BUDDING IN TUNIC AT A. 63 



reference should be made to the works of Delia Valle — it 

 may be remarked that the budding of the Didemnidae and 

 Diplosomidae presents features which render it probably the 

 most primitive of all the types found in the Tunicata. 



Type 1. CEsophageo-atrial. — Endoderm of bud derived 

 both from the oesophagus and atrium (peribranchial cavity) 

 of parent. Didemnidae, Diplosomidae. 



Type 2. Atrial. — Endoderm of bud derived from atrium 

 of parent. Buds lateral and paired, e.g., Botryllidae, 

 Polystyelidae. 



Type 3. P /laryngeal. — Endoderm of bud derived by 

 means of tubular (epicardial) diverticula from the pharynx 

 of parent. Buds unpaired, median. 



(i.) Epicardial tubes paired, not united, but only one 



functional, e.g., ventral bud of larval Distaplia. 

 (ii.) Epicardial tubes sooner or later united distally to 

 form an unpaired tube. 

 (a) Independent in parent, but uniting secondarily in 



bud, e.g., Doliolum. 

 (d) Uniting in parent, but retaining the double com- 

 munication with pharynx, e.g., Clavelina, 

 Distomidae, Polyclinidae, Perophora (?). 

 (iii.) Epicardial tubes no longer paired, but developed 

 from the first as a single median posterior prolon- 

 gation of endostyle, e.g., Pyrosomidce, Salpidce. 

 It is interesting to compare the above classification, 

 which is founded upon structural characters, with one based 

 on the position of the buds - with regard to the parent. It 

 will at once be seen that the two schemes correspond very 

 closely with each other, and as the second scheme may not 

 be without some usefulness, I give it below. 



Group 1. Buds lateral, on one side only. Didemnidae, 

 Diplosomidae. 



Group 2. Buds lateral, on one side of larva, but on both 

 sides of buds. Botryllidae, Polystyelidae. 



Group 3. Buds ventro-lateral, but only formed on one 

 side. Larval Distaplia. 



Group 4. Buds median and ventral. Thaliacea. 

 (i.) Minute. Doliolidae. 



