1894. SOME NEW BOOKS. 459 



which the structure of this animal gives rise to are included. Mr. 

 Willey quotes no less than 133 papers which have been consulted by 

 him in the course of preparing the volume now before us, and of these 

 at least 100 may be fairly put down to Amphioxus itself. It is there- 

 fore a saving of much time to the hard-worked zoologist of the present 

 day to have all this in a nut-shell — a cocoa-nut-shell possibly, — but 

 still a work of moderate dimensions. Apart from this merit, the 

 practice of writing a book about a definite animal of interest seems to 

 us to be an excellent plan. It is a pity that not more is done along 

 this line, which was really initiated by Mr, Huxley in his " Crayfish." 

 The anatomy of birds, for example, might be woven into a volume 

 upon such a type as Aptevyx, one upon the Amphibia upon a plain 

 account of the Axolotl, and so forth. 



The present work contains everything that should be known 

 about Amphio.xns, besides a great deal that it is advantageous to know 

 about the Tunicata, Balanoglossus, and some other types which come 

 into structural relations with Amphioxus. Amphioxus was originally 

 put down as a Mollusc, a fate which also overtook another equally 

 remarkable and not less isolated type, Pevipatus ; the Mollusca in the 

 early days of this century and the last days of the seventeenth 

 appear to have been pretty well what the worms are now, a receptacle 

 for anything unclaimed. The Russian naturalist Pallas, the discoverer 

 of the " fish," was responsible for this placing of it; it was not until 

 sixty years had elapsed that Costa redescribed Amphioxus and 

 put it in its proper place, approximately at any rate. Nowadays 

 there are really two parties which surge round Amphioxus; there 

 are those who would look upon it as much degenerate and those who 

 regard its simplicity as a mark of antiquity. There is no doubt much 

 of both in the organisation of the animal. This " exquisite form," as 

 Professor Osborn enthusiastically calls it in the preface which he 

 contributes to Mr. Willey's book, is common in many parts of the 

 world ; it is, indeed, practically world-wide in range, or is represented 

 by a considerable number of species which differ in but slight 

 characters, the number of the myotomes being the chief means by 

 which they are distinguished. Mr. Willey argues from its wide range 

 and the trifling specific differences that the form is extremely ancient. 

 We fully agree with Mr. Willey that the creature is in all probability 

 an extremely archaic form, but his reasoning does not seem to us to 

 prove the fact. In ancient forms it is surely more usual for the 

 differences between species, or genera, as the case may be, to be great 

 rather than small ; intermediate forms have had time to die out, and 

 long isolation has done its work. It is, rather, the newer groups that 

 fade imperceptibly into each other. The very fact that there are so 

 many diverse opinions about the classification of birds is indirect 

 evidence of the comparative newness of the group ; while the 

 strikingly marked lines which divide from each other the several 

 groups of reptiles are confirmatory of their age as shown by the rocks. 

 The number of described species of Amphioxus is eight, but we 

 believe that a ninth species was described at the recent meeting of 

 the British Association at Oxford. 



Amphioxus is, as will be inferred from what we have said concern- 

 ing the bulk of the literatur<5 devoted to it, one of those animals which 

 most naturalists have had dealings with. It is surprising, therefore, to 

 learn how recently the excretory system has been discovered. For a long 

 time the animal was believed to be without any specialised excretory 

 organs of the vertebrate type — a piece of evidence which appeared to 



