i8 9 6. SOME NEW BOOKS. 345 



numerous notes by the original authors as well as by the two 

 competent translators. For the present volume, which deals with 

 Porifera, Cnidaria, Ctenophora, Platyhelminthes, Orthonectidae and 

 Dicyemidae, Nemertini, Nemathelminthes, Acanthocephali, Rotatoria, 

 Annelida, Sipunculidae, Chaetognatha, Enteropneusta, and Echino- 

 derma, 130 additional papers have been consulted. While there are 

 no additions to the literature of Ctenophora, there are no less than 

 thirty to that of Echinoderma, and this without reckoning the 

 numerous papers on experimental embryology, most of which have 

 dealt with the echinoderm ovum. No papers after 1894 are included, 

 so that the latest important works by Bury and MacBride are not 

 discussed. With regard to the general questions of the homologies 

 and relations of the classes of Echinoderma, the authors hold views 

 with which we agree in the main. For instance, " Even the 

 conception of the homology of the plates founded by Loven and 

 championed by Carpenter, especially those which in the different 

 groups of Echinoderms lie about the apical pole, is not to be con- 

 sidered as assured." They reject Semon's ancestral Pentactaa, 

 thinking it " more justifiable to search for the ancestral forms of the 

 Echinodermata among the existing material which is offered to us by 

 palaeontology." The search will, we fear, take a long time. It is recog- 

 nised that the origin of the radial structure must have been due to 

 fixation, hence the common ancestor is sought among stalked forms ; 

 this is not absolutely necessary, for the evolution of a true stalk was a 

 slow process, and mere fixation would probably have effected all that the 

 theory requires. The Cystidea are no doubt the most ancestral of the 

 known classes, for we agree with the authors in regarding the Holo- 

 thurioidea as degenerate in some respects ; but there have yet been 

 found no certain transitions between the Cystidea and the other classes, 

 except perhaps some of the Crinoidea. As to the internal structure of 

 the primitive Cystid — that elongate sac, devoid of radial symmetry, 

 with irregular plates developing in its integument, and attached by 

 what was the pre-oral lobe of its young — we know nothing. Here 

 embryology should shed its light, but affords the merest glimmer. 

 The forms of the larvae have been to a large extent secondarily 

 acquired, and the very one that should be of most help is the most 

 modified, namely, the crinoid larva, that is to say in Antedon, where 

 alone we know it. It seems probable that the ancestor was 

 bilaterally symmetrical, and to some extent segmented. The 

 affinities with the Tomavia of Balanoglossus will doubtless serve as 

 our best clue. 



We cannot leave this subject without observing that an account 

 of the development of Antedon that takes no note of the anal plate, in 

 either text or figures, is singularly deficient. There is also an 

 inadequacy in the account of the infrabasalia, which do not always 

 have the same arrangement, so that the comparison with the 

 Ichthyocrinoidea falls to the ground. It might have been added that 

 the homology of the first formed stone-canal and water-pore with the 

 stone-canal and madreporite of other echinoderms is confirmed by 

 palaeontological evidence, in so far as a similar madreporite is some- 

 times developed in connection with it. In a future edition the slip at 

 the bottom of p. 453, by which Rhizocvinus is printed instead of 

 Antedon, should be corrected, as it alters the meaning of half the page. 



The remainder of this work is to be translated by Dr. 

 H. J. Campbell, of Guy's Hospital Medical School, who will doubt- 

 less be as successful as Drs. Mark and Woodworth, and who will, let 

 us hope, steer clear of their " fundamental " error. F. A. B. 



