128 JOHNS HOPKINS UNIVEESITY MOEPHOLOGICAL MONOGEAPHS. 



SECTION 3. Salpa and Doliolum. 



First, as regards the comparison between Salpa and Doliolum, are we 

 to believe with Uljanin that they are widely separated, or with Herdman 

 and Grobben that they are closely related ? 



To my mind there is no room for doubt. Unquestionably Doliolum, 

 Anchinia, and Salpa are more closely related to each other than they are 

 to any other Tunicate except Pyrosoma. 



I have already shown, page 9, that the contrast in the muscle bands 

 upon which the groups Cyclomyaria and Desmomyaria are based has no 

 existence. In all Doliolums some of the muscle bands are imperfect 

 rings ; in many species of Salpa the oral and atrial muscles are perfect 

 rings, and in the most common and best known species of Salpa, the 

 solitary Salpa democratica, most of the body muscles are as perfectly 

 closed dorsally and ventrally as the rings of Doliolum. Anchinia, at 

 least, is only by courtesy a Cyclomyarian, for it has no circular muscles 

 except the oral and atrial sphincters, as the figure of the sexual animal 

 given by Kowalevsky and Barrios (4), Plate III, Fig. 8, clearly shows. 



The groups Cyclomyaria and Desmomyaria are then purely artificial 

 and without scientific value. 



Uljanin lays stress upon the presence of a tailed larval stage in the 

 embryo of Doliolum and its absence in Salpa, but a comparison of the 

 Doliolum larva which he shows in his Plate Y, Fig. 1, and which I have 

 copied in my Plate VIII, Fig. 3, with the embryo of Salpa hexagona 

 which is shown in my Plate III, Fig. 4, will show that the eleoblast k of 

 the salpa embryo is a true tail, bearing exactly the same anatomical 

 relations to the body as the tail of the doliolum larva. In my account of 

 its minute structure, page 38, I have shown that sections prove it to be, 

 without question, a degenerating larval tail. 



Uljanin says that he regards Salpa as standing alone among the 

 Tunicates, and that its resemblance to Doliolum is superficial and due to 

 secondary adaptation, but he gives no valid reason for this opinion. He 

 says that the anomalous foetal development of Salpa, and the part which, 

 according to Salensky, the tissues of the mother-organism take in the 

 construction of the embryo, show that it is very different from all other 

 Tunicates and render it difficult to place in the system. I have shown 

 that the development of the salpa embryo, while very remarkable indeed, 

 is by no means totally anomalous, and while we know nothing of the 

 way its foetal mode of development and its placenta were acquired, they 



