258 THE STRUCTURE AND AFFINITIES OF HERDMANIA CLAVIFORMIS. 



the structure of the stomach wall, and the presence of lobes on the siphons. The 

 large number of branchial tentacles, the yolklessness of the eggs, and the traces 

 of tubular or alveolar structure of the neural gland are all features that take the 

 ancestral line far back toward the simple ascidians. The uterine function of the 

 oviduct, the peculiar breaking up into groups of the branchial tentacles, and the 

 inequality of the lobes of the branchial siphon show finally that the evolutionary 

 way has been a lone one, for a considerable distance. 



Phylogenetic trees are out of vogue just now with fashionable zoologists. Never- 

 theless I venture to believe that well-constructed ones always have had, and will ever 

 continue to have, real scientific value. We can make out here with a good deal of 

 confidence not a whole tree, indeed, but only a small branch with a few of its branch- 

 lets. The course of things that has produced the merosomatous ascidians, using this 

 term in Herdman's restricted sense, through the " social " phases may be represented 

 by Figure A, page 257. I try to represent here three things: (1) relationships; (2) 

 degree of divergence from ancestral stock; and (3) degree of specialization. 



VII. BIBLIOGRAPHY. 



Caullery, M. 



'95. Contributions a I'e'tude des ascidies composes. Bull. sci. France et Belg., torn. 27, pp. 1-158, pi. 1-7. 



Caullery, M. 



:00. Sur des Clavelines nouvelles (Synclavelina n. g.) constituant des cormes d'ascidies compose'es. C. 

 R. Acad. Sci., Paris, torn. 130, pp. 1418-1420. 



Garstang, W. 



'91. Report on the Tunicata of Plymouth. Part I. Clavelinidae, Perophoridse, Diazonidse. Jour. Mar. 

 Biol. Assoc., new ser., vol. 2, no. 1, pp. 47-67, pi. 2. 



Garstang, W. 



'95. Budding in Tunicata. Sci. Progress, vol. 3, no. 13, pp. 43-67. 

 Gottschaldt, R. 



'94. Die Synascidien der Bremer Expedition nach Spitzbergen in Jahre 1889. Jena. Zeitschr., Bd. 28, 

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Herdman, W. A. 



'91. On the Genus Ecteinascidia, and its Relations, with Descriptions of Two New Species, and a Classifi- 

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 pis. 6-7. 



Herdman, W. A. 



'99. Descriptive Catalogue of the Tunicata in the Australian Museum, Sydney, N. S. W. Australian Museum 

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Hjort, J. 



'96. Germ-layer Studies based upon the development of Ascidians. The Norwegian North- Atlantic 

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