doubt that 

 the number of "colored bodies" increases with the age of the individual, and 

 there is good reason to believe that in many cases at least such increase is ac- 



