No. 3-] STUDY OF STENOSTOMA LEUCOPS O. SCHM. 293 



pits ; 3, by a migration outward of some of the epithelial cells to 

 form a second outer layer. On page 265 it has been stated that 

 the nuclei of the epithelial cells divide by karyokinesis. If a 

 new layer of cells were formed by the first method, we ought cer- 

 tainly to find numerous spindles vertical to the surface in every 

 developing pit. No such spindles have been seen. In studying 

 the development of the ganglia which surround the pits with re- 

 gard to the second point, I have been unable to find any evidence 

 of the addition to the wall of the pit of a layer of cells derived 

 from the ganglia. The muscular layer always intervenes be- 

 tween the ganglion and the cells of the pit. With regard to the 

 third point, we have no evidence that some of the cells do or 

 do not migrate to form a second cell layer. In macerations I 

 have been able to get nothing more than the ciliated epithelial 

 cells. 



Dish- Shaped Organs. 



The dish-shaped organs are located near the dorsal surface of 

 the body, on either side of the mouth, and just beneath the in- 

 tegument. They are surrounded and supported by the paren- 

 chyme. These organs have the form of a saucer. They are 

 10 yu, in diameter. When a quiescent worm is observed from 

 the dorsal side, the dish-shaped organs are seen from the side. 

 In this view they have a crescentic appearance (Fig. i, D.O.). 

 The concave surface of the dish is thus directed forward. 

 When the body is contracted, these organs are so turned that 

 the concave surface faces dorsalward, so that when a contracted 

 worm is observed from a dorsal view the organs appear circular. 



In the living worm they appear to be made up of a single 

 layer of from fifteen to twenty spherical or ovoid, highly refrac- 

 tive bodies. These bodies average 2.5 /i in diameter. By very 

 careful focusing they may be seen to be connected with the 

 posterior ends of the lobes of the brain by a very small nerve. 

 These nerves are more plainly seen in the newly formed worms 

 of a chain. 



In a section which was parallel with the surface of these 

 organs they appear to be made up of a single layer of round or 

 ovoid bodies which are very coarsely granular (Fig. 25). These 

 bodies take a very dark stain with hasmatoxylin even though 

 the rest of the section is but shghtly stained. In this they 



