560 T. H. Morgan and N. M. Stevens. 



fully for the reasons given above, v^e think, hov^^ever, that our new 

 work is of more interest in connection with the problems of 

 polarity and heteromorphosis in Tubularia. 



The work was carried out during the summer of 1904, while 

 enjoying the hospitality of the Hopkins Marine Laboratory of 

 Leland Stanford Junior University. The species of Tubularia 

 that is found near Pacific Grove is T. manna. 



It differs in some respects from the forms found at Woods Hole 

 and at Naples, the principal difference being that it has a single 

 hydranth at the free end of an unbranched stem attached by 

 stolons to the rocks. In regard to its powers of regeneration, 

 it appears to be very similar to the other two forms, the main 

 difference being its stronger tendency to produce a stolon from an 

 aboral cut end rather than a heteromorphic hydranth. 



GENERAL ARGUMENTS THAT ARE OPPOSED TO THE SUPPOSED 



FUNCTION OF THE RED PIGMENT AS A FORMATIVE 



OR NUTRITIVE FACTOR. 



The discussion of the problem that follows may be made clearer, 

 if we review here the points that bear on the supposed function of 

 the red pigment as a formative or nutritive factor. 



First. The stem of Tubularia marina contains throughout its 

 length two ridges standing opposite to each other and nearly meet- 

 ing in the middle of the stem. These ridges are connected by 

 strands of endoderm at more or less irregular intervals, forming 

 a perforated partition between the two circulatory canals of the 

 stalk. The fluid in the central cavity of the stem moves up one 

 canal, across to the other side of the partition just below the 

 stomach of the polyp, and down the other canal. Long lash-like 

 flagella, belonging to the endoderm cells, keep the fluid in circu- 

 lation. Occasionally granules or food particles are contained in 

 the fluid, but ordinarily it is quite clear and its movement is 

 consequently difficult to demonstrate. 



When a piece of the stem is cut off, its ends close rapidly, and 

 the circulation continues as before. At first the fluid contains no 

 granules, or only an occasional one. The first changes, prepara- 



