October 29, 1886.] 



8CIEJN'CE. 



399 



These cortical eentres are not the places where 

 the crude sensations are received, but the places 

 where they are elaborated, interpreted, and associ- 

 ated with other impressions. They are percep- 

 tive centres. 



The work of Luciani and Seppilli is an onward 

 step in this difficult subject, and can be recom- 

 mended as the best book to use for those who have 

 only time for one book. WhUe it leaves many 

 problems unsolved, it gives hopes of a solution, 

 and leaves the conviction that we are on the path 

 towards a scientific and rational conception of the 

 functions of the highest product of evolution, — 

 the human cortex. Joseph Jastrow. 



THE SEPARATE SYSTEM OF SEWERAGE. 

 The respective merits of the separate and the 

 combined systems of sewerage are still topics of 

 animated discussion among sanitary engineers. 

 Experts are not at one upon the question whether 

 there should be one set of sewers through which 

 should be removed the discharges from human 

 beings and the water which in the form of rain 

 falls upon the surface of the ground, or whether 

 two separate and distinct sets should be construct- 

 ed, each of which should be restricted to the 

 removal of one of these varieties of waste ma- 

 terial. The writers of this little book of 183 

 pages are advocates of the separate system, and 

 believe that its moderate cost makes it possible to 

 carry out a system of sewerage in many cases 

 where the expense of the combined system would 

 make the construction impossible. Most of the 

 literature upon this subject is. to be found in 

 pamphlets, and papers presented to scientific so- 

 cieties, which are not available for general refer- 

 ence ; and the authors have endeavored to supply 

 a deficiency which their own experience has 

 shown to exist by preparing the work now before 

 us. Their aim has been to explain what the 

 separate system is, what it is designed to do, and 

 to give practical directions for designing and con- 

 structing sewers in accordance with that system. 

 They recognize the fact that no single design is 

 applicable to every case, but that each town will 

 present some features peculiar to itself, and that 

 the general plan must be modified to suit the 

 conditions of each case. The dangers connected 

 with, and indeed inseparable from, the old-style 

 yard vaults and cesspools, in which filth accumu- 

 lates oftentimes for years, are graphically por- 

 trayed ; and the ordinary methods by which wells 

 and streams become polluted are plainly and con- 

 cisely explained. These are made a text for a 



The separate system of sewerage : its theory and con- 

 struction. By Cady Staley and George S. Pierson. New 

 York, Van Nostrand, 1886. 



homily upon the need of sewerage in aU densely 

 populated neighborhoods. The evils of the com- 

 bined and the advantages of the separate system 

 are contrasted ; and the authors then pass on to 

 the consideration of the designing of plans for 

 the construction of a sewerage system, commen- 

 cing with the preliminary survey, and carrying 

 them up to the condition of completion, with the 

 house-connections made, and the sewage on its 

 way to the sea or other point of discharge. The 

 volume is, considering its small size, a very com- 

 prehensive one, and will undoubtedly be of oreat 

 service to those engaged in practical work of this 

 kind. 



CHALLENGER REPORTS. 



This bulky volume contains the second report 

 of Professor Herdman on the Tunicata. compris- 

 ing four hundred and thirty-two pages and fifty 

 plates, and Theel's second part of the report on 

 the Holothurioidea, with two hundred and ninety 

 pages and sixteen plates. The high standard of 

 mechanical execution which has characterized 

 previous volumes is fully maintained in both text 

 and plates. 



Professor Herdman's first report treated of the 

 simple ascidians. The present one is devoted to 

 the compound fonns ; and a final part, to discuss 

 the pelagic groups, will probably appear next 

 year. It was at first supposed that the forms re- 

 maining after the simple ascidians had been de- 

 scribed could be disposed of with comparative 

 brevity ; but the compound ascidians proved, on 

 careful examination, to be a much larger and 

 more varied group than had been anticipated. 

 On account of the difficulty in finding good 

 diagnostic characters, and of the similarity which 

 different species sometimes show in their external 

 appearance, it has been necessary to submit near- 

 ly all the species in the collection to a detailed 

 histological examination, and portions of most of 

 them have had to be sectionized — a slow and la- 

 borious proceeding — before the relations of their 

 different parts could be satisfactorily determined. 

 Then, in the case of a few species, some interest- 

 ing peculiarities in regard to reproduction by 

 gemmation required a careful and lengthened ex- 

 amination, on account of the important bearing 

 of these features upon the mode of formation of 

 the colony. 



The collection of compound ascidians represents 

 one hundred and two species and varieties, ar- 

 ranged in twenty-five genera. Eighty-eight of 

 the species and ten of the genera are here de- 



Report of the scientific results of the voyage of the ■ 

 Challenger during 1873-76. Vol. xiv. : Zoology. London, 

 Government, 1886. f°. 



