44 



HAROLD SELLERS COLTOX. 



DISCUSSION. 



Turning now to the character of the pyloric gland in other 

 tunicates, we may as well begin with the Larvacse. Although 

 this organ is absent in most of the genera, it seems to be repre- 

 sented at least in a rudimentary form in two described by Chun 

 ('81) from deep water of the Mediterranean Sea Stegasoma and 

 Megalocerciis. Here we have a diverticulum of the gut which 

 may be a possible homologue of the pyloric gland or at least to- 

 the pyloric caecum. However, in no case is the organ developed 

 as it is in the other orders of tunicates. 



Our present knowledge of the pyloric gland in the Thaliacea 

 and Ascidiacea can best be presented in tabular form. The table 

 in question does not pretend to be complete but gives in con- 

 densed form the observations of various investigators. 



As far as thi*. di^.m h.i^ been particularly dr^i nbrd it is much 

 the same in all families. The usual number of the ducts is one, 

 but there may be more. The tubules are eilher dendriiir or 



