EEPOET ON THE TUNICATA. 
the elucidation of the same process in other Compound Ascidians, and an important 
memoir in Eussian on their embryology by Ganin, appeared about the same time. 
Giard’s large work on the Ascidige Composite, published in 1872 , added greatly to 
the knowledge of the group. It contained careful descriptions of a number of new 
forms, and the definitions and arrangements of the families and genera, many of which 
were new*, formed welcome and much needed aids to classification. 
Since that date most of the works upon the Tunicata have dealt either with 
the Simple Ascidians or with the Thaliacea, but Della Valle in Italy, and von Drasche 
in Austria, have done good service in describing new forms amongst the Compound 
Ascidians, and the last named author has published in his Synascidise of the Gulf 
of Eovigno, a series of probably the most beautiful and life-like plates of Compound 
Ascidians which have yet appeared. Della Valle has also contributed considerably to 
our knowdedge of the processes of gemmation in the various groups of the Ascidise 
Compositse, but this question will have to be gone into more in detail further on in the 
present work. 
Lastly, the Challenger Expedition has added a large number of new forms to 
the list of Compound Ascidians previously known, and some of these, besides the 
interest attaching to them on account of the localities or the great depths at which 
they were collected, have remarkable anatomical peculiarities, which render their 
discovery of some importance in the history of the group. 
