11 
THE VOYAGE OF H.M.S. CHALLENGER. 
does to the Geodiidse. Subsequent examination has convinced me, however, that the 
analogy here suggested is misleading, and that the Tethyidse are in all probability 
Monaxonid sponges. As this conclusion was not reached till my description of the 
family was completed, an account of it is given in an Appendix to this Eeport. 
The Tetractinellid sponges of the Challenger collection are in an excellent state of 
preservation, all but some ten or twelve being preserved in strong alcohol ; so that I 
have been enabled to make a thorough investigation of the minute as well as the coarse 
anatomy of almost every species. This has been a work involving some labour : several 
thousands of thin slices have been cut, and hundreds of other preparations made 
according to methods which will be found described in the chapter on Technique. 
As no complete system of the Tetractinellida has yet been published, I gladly availed 
myself of Mr. Murray’s kind permission to enlarge the ^cope of this Report by including 
an account of all other species of Tetractinellida known to me, besides those contained in 
the Challenger collection. These additional species are treated separately in appendixes 
to each family. 
The number of species and varieties of Tetractinellida obtained by the Challenger is 
87, of which 73 are new to science; they are arranged in 38 genera, of which 18 are 
new; of additional species described in this Report there are 221, and of additional 
genera 45, of which 15 are new. 
The total number, therefore, of described species of Tetractinellida, inclusive of the 
doubtful family Epipolasidse, is 294, and of accepted genera 81. 
My best thanks are due and heartily tendered to those distinguished zoologists who 
have helped to render a system of the Tetractinellida possible by furnishing me with the 
requisite material. To Professor Agassiz I am especially indebted since he sent me across 
the Atlantic the whole, or nearly the whole, of the “ Hassler ” collection of Lithistids, 
including many unique specimens, the originals of 0. Schmidt’s descriptions, and no less 
to Professor von Graff, who, with a generosity which I can only refer to as lavish, 
furnished me with an almost complete series of examples from 0. Schmidt’s types of 
Adriatic sponges. I am also deeply indebted to Professor Perrier of Paris and Dr. Ernest 
Ziegler of Strasburg for many examples of other sponges described by 0. Schmidt, and 
to Professor Stewart who gave me every assistance in the examination of specimens 
described by Bowerbank and now preserved in the Royal College of Surgeons. Especial 
thanks are due to Mr. S. 0. Ridley, who has constantly helped me to specimens, and 
who placed at my disposal for examination all the specimens in the fine collection of 
Tetractinellid sponges preserved in the British Museum, where are to be found most of 
Bowerbank’s species, and specimens of many of Carter’s and 0. Schmidt’s, together with 
a host of miscellaneous examples, all well arranged and readily accessible, — ^^thanks to 
Mr. Ridley’s labours in this department. To my friend and colleague Professor E. 
Perceval Wright, who presented me with parts of several important type specimens. 
