444 
Proceedings of the Royal Society 
3. On the Phytogeny of the Tnnicata. By W. A. Herdman, 
D.Sc., E.L.S., Professor of Natural History in University 
College, Liverpool. 
{Abstract.) 
This paper deals with the relationships between the different groups 
of Tunicata, and the attempt is made to trace their phytogeny, and 
to construct a tree-like figure, showing the course of evolution of the 
group, and based upon anatomical and enbryological observations. 
The following are the chief results which are discussed : — - 
The Proto-Tunicata were derived from the Proto-Chordata by 
degeneration and modification, and they are represented at the 
present time by the Appendiculariidae. 
The Proto-Thaliacea and the Proto-Ascidiacea diverged in two 
different directions from the Proto-Tunicata, close to the ancestral 
Appendiculariidae. The Doliolidae and the Salpidae form two diver- 
gent lines from the Proto-Thaliacea. Anchinia is an offshoot from 
the ancestral Doliolidae. 
The Proto-Ascidiacea gave up their free-swimming pelagic mode 
of life and became fixed. This ancestral process is repeated at the 
present day by the free-swimming larva of the fixed Simple and 
Compound Ascidians. The Proto-Ascidiacea are probably most 
nearly represented at the present day by the genus Clavelina . They 
have given rise, directly or indirectly, to the various groups of 
Simple and Compound Ascidians. 
Two chief divergent lines arose from the ancestral Clavelinidae — 
one leading to the more typical Compound Ascidians, and the other 
to the Ascidiidse and other Simple Ascidians. The first of these 
ancestral lines gave rise to Diazona and the Distomidse, and later 
on to the primitive Didemnidae. The Polyclinidae form a side 
branch from the base of the primitive Distomidae. One important 
new family, the Coelocormidae (formed for the reception of Ccelo- 
cormus huxleyi , obtained off the east coast of South America, from 
a depth of 600 fathoms, during the “ Challenger ” Expedition), 
was derived from the primitive Didemnidae, and in its turn gave rise 
to the Pyrosomidae, thus connecting the aberrant and highly 
modified Pyrosoma with the Distomidse, the most typical Com- 
