2 
THE VOYAGE OF H.M.S. CHALLENGER. 
reasons the present part of the Report, though including only the Compound Ascidians, 
has taken longer to prepare and has reached a larger size than was expected. A 
description of the pelagic forms (the Pyrosomidse, the Appendiculariidse, and the 
Thaliacea), forming the third and concluding part of the Report, will probably appear 
during the next year. 
The large collection of Ascidise Compositse, which was for the most part found to 
be in good condition for histological examination, represents one hundred and two 
species and well-marked varieties, arranged in twenty-five genera. Eighty-eight of the 
species and ten of the genera are new to science. As no preliminary report upon 
the Compound Ascidians was published, these new genera and species are described here 
for the first time. I have found it necessary to form two new families, the Coelocormidse 
and the Polystyelidee. 
The Compound Ascidians collected during the cruises of H.M.SS. “Lightning” and 
“ Porcupine” in the summers of 1868-70 were sent to me by Mr. Murray for examina- 
tion. They have been incorporated in the Challenger collection, and the descriptions of 
them will be found in the Systematic Part of this Report.^ 
Since the publication of the first part of the Report, several specimens of Simple 
Ascidians belonging to the Challenger collection, which had previously been over- 
looked, have been sent to me for examination. I have placed the description of these 
forms as an Appendix at the conclusion of this part of the Report. 
1 The Simple Ascidians of the “Porcupine” and “Lightning” expeditions were described in a paper read in 
January 1884, before the Koyal Society of Edinburgh, and published in its Transactions {Trans. Boy. Soc. Edin., 
vol. xxxii. part ii. p. 219). 
