Amphioxus and the Ancestry of the Vertebrates. By Arthur Willey.
With a Preface by H. F. Osborn. (Macmillan and Co.)—This work, issued as No. II. of the "Columbia University Biological Series," forms another of the valuable contributions to science which we have lately received from America. The Amphioxus, or Lancelet, though a small, insignificant-looking creature, found burrowing in sandy coasts, is yet one of the most interesting animals in the world, from a biological point of view, for it is regarded as a surviving form lying in the direct course of transi- tion from the Invertebrates to the Vertebrates. This is shown in Dr. Willey's grouping of the lower Vertebrates, or Protochordata, which he discusses in this volume :—Division 1, Hemichorda (Balanoglossus, Cephalodiscus, and Rhabdopleura); Division 2, Urochorda (Ascidians) ; Division 3, Cephalochorda (Amphioxus). The Amphioxus is said to have been "one of the few animals not known to Aristotle ;" a somewhat odd expression, considering how very small a proportion of the animals now known to us were known to Aristotle at all. It appears to have been first described by Pallas in 1778, who received a specimen from Cornwall in spirit, and he regarded it as a slug; but in 1834, Costa, who had found it on the shores of the Gulf of Naples, recognised that it was a fish. Since that time many authors have written on the Amphioxus and its remarkable affinities ; but their observations are widely scattered through numerous publications in various languages, and it is a real boon to the zoological student to have the substance of what is known at present on this interesting subject compressed into the limits of a handy volume. The book is divided into three sections ; the first dealing with Amphiorus, its form, anatomy, development, larval forms, &c. ; the second with the Ascidians, and the third with the Protochordata in relation to the problem of vertebrate descent. The frontispiece represents the Amphioxus in various positions, both swimming in the water and burrowing in the sand, and there are one hundred and thirty-five excellent woodcuts scattered through the book. There is a good classified bibliography of one hundred and thirty- three items, and the volume closes with an alphabetical index. Much of the book is purely descriptive and technical ; but we may conclude our present notice by stating the author's opinion that "one of the chief factors in the evolution of the Vertebrates has been the concentration of the central nervous system along the dorsal side of the body (in contrast to the position of the longitudinal nerve-core of Annelida, &c., along the ventral or locomotor surface), and its conversion into a hollow tube."
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