51 G PToward Edwin Enders. 



older specimens, I have seen the "holdfast" extended till it resembled 

 a slender cord nearly as long as the body of the larva. At other 

 times it was contracted to form a thick papilla that was marked 

 with circular wrinkles that suggest annulation, as is shown in a 

 paper by Fewkes.^ The hold-fast is indifferently extended or con- 

 tracted when the animal swims about in the water. It still serves 

 as a prop by means of w^hich the larva may push itself forwards on 

 the bottom of the dish. 



When the animal swims rapidly through the water the portion 

 of the body posterior to the ciliated rings is contracted and flexed 

 dorsaiwards till the anus rests directly back of the third ciliated 

 ring. The body is then somewhat pear-shaped and the i-ings of pow- 

 erful cilia are around the thicker posterior portions. (See Text-figure 



D of Spiochsetopterus. ) This position of the cilia causes the animal 

 to swim in a wide cork-screw-like path. 



Tentacles. — The tentacles appear as a small papilla on each side 

 dorsal to the lateral angles of the mouth and posterior from the lat- 

 eral eye-spots. In this stage they are covered with fine cilia. 



Alimentary canal. — The alimentary canal is shifted forwards and 

 backwards by the muscular contraction of the body, nevertheless it 

 has undergone a considerable permanent change in position. 



The esophagus has become a narrow^, glandular tube with mus- 

 cular walls. Anteriorly it opens into the wide, funnel-like mouth, 

 then extends into the median plane of the body to the dorsal wall 

 of the stomach, with which it communicates about the level of the 



^The "hold-fast" is also shown by figures in papers by Claparede and Metcz- 

 nikow, M. Miiller, .Toh. Miiller, Beranec, and Wm. Busch. 



