208 DONALD WALTON DAVIS 



siphonoglyphs, directive mesenteries, and orange stripes. An 

 orange stripe is invariably found opposite the siphonoglyph be- 

 tween the Hnes of attachment of the members of the pair of 

 directive mesenteries. As Davenport has stated, the orange 

 stripes occur only in endocoels. Comparison of the number 

 and position of the orange stripes as seen in the living animal, 

 with the number and position of the mesenteries as found in 

 sections, indicates that the orange stripes he between the mem- 

 bers of pairs of complete mesenteries, and also, contrary to the 

 statement of Davenport, of incomplete mesenteries of the 

 highest grade. For instance, the specimen a section of which is 

 represented by figure 17 showed ten orange stripes; those repre- 

 sented by figures 19, 21, 22, and 26 showed twelve stripes each. 

 In a regenerating specimen in which all the mesenteries and stripes 

 of the new region are formed, the above statement holds (with 

 rare exceptions to be mentioned later) for both new and old 

 parts. 



The frequency with which division occurs in the endocoels 

 occupied by orange stripes suggests the possibility that these 

 stripes have some functional significance in the processes of 

 fission or regeneration. It is clear, however, that the presence 

 of such stripes is not essential to the normal progress of these 

 processes. Specimens divide spontaneously in other regions, 

 and the resulting pieces, as well as similar fragments artificially 

 produced, regenerate readily. Furthermore, the related species, 

 S. davisi, reproduces freely by the same method, yet is destitute 

 of any such stripes. 



Davenport ('03, p. 143) calls attention to the fact that the 

 cinclides occur on the stripes. I find, however, that they are 

 not confined to the orange stripes. Figures 33 and 34 show 

 three cinclides, clearly marked by protruding acontia, none of 

 which are in positions occupied by orange stripes. In figure 19 

 at X appears another cinclis, likewise not situated on an orange 

 stripe. Under favorable conditions of lighting, the cinclides are 

 readily visible on the living specimen with the aid of a hand lens, 

 and their distribution may be accurately determined. They are 

 found in vertical rows in all positions in which fission planes may 



