686 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



These are manifestly tactile organs and assist in placing the eggs 

 during Qgg la^dng. They are never found on males. 



The abdomen has no appendages nor any trace of theni at any stage 

 in its development. 



The digestive systent. — The mouth parts consist of two separate 

 organs united at their bases. The anterior portion has been called, 

 respectively, a "sting," a "gadd," and a "sucker" b}^ various authors. 

 The tirst of these names is the most applicable. This sting is a long, 



very sharp-pointed spine, tipped with 

 chitin and inclosed in a sheath of the 

 same material, to which it is so at- 

 tached that it can be extended and 

 withdrawn like the finger of a glove. 

 When not in use, it is partly with- 

 drawn and lies in a longitudinal 

 groove which runs forward between 

 the bases of the antennae. It is a 

 veritable sting, for the spine is hollow 

 and its lumen serves as the duct of a 

 poison gland situated at the base of 

 the sheath. 



The inner portion of the sting is 

 oe.m. soft and flexible and is folded upon 



itself when withdrawn. It is forked 

 near the base of the sheath and a 

 branch of the duct passes out to the 

 poison gland on either side (fig. 16). 

 When wished for use, the sting is 

 dropped down from its groove upon 

 the fish's skin, into which it is then 

 pushed by e version. 



Thus in the way in which it is 

 carried and used the sting bears con- 

 siderable resemblance to the proboscis 

 in certain hemiptera. Its chief use 

 appears to be that of puncturing the 

 skin and securing a strong flow of 

 blood both by its wound and also the irritation caused b}^ the pouring 

 in of the secretion from the gland. 



The posterior portion of the mouth apparatus is the proboscis; it 

 also is cylindrical and can be elevated or depressed at pleasure. But 

 it is much larger in diameter than the sting and is somewhat club- 

 shaped at the free end. When not in use, there is a groove extending 

 back between the bases of the two pairs of maxillipeds in which it is 

 carried. 



& — 



c h.r. 



Fig. 16.— Sting and poison gland of Ar- 

 GULUs versicolor, ch. r., Chitin rib ok 

 proboscis; (/., poison gland; (L, duct of 

 poison gland; mm., mandible muscles; 

 oe. TO., (ESOPHAGUS MU.SCLE; oe. m'., side 

 muscle OF (ESOPHAGUS; r.m., retractor 

 muscle; .1., sting. 



