PART III. 



THE SYNAPTID^L 

 Order PARACTINOPODA Ludwig. 



External appendages of water-vascular system arise from circular canal 

 and appear only as circumoral tentacles. While five of these are radial in posi- 

 tion, no true radial canals are present in adults. 



Family SYNAPTID^ Burmeister. 



More or less cylindrical elongated holothurians with terminal mouth, with- 

 out respiratory trees and with water-vascular system greatly reduced; cir- 

 cumoral tentacles, either simple, pinnate, or digitate, are present but lack am- 

 pulla) ; there are no pedicels or papillae; circular muscles of body-wall contin- 

 uous, i. e., not broken or interrupted at radii; characteristic, sense-organs 

 (positional organs) present, situated beside radial nerves, near nerve ring; 

 minute ciliated funnels, apparently having an excretory function, usually pres- 

 ent in body-cavity on or near mesenteries; calcareous deposits, in form of 

 anchors and plates, wheels or sigmoid bodies usually present, but no tables or 

 phosphatic deposits (see p. 142) occur. 



MORPHOLOGY. 



FORM AND SIZE. The body is generally elongated and more or less cylin- 

 drical, but the exact shape and proportions differ in different species, and, 

 owing to its remarkable contractility, its form differs greatly in the same indi- 

 vidual under varying conditions. The largest species in the family is Synapta 

 maculata, which reaches a length of more than 200 cm., though the diameter is 

 not commonly more than 3 cm. The smallest species is Leptosynapta minuta, 

 which is only 3 to 5 mm. long. Between these two extremes we find great di- 

 versity, but species more than 30 or less than 3 cm. when fully grown, are in- 

 frequent. 



COLOR. In color there is some variety, but really bright colors are rare; 

 white, flesh-color, dull yellowish, and gray are the more usual shades, but dull 

 shades of red are common. Protankyra rodea is said to be "carmine-red" and 

 Scoliodota japonica "blood- red." Green is" occasionally found in an olive, or 

 some other dull shade, but the bright shades are rare. Some species are very 

 dark-colored, and have been described as "crimson-black," "dark violet-black," 

 and "brown." The color is seldom uniform, but spots and little papillae 



42 



