NOTES ON ACTINOTEOCHA. 481 



the lumen of tlie stomacli and extending along the sides 

 from beyond the opening of the oesophagus to near the 

 posterior end. The cells along the dorsal median line of the 

 stomach, and the cells of the posterior part of the stomach 

 just before it opens into the intestine, have elongated nuclei 

 placed vertically, and resemble the oesophageal cells. There 

 .does not appear to be any reason for regarding the diverti- 

 culum as anything but a part of the stomach. The stomach 

 could grow forwards only ventrally to the oesophagus, and 

 when the front end of this outgrowth meets the oesophagus, 

 which bends down to the mouth, it is obliged to grow past it 

 along its sides. The form and the position of the diverticulum 

 can thus be explained on mechanical grounds. Whether the 

 diverticulum has any special function ; whether, for instance, 

 its association with the large mass of blood-corpuscles is 

 purely an accident, I cannot say. 



(4) The Subneural Gland. — This structure has given 

 rise to a good amount of discussion. According to Masterman 

 it ai'ises as an ectodermal invagination in front of the mouth. 

 I have not seen this stage. In the earliest stage of the organ, 

 that I have observed, it is present as a shallow diverticulum 

 of the dorsal wall of the " oesophagus," which projects some- 

 what backwards into the collar cavity, just behind the 

 mesentery between the preoral and collar cavities. In the 

 latest stage I have seen the gland opens by a wide aperture 

 just within the mouth, and is directed forwards into the pre- 

 oral lobe, in which it lies between the ectoderm of the lower 

 wall and the cavity of the lobe, and is separated from this 

 cavity by the basement tissue and scattered nuclei which line 

 the preoral cavity. If I interpret these facts correctly, the 

 organ first appears in connection with the collar, and during 

 development shifts forwards into the preoral lobe ; and this 

 is in harmony with the development of the " Eicheldarm" of 

 Balanoglossus. In Balanoglossus, the " Eicheldarm " during 

 development is described as lying in a space between this 

 ventral wall and the cavity of the preoral lobe ; and it is 

 certainly a remarkable coincidence between this arrangement 



