1909] Ritter: Halocynthia johnsoni a. sp. 71 



1/ (to the right in the figure) are recognizable on the particu- 

 lar // specified by the lettering, and these two generations can 

 readily be seen on must of the other 6's. In several instances 

 g " is also recognizable on b\ as, for example, on the fourth 

 from the base to the right. Furthermore g and g" may be rec- 

 ognized in several places on 6", for example on b" of b' a1 the 

 base to the left. 



lint the orderliness of branch production recognizable l" 

 cursory inspection extends still further. Figure 13 illustrates 

 especially well the points now to be noted. Although this figure 

 is diagramatic in a way, it is accurate as to numbers of branches. 

 The positions, too, of all the branches and length of the primar- 

 ies were determined by micrometer measurements, and the sec- 

 ondaries were drawn as accurately as possible. From this figure 

 it. is seen thai the branches />' of the first generation arc longesl 

 at a poinl on a somewhal distal to its middle, and that from 

 these of maximum length the others become gradually shorter 

 toward both the base and the apex of a. This undoubtedly 

 means that new branches of this generation are added both dis- 

 tally and proximately 1 from the initial ones of the generation. 

 A glance at any whole, full-grown tentacle reveals the general 

 form scheme as unmistakably as dues this young one. The spec- 

 imen from which figure 11 was drawn, for example, shews it 

 beautifully, but it was impracticable to draw the whole on a 

 scale large enough t<i bring out the smaller details the illustra- 

 tion nf which seemed of more importance. Again, inspection 

 of the branches b' shows that the secondary branches b", with- 

 out much doubt, follow in general the same scheme. Attention 

 to the disposition of the &"s of figure 11 shows thai the same 

 rule holds in this presumably full-grown tentacle. At any rate, 

 this much is obvious, that the largest b"s are never at either 

 end of the axes of the &'s. When it comes to the b' "s, the prev- 

 alence of the rule is not so obvious, though in many instances 

 intimations of it are seen. Attention should he called to the 



i Although allowing this statement to stand, I am now in considerable 

 doubt about the addition of new brandies proximalward. From observa- 

 tions made and information obtained touching somewhat similar series in 

 other organisms, it seems not unlikely that new additions are here always 

 distahvard from these already existing. 



