440 THE ZOOLOGIST. 



branch and the sponge or seaweed) have been associated and exposed 

 to the same influences for unnumbered ages. Thus, whatever may 

 be the causes which tend to give a sponge a certain appearance, they 

 must also affect the Dorid which lives on the sponge, at least so far 

 as they are external and concerned with water, temperature, and 

 general surroundings." 



In a footnote it also stated — 



"that not only do Dorids resemble sponges (where the resemblance 

 is advantageous to the Dorids), but also sponges resemble Dorids 

 (where no such advantage to the sponge is clear)." 



We are still in the wood of speculation ! 



There is as an appendix a useful bibliography of books and 

 papers dealing with the Nudibranchiata of the Atlantic (including 

 the Mediterranean and Caribbean Seas), which have been pub- 

 lished since the completion of Alder and Hancock's Monograph 

 in 1855, and there are eight beautifully coloured plates. 



A History of British Mammals. By Gerald E. H. Barrett- 

 Hamilton, B.A., F.Z.S., &c. Gurney & Jackson. 



The first part of Barrett-Hamilton's British Mammals has 

 now appeared ; it has been much anticipated, and, we are told, 

 " its author has had its production before him for over twenty 

 years." It is announced that the work will consist of three 

 sections, dealing respectively with the Bats, the Land Mammals, 

 and the Marine Mammals. 



It is impossible to give from this part alone any adequate notice 

 of the publication, as even the General Introduction to Bats is 

 unfinished, and announced to be completed in parts ii. to vi. 

 No one, however, can miss the recognition of its thoroughness 

 in treatment and its wealth in reference. We must await the 

 completion of a section before attempting to more fully review it. 



