52 



NA TURE 



{Nov. 18, 1880 



Mr. Norman, Mr. Peach, Dr. Mcintosh, Prof. Ray 

 Lankester, and others who have given him valuable aid 

 in his work, gives an account of the structure of the 

 Polyzoa generally, with some details concerning their 

 development, life-history, and distribution. Several pages 

 are devoted to the question of the name of the class 

 concerning which it seems almost hopeless that any 

 unanimity amongst naturalists will be attained. The 

 author adopts J. V. Thompson's term Polyzoa on the 

 ground of priority, and we hope it may prevail in this 

 country, although it is scarcely probable that Continental 

 zoologists will, as the author trusts, "reconsider the 

 grounds on which they have hitherto given their adhesion 

 to Ehrenberg," and give up the term Bryozoa (^Moos- 

 ihie7-cJien'). 



Several pages are devoted to the question of the nature 

 of the "brown bodies," which the author, following Prof. 

 F. A. Smith and from his own extended observations, 

 formerly considered to be essentially concerned in the 

 production of new polypides by germination. He now 

 admits that the evidence at present tallies better with the 

 residuary theory of Nitsche and Joliet, who, as is well 

 known, regard the bodies as merely remains of decayed 

 jjolypides, but thinks that further investigation on the 

 '.natter is yet required. An interesting series of wood- 

 cuts are given illustrating, as shown in a series of dif- 

 ferent species, the development of the avicularium 

 from the first rudimentary stages, hardly distinguishable 

 from the ordinary zooecium, up to its most highly 

 specialised bird's head-like form. Most readers are 

 familiar with Mr. Darwin's account of his experiments on 

 the avicularia of Polyozoa made during the voyage of the 

 Beagle and published in his Journal. The author after 

 citing these, and those of Mr. Busk and others, expresses 

 himself as inclined to regard the avicularia as " charged 

 with an offensive rather than alimentary function," 

 believing that their vigorous movements and the snapping 

 of their formidable jaws may drive away loafing annelids 

 and other enemies. 



Some short account of the embryonic development of 

 the Polyozoa is given, and is illustrated by a coloured plate 

 of larvae taken from the splendid monograph on the 

 subject by Dr. J. Barrois of Lille. In the matter of 

 classification the author follows Ray Lankester as far as 

 the main sub-classes are concerned, dividing the class 

 according to the characters of the lophophore into the 

 Holobranchiata, or those which have the tentacles in a 

 continuous series, and the Pterobranchiata, in which the 

 lophopore is broken into two distinct arms like those of 

 Brachiopods. The Pterobranchiata include only a single 

 genus, the remarkable Rhabdopleura of Allman. The 

 Holobranchiata are divided, after Nitsche, into the Ecto- 

 procta, in which the anal orifice lies without the lopho- 

 phore, and the Entoprocta, in which the orifice lies 

 within it. The latter group includes the genera Pedicel- 

 lina and Loxosoma only, whilst the main mass of the 

 existing Polyzoa come under the Ectoprocta, the marine 

 forms of which form a single order, GymnolKmata of 

 jMlman, which order is divided by the author accord- 

 ing to Mr. Busk's well-known system into the sub-orders 

 Cheilostomata, Cyclostomata, and Ctenostomata. The 

 generic terms adopted in the work are however in many 

 instances different from those employed by Mr. Busk and 



other former authors, and many familiar species have 

 changed their names, so that the student is somewhat con- 

 fused. Thus the species hitherto ranged under the genus 

 Leptalia are separated into sections and- placed under 

 the author's three genera, Mastigophora, Schizoporella, 

 Schizotheca, and other genera. 



As before stated, the number of British species of 

 marine Polyzoa described in the work is 235. Of these 

 69 have as yet not been found elsewhere, but as the 

 author adds, no inference as to their range can be drawn 

 from this negative fact. For 28 species Shetland is the 

 only British locality, 8 of these not being found elsewhere, 

 whilst the remainder are Arctic forms, with the exception 

 of two, one of which, CeUaria johnsoiii, ranges as far 

 south as Madeira, and is 'abundant in the Mediter- 

 ranean. Some of the British species have an extraordi- 

 narily wide range. Thus CeUaria fistulosa occurs in the 

 Mediterranean at Madeira, in South Africa, in Scandi- 

 navia and North America, in the Indian Ocean, and in 

 Australia and New Zealand. And there are several similar 

 instances of almost world-wide distribution, the species 

 not being deep-sea forms, but such as flourish between 

 tide-marks and in shallow water, though also found at 

 greater depths. The author suggests as a possible explana- 

 tion of the wideness of range of such species, in addition 

 to migration along coast lines and in profound depths, 

 the agency of currents, floating timber, and ships. There 

 is a very close resemblance between the Polyzoan fauna of 

 the south-west coasts of France and our own, whilst a small 

 group of Polyzoa is common to our shores and those of 

 South Africa ; but these are also Mediterranean. The 

 author expects that a flood of light will be thrown on the 

 subject of the distribution of the Polyzoa by the results of 

 the Challenger Expedition, when published. It is obvious 

 that in treating of any branch of the marine fauna of a 

 restricted area, such as the British Isles, it will be neces- 

 sary to make some restriction as to depth in considering 

 questions of distribution. Once the abyssal fauna is 

 reached by the dredge the animals obtained have no 

 longer any special connection with the shores off which 

 they are obtained, but belong to the ocean bottom and 

 are mostly cosmopolitan, or rather Oceanopolitan. 



The cordial thanks of zoologists are certainly due to 

 Mr. Hincks for having produced this most useful work. 

 It will be valuable not only to the professed naturalist, 

 but also an entertaining addition to the sea-side libraries 

 of those who work occasionally with the microscope for 

 recreation. 



OUR BOOK SHELF 



A Popular History of Science. By Rob. Routledge, B.Sc. 

 (London ; George Routledge and Sons, 18S1.) 



I^f looking through many of the works on popular science 

 one is inclined to exclaim, " Oh, monstrous ! but one half- 

 pennyworth of bread to this intolerable deal of sack." 

 Mr. Routledge's recent volume is fortunately an exception 

 to this rule, for in it we find a clear and concise statement 

 of the development of the main branches of physical 

 science given in a readable form with such an amount 

 of biographical notices as to impart a human interest to 

 the tale. Extracts, too, from the writings of the great 

 workers in science have been judiciously interspersed 

 throughout the text, thus bringing the student into direct 

 communication with the master mind. Numerous illus- 



