i8 95 . SOME NEW BOOKS. 423 



free mode of life. Other classes relinquished it at an earlier period 

 in their history, and of these the Hoiothurians, says Dr. Lang, were 

 the first to become free. They remained attached, however, long 

 enough for five food-grooves with their rows of tentacles to be 

 developed. But as the various classes became free, and took in food 

 directly by the mouth, these food-grooves gave up their original 

 function, and they with their underlying nerves became transformed 

 into the subepithelial radial nerves with their epineural canals. I 

 myself suggested, in 1889, that while radiate symmetry was, in 

 the case of Echinoderma, due to fixation, the special case of pen- 

 tamerous symmetry was induced by its mechanical superiority to 

 the tetramerous or hexamerous type, and that pentamerism in 

 Hoiothurians might be due to the fact that they were descended from 

 ancestors in which the typical skeleton was better developed (Quart. 

 Jouvn. Geol. Soc. xlv., p. 166). It is interesting to find that Dr. Lang 

 is brought by his views to a similar suggestion. Or is he adopting 

 mine ? We cannot tell. 



It is, however, impossible to agree with Dr. Lang that the 

 ancestor (Stammform) of the Crinoids had a determined composition 

 of the dorsal cup, viz., five infrabasals, five basals, five radials, and 

 the anals. Either there were two ancestral types, one with infra- 

 basals, the other without ; or the dicyclic type was derived from the 

 monocyclic by a modification of the cup-plates. In either case, 

 the anals were a secondary development. 



From such an attached " Crinoid-phantom," as the Sarasins 

 would call it, Dr. Lang derives the Echinoids, Ophiurids, and 

 Asteroids. His belief that the Echinoids are descended from 

 attached ancestral forms with arms is due to the fact that the gonads 

 have become influenced by the pentamerism, and must, therefore, 

 have originated as fertile outgrowths of the axial organ contained in 

 arms. The Ophiurids branched off later still, and the Asteroids 

 were last of all to adopt a free life, an idea confirmed by the tem- 

 porary fixation of the larva still seen in their ontogeny. 



These ingenious views present many difficulties, to some of which 

 allusion has been made ; but they are distinctly stimulating and 

 worthy of careful study in the original. Fortunately, a translation of 

 this book, by Mr. and Mrs. H. M. Bernard, is being published by 

 Messrs. Macmillan, so that English students will soon have an 

 opportunity of carefully considering Dr. Lang's ideas. Despite the 

 slips to which I have thought it right to call attention, the book is a 

 wonderful compendium of our knowledge of the Echinoderma, 

 clearly written and beautifully illustrated. It concludes with a short 

 but adequate account of the Enteropneusta, the larval forms of which 

 have been shown by recent research to indicate some- remote con- 

 nection with the ancestral Echinoderm stem. F. A. Bather. 



Three Books on Botany. 



Lehrbuch der Botanik fur Hochschulen. Von Dr. Eduard Strasburger, Dr. 



Fritz Noll, Dr. Heinrich Schenck, Dr. A. F. W. Schimper. Gr. 8vo. Pp. vi., 



558, with 577 illustrations. Jena : Gustav Fischer, 1894. Price 7 marks. 

 A Student's Text-book of Botany. By Sydney H. Vines, M.A., D.Sc, F.R.S. 



8vo. Pp. xvi., 821, with 483 illustrations. London : Swan, Sonnenschein & Co., 



1895. Price 15s. 

 A Hand-book of Systematic Botany. By Dr. E. Warming, with a revision of the 



Fungi, by Dr. E. Knoblauch. Translated and edited by M. C. Potter, M.A., 



F.L.S. 8vo. Pp. xii., 620. London: Swan, Sonnenschein & Co., 1895. 



Price 15s. 



