Bibliographical Notices. 227 tke contractile vesicle. If effective informing^ it could not bj anj stretch of the imagination be truly regarded as the efficient cause in the almost instantaneous reflux into the mass of the bodj-substance of the ectosarc constituting the contractile vesicle. Besides, according to Dr. Gruber, the pressure he refers to is exercised at the jjosterior aspect of the Amoeba^ and since the contractile vesicle almost always discharges itself in that region, it would be doing so in the teeth of the very force which is, at the very same time, exerting itself in projecting pseudopodia in the opposite direction to the con-tractile vesicle. Having for the present brought these observations to a close, it only remains for me to assure Dr. Gruber that I am extremely glad to find that so able a writer and thinker has been led, although by a different route, to conclusions concern-ing the relations between endosarc and ectosarc, and the pheno-menon of pseudocyclosis, similar to those arrived at by me so many years previously. BIBLIOGRAPHICAL NOTICES. Australian Museum. Catalogue of the Australian Hydroid Zooiohytes. By W. M. Bale. Sydney : 1884r. The publication of the ' Catalogue of the Australian Hydroid Zoophytes,' printed by order of the Trustees of the Australian Museum, has supplied a want which has long been felt of a detailed and critical account of the various species of Hydroids which have been described from the Australian seas. Many of the older species are known only by very brief descriptions, which, however admirable at the time at which they were framed, have been rendered, more especially in the absence of illustrative figures, altogether indefinite, owing to the numerous allied forms which have since come to light. The present Catalogue contains, besides the description of a large mimber of new or lately known forms, redescriptions or amended descriptions of many of these older species in those eases where their identification has been possible, while supplementary characters and original remarks, often with considerable detail, on many of the genera and species which are described give additional value to the. work. A special feature of the Catalogue is the large number of figures which are given, and which, with but few exceptions, are from original drawings. It will thus be seen that the work is a valuable contribution to the literature on zoophytology, and will form an important landmark in the history of the Australian zoophytes.