OBSERVATIONS ON POLYZOA. 



107 



and goes to the evaginable endocyst on the dorsal side. 

 The range of individual variations in the principal branch- 

 es may be estimated from figm*es 9, 10 and 11, They 

 were taken from different zooids on one colony of Fred- 

 ericella regina collected at Gorham, Maine, figs. 9 and 

 10 being from the same zo5id. In fig. 11, the main loph- 

 ophoric trunk divides close to its base, in figs. 9 and 10 

 the division is somewhat higher, in fig. 11, also, the lower 

 part of the trunk is much more distinct from the epistomic 

 nerve than in fig. 10, where they run together in one com- 

 mon base. The polypidal branch of fig. 9 entered the 

 evaginable endocyst a very little above and to the left of the 

 anal orifice, while that of fig. 10 entered the same part but 

 a short distance from the lophophore. 



The anterior set of 

 nerve-branches are 

 six in number, three 

 on either side of the 

 nerve-mass. Their 

 bases sometimes coa- 

 lesce in one main 

 trunk on either side 

 as in fig. 1 1 , and they 

 may then be very 

 readily distinguished 

 but frequently it is a 

 matter of great difii- 

 culty to define even 

 the cesophagal , Avhich 

 is the one most gen- 

 erally visible (figs. 9, 10, T""). I was imable to follow 

 these branches further than to their points of contact with 

 the alimentary canal, the cesophagal branch to the oesopha- 

 gus, which it probably encompasses forming a true cesoph- 

 agal collar, the central, or Gastric branch, to the upper 

 part of the stomach, and the dorsal, or Intestinal-branch, 

 to the intestine. They undoubtedly supply the walls of 

 these organs with nervous filaments, but these were too 

 minute to be definable among the more highly colored cells 

 of the alimentary canal. 



Fig. 10. Fig. 11. Fig. 12. 



Figs. 9 and 10, nerve-mass of Fkederi- 

 CELLA REGFNA from the same zooid, viewed 

 dorsally and laterally. Fig. 11, lateral 

 view of nerve-mass from another zooid of 

 the same colony. Fig. 12, dorsal view of 

 nerve-mass of Pltoiatell.v diffusa. T', 

 Epistomic nerve-trunk. T", Brachial 

 nerve-branch. T'", Polypidal nerve- 

 branch. T"", G^sophagal nerve-branch. 

 T, Gastric nerve-branch. T, Intestinal 

 nerve-branch. U, The Brachial and Oral 

 branches of the Lophophoric nerve- 

 branch. 



