126 



NA TURE 



[December 3, 1908 



with disease of the nervous and circulatory systems, 

 the internal organs, &c. 



Its concluding chapter is on heredity in diseases 

 of the eye. As an introduction to this subject, the 

 author has included a brief exposition of the Men- 

 delian theory of inheritance, taken from a paper by 

 Mr. R. C. Punnett, in the Proceedings of the Royal 

 Society of Medicine. 



This treatise, as we have already said, is the most 

 complete work of its kind hitherto published. In our 

 opinion it is an extremely valuable addition to 

 ophthalmolog-ical literature, and one which is indis- 

 pensable to all those engaged in the study of ocular 

 pathology. 



There are two special features of Dr. Parsons's book 

 to which attention may be directed. One is the ad- 

 mirable way in which the author brings together and 

 discusses the various theories which at different times 

 have been brought forward in explanation of the 

 pathology or pathogenesis of ocular disease. A good 

 example of this is to be found in the chapter on 

 sympathetic ophthalmitis. 



The author's decisions appear to be strictlv judicial, 

 but he is perhaps rather lenient in reference to theories 

 or statements which have been shown to be hardly 

 worthy of support. 



The other feature is the very full and most valuable 

 list of references to literature provided throughout the 

 book. Following the method of a well-known writer 

 of travellers' guides. Dr. Parsons affixes an asterisk to 

 the works which he believes to be most important, 

 but, like the hotels in the guide, there is sometimes 

 room for difference of opinion as to the merits of the 

 " starred " articles. 



In its general attributes. Dr. Parsons's work de- 

 serves commendation, and very little adverse criticism 

 is called for. The author's literary style is usually 

 clear and decisive, though it often lacks smoothness 

 and elegance. It is no discredit to him that in the 

 course of so extensive a work some pages should 

 contain a few crude or cryptic sentences. There are 

 but few printer's errors, but some of them ought 

 not to have escaped notice, e.g. the printing of the 

 word " sarcoma " for " glaucoma " in vol. iii., p. 1072. 



The illustrations, which are very numerous, are, 

 with few exceptions (e.^. several in the chapter on 

 the retina), very satisfactory. The large majority are 

 from photographs, and have, therefore, the merit of 

 unquestioned fidelity, even if they are less explicit 

 (especially in high-power reproductions) than draw- 

 ings. 



.A. careful index of illustrations and of subjects is 

 given in vols, i., ii., and iii. Vol. iv. has an index of 

 the subjects contained therein, but lacks an index of 

 illustrations. In this volume there is also a general' 

 index of subjects in all four volumes, but, unfortun- 

 ately, it is of little use. The value of a general index 

 in a work of more than one volume is to enable the 

 reader to ascertain quickly in which volume he will 

 find the subject under discussion. It is no assist-- 

 ance to him to learn that it is on p. 1339, unless he 

 is informed in which volume this page is to be found. 

 NO. 2040, VOL. 70] 



.4 STUDY IN SEAWEEDS. 

 Die .Algeiiflora der Daiiziger Bucht, ciii Bcitrag zur 

 Kcnntnis der Ostseeflora. By Prof. Lakowitz. 

 Pp. vii + 141;' I Vegetationskarte, 5 double 

 plates of photographic illustrations of the plants, 

 and 70 text-illustrations of structure. (Danzig, 1907, 

 Kommissions verlag von W. Engelmann, Leipzig.) 



THIS monograph is devoted to a most careful 

 study of the marine flora (excluding diatoms) 

 of a region which, though poor in species, affords 

 problems of great scientific interest, more especially 

 with respect to the origin of the flora and its com- 

 parison with those of other seas. The whole number 

 of species determined with certainty amounted to 

 onlv seventy-four, including four Characeae, but to 

 these must be added a few others met with only in 

 too imperfect a state to allow of determination. 



Only one species, belonging to the genus Gonio- 

 trichum, is regarded as new to science, but six 

 varieties receive mention as previously unrecorded. 

 The species and varieties are described as they exist 

 in the Gulf of Danzig; their environment is noted, 

 and their distribution within and beyond the Baltic 

 Sea is quoted from the best works. While the de- 

 .scriptions, analytical keys, and figures make the first 

 part of the monograph a valuable contribution to 

 systematic botany, a more general interest attaches 

 to the second part, in which are treated the relations 

 of the flora to the environment within the bay, and 

 to the floras of other regions. The physical con- 

 figuration of the region is discussed, as well as the 

 geological structure, and the elevations and depres- 

 sions which can be traced as having occurred in 

 the past. 



There is evidence that the district lay under the 

 Scandinavian ice-sheet for a time, and that, as the 

 ice retreated northwards, the connection of this sea 

 was with the cold northern seas, over sunk portions 

 of what is now Sweden, Arctic Mollusca (Yoldia 

 arctica, Aslarte borealis, &c.) being characteristic of 

 its fauna. The melting of the ice led to the forma- 

 tion of a sea with very cold water, poor in the usual 

 marine salts. It appears to have been shut off from 

 the present west part of the Baltic by a ridge passing 

 through Bornholm. During this period probably the 

 bulk of its fauna and flora arrived, about one-half 

 of the Algae showing an Arctic character. Subse- 

 quently, for a time, the eastern Baltic became a 

 lake, to be afterwards again connected with the 

 North Sea, but by a more southern outlet. The 

 degree of salinity varied much in consequence of 

 geological changes, which must have greatly affected 

 the flora. Its poverty in species is very marked when 

 compared with the 255 species recorded from the 

 western Baltic, which has long been united w-ith the 

 North Sea, as at present. The less salinity has pre- 

 vented the immigration of some species ; and is prob- 

 ably the cause of physical peculiarities in others, such 

 as the slender forms and smaller size. The Danzig 

 algal flora tends to be characteristic of brackish water 

 rather than of the sea. Several species are of 



