354 



OILMAN A. DREW. 



of the cilia become the free margins of the inner palps. 

 The two inner palps are continuous posterior to the mouth_, 

 where they form a slight ridge (figs. 55 and 63). Like 

 the elevation anterior to the mouth, this never becomes 

 prominent. 



The inner surface of each outer palp becomes folded near 

 its anterior end to form ridges and grooves (fig. 55), and the 

 postero-ventral portion protrudes to form a lobe. This lobe 

 is the beginning of the formation of the palp appendage. 

 The edges of this lobe soon begin to thicken, and a groove 

 is left between the ridges thus formed. This is accompanied 

 by a considerable growth in length (fig. 56, pap.). At this 

 stage of development the palp appendage is seen to corre- 

 spond to two of the ridges on the general surface of the palp, 

 with a groove enclosed between them. 



Posterior and dorsal to this appendage another smaller 

 appendage is formed (fig. 56). This is also on the outer palp, 

 and consists of two ridges with a groove between them. It 

 never grows to be very long, but resembles the large appen- 

 dage that lies ventral to it in its formation. 



As development proceeds the larger appendage (fig. 56, 

 pap.) twists, so that ifcs groove opens dorsally and posteriorly 

 (fig. 57, pap.), and the smaller appendage twists so that its 

 groove opens ventrally. This double twisting brings that 

 portion of the small appendage that was dorsal nearly or 

 quite in contact with that portion of the large appendage 

 that was ventral, so that for a short distance the two grooves 

 together form a tube that opens anteriorly between the two 

 palps (fig. 57). During the development of the palp appen- 

 dages both outer and inner palps have grown to be quite 

 large, and their ciliated surfaces have been thrown into 

 series of ridges and grooves. 



The palps on each side of an adult animal consist of two 

 large, somewhat triangular folds of tissue (fig. 48, Ip.), united 

 to each other along their dorsal margins, and suspended 

 from the body-wall by a thin membrane. The outer palps 

 on the two sides of the body are connected in front of the 



