THE STRUCTURE AND AFFINITIES OF HERDMANIA CLAVIFORMIS. 257 



Herdmania and its nearest relatives is its possession of two distinct epicardiac 

 tubes. As pointed out in the description, in this character it is wholly unique among 

 ascidians. This count alone would certainly securely establish the family rank of the 

 genus. It shows as conclusively as morphological evidence can that the evolution 

 of the species has been on an independent course for a long way. But the condition 

 of the fused tubes in Fragaroides, particularly the short separation of their posterior 



Polyclinid branch. 

 (Synoicum, Fragarium 

 Amarouciuin, Polyclinum, et<3.) 



Herdmania. 



Clarelinid branch. 

 (Rhopalaea, Ecteinasculia, 

 Purophora, Clavelina, etc.) 



Distomid branch. 



(Diazona, Distoma, 



Distaplia, Colella, etc.) 



Ascidia-like 

 Ancestor. 



FIG. A. 



ends and the relation of these to the pericardium and heart, shows as positively, it seems 

 to me, that the two forms had a common ancestor not greatly remote ; that is, less 

 remote than the common ancestor from which this ancestor and the clavelinid stock 

 arose. Numerous other characters of varying but subsidiary value likewise testify 

 to the nearer relationship of Herdmania to the Polyclinidse. The most important 

 of these, in the order of their importance, are: the position of the genital glands, 



