xlv SCIENCE PROGRESS. 



Although the scientific papers of this author have long been known to 

 the specialist and advanced student, till now Prof. Haswell has been 

 comparatively unknown to the elementary student in this country. 



When we look at the latest editions of our scientific text-books we 

 see all of them steadily increasing in size ; this must be inevitably the 

 case with all branches of science that are actively growing. Comforting 

 as these signs of activity may be to the advanced student, the beginner is 

 likely to be terrified when he sees the number of pages which he has to 

 master even to make himself familiar with the rudiments of a science. 

 The present work, we are afraid, will not reassure him in this respect, 

 for it consists of no less than 1400 pages, and yet, as the authors state, 

 is strictly adapted to the needs of a beginner. One must, however, 

 remember that the 1200 illustrations considerably reduce the bulk of the 

 text and renders the same clear and easy of comprehension. Still we 

 cannot help thinking with regret that the large size of this work, and 

 consequent large price, will keep it out of the hands of many of our ele- 

 mentary students who stand in great need of a good text-book of zoology. 



For a text-book of zoology our authors pursue a novel course and 

 one that will undoubtedly commend itself to the beginner with no 

 previous knowledge of the subject. An example of each important 

 class is carefully considered in detail before proceeding to formulate the 

 distinctive characters of the group, then follows the classification and a 

 consideration of the chief variations in structure and development met 

 with in the class, and, finally, a paragraph dealing with the inter- 

 relations of the different orders, this being in all cases terminated with 

 our old and much-abused friend the phylogenetic tree. Many will no 

 doubt object to these " diagrams illustrating the mutual relationships of 

 the class," but, after all, they are almost necessary for the beginner and 

 serve a useful purpose if the latter will only study the conclusions upon 

 which they are based, and remember that they are only attempts to 

 interpret the known facts of morphology, embryology and palaeontology. 



For the benefit of the beginner the subject is introduced by a 

 chapter on structure and physiology, and here we must put forward a 

 strong protest against the unfair treatment which the spermatozoon 

 meets with, thus we find it stated that the Metazoa originate from a 

 single cell, the ovum, thus ignoring the cell-value of the spermatozoon 

 and regarding the latter merely as the impulse to development. Surely 

 sufficient is now known of the development of the two sexual cells to 

 prove that the ovum and spermatozoon are morphological equivalents 

 and that the ovum, save in the still little-understood parthenogenesis, 

 can no more give rise to an embryo by itself than can the spermatozoon. 

 The equal value of these two elements might be demonstrated even to 

 the elementary student if the last two divisions of the sperm-cell had 

 been given, in addition to the maturation of the ovum, which, taken 

 alone, is almost inexplicable to the beginner. In this same chapter we 

 find Fol's " Quadrille of the Centrosomes " cropping up again, notwith- 

 standing the fact that Boveri and others have long shown that theory 

 to be erroneous. We sincerely hope this will be removed from the next 

 edition and a less prominent role assigned to the centrosome, which is 



