48 HAROLD SELLERS CO I. To N. 



duct of the pyloric gland opens into the stomach and is derived 

 in development from the eiitoderm is a condition characterizing 

 no other excretory >ystem out side of the Arthopods. How- 

 ever, HIUV tin- vertebrate liver has been shown by C'hr/onsze- 

 /r\\-k\ '66) to excrete carmin, and has morphologically the 

 >.mu po-ition as has the pyloric gland of the ascidian and has a 

 Hinil.ir development, there is good reason to believe that the 

 t\\<> are homologous. \Yilley has homologized the organ with 

 the hepatic ca'cum of Amphioxus which Hammar ('93) about 

 the same time compared to the liver of the Craniota. Can we 

 not conceive that in the hypothetical ancestor of the vertebrate 

 the liver arose as an organ of excretion and in the tunicate it has 

 retained more of those characters ? 



SUMMARY. 



1. There are in Botryllns two sorts of terminations to the tubes 

 that compose the pyloric gland, bladder-like ampulla? and long 

 straight blind tubes the latter we have called rectal tubules 

 because in many cases they extend to the region of the rectum. 



2. The ducts and ampulla? of Botryllus as well as Ascidin. 

 Styela, Molgula, Perophora, Clavelina and Amaroecium are lined 

 by cells- bearing long w r hip-like flagella, the ends of which are 

 directed toward the mouth of the duct. 



3. Many of the rectal tubules have a termination difficult to 

 interpret. This has the appearance, in most cases, of a cup-like 

 depression in the end of the tube which seems to form a communi- 

 cation between the blood cavity and the lumen of the tube. In 

 no case, however, could such a communication be demonstrated. 



4. The direction in which the free ends of the flagella point 

 indicates that the contents of the lumen pass toward the stomach 

 and therefore the function of the organ is secretory rather than 

 that of absorption. 



5. Part of this secretion is probably found in the minute yellow 

 globules found in the cells of the ducts and ampulhu. It these 

 yellow globules represent a secretion, this is soluble in water 

 and does not form masses in the lumen of the tube as in Micro- 

 cosmus and Styela. 



6. Bismarck brown and neutral red are concentrated in the 



