162 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



ians (Proto-ascidiacea) to have been, and (2) because this 

 group occupies one of several points of contact between 

 the Ascidiae Simplices and Ascidise Compositse, Bhopalcea 

 linking on in the one direction to Giona and the Ascidiidse, 

 while Glavelina and Ecteinascidia pass in the other 

 direction into Diazona* Chondrostachys and the Dis- 

 tomidse. For a further discussion of these phylogenetic 

 relationships I may refer to the last part of the " Chal- 

 lenger " report on the Tunicata.t 



EXPLANATION OF THE PLATES. 



Reference Letters. 

 a. anus; at. atrial aperture; br. branchial aperture; 

 b.v. blood vessel ; c.d. connecting duct ; c.d'. same in a 

 rudimentary condition; d.l. dorsal lamina; d.t. dorsal 

 tubercle; gl. digestive gland ; h. m. horizontal membrane; 

 i. intestine; I. languet ; m.b. muscle bands; i.l. internal 

 longitudinal bars ; ce. oesophagus; ov. ovary; sg. stigmata; 

 st. stomach ; r. rectum ; o.d. oviduct ; si. stolon ; £. testis; 

 tn. tn'. tentacles; v.d. vas deferens; tr. tranverse vessels. 



* In fact Diaznna, comes so close to Ecteinascidia and Rhopalcea that I 

 would have no great objection to place it beside them in the family Clavel- 

 inidfe. It seems to me to be a form as nearly as possible exactly intermediate 

 between Distomidre and Clavelinidfe, and consequently very difficult to place 

 in a serial or tabular classification through presenting no difficulty in a 

 phylogenetic arrangement. 



tZool. Chall. Exp., Part LXXVI, 1888, p. 121. 



