June i6, 1898] 



NATURE 



149 



It of the region of probabilities, but in spite of the careful 

 •searches made in my laboratory by A. G. Bourne and 

 thers, I have not yet succeeded in so doing. After all, it 

 should be possible, by modern improved methods, to test 

 ■this question of continuity in Hirudo by means of actual 

 injection. There are "other animals," it must be remem- 

 Ijered, in which there is free communication between the 

 ccelom and the vascular system, to wit, the not unim- 

 portant animals known as \'ertebrata. 



In his classification of the MoUusca, Mr. Sedgwick 

 has taken his own line, and refused to follow Pelseneer 

 in the separation of the Chitons from the Gastropoda, 

 though he places Neomenia and Chietoderma in a 

 separate class, the Solenogastres, for very good reasons 

 which he sets forth. 



The creation of a separate phylum for each of the small 

 groups of Sipunculoidea, Priapuloidea, and Phoronidea 

 is perhaps legitimate in the present state of knowledge, 

 though the questions involved are of a very difficult 

 nature, and the facts known insufficient to give one great 

 confidence in any of the proposed classifications affecting 

 those animals. 



Mr. Sedgwick excludes the Platyhelminthes, the 

 Nermertea, the Nemathelminthes, and the Rotifera from 

 the Ccelomata ; but he does not argue at any length the 

 question as to whether there are or are not coelomic 

 rudiments in each of these groups. The pengonadial sacs 

 of Platyhelminthes and Nemertea and their nephridia 

 may be interpreted as modified developments from 

 ccelom, though it would no doubt be difficult to show 

 that they are so. It must, however, be remembered that 

 in such matters the assertion that A is not B is as 

 positive and definite a statement, requiring just as full a 

 proof, as the statement that A is B. 



The chief omission which has to be noted in Mr. 

 Sedgwick's book is that which I have recently pointed 

 out in other works— namely, an insufficient historical 

 account of the discoveries, hypotheses, conceptions and 

 terms (with immediate reference to chapter and verse), 

 the bnnging together and explanation of which is the 

 purpose of the writer's labour. Mr. Sedgwick is not so 

 determined to omit history and the names of contem- 

 porary workers as are some other writers of text-books. 

 He does not make a profession or virtue of this practice, 

 and in many cases gives an immediate reference to a 

 special memoir, or even cites a naturalist's name, after 

 mentioning an important fact or theory. At the same 

 time, he cannot be said to have done what could easily 

 have been done in this respect without materially in- 

 creasing the size of his book. Of course, all such refer- 

 ences and discussions must be in proportion to the size 

 and scope of the text-book in which they should appear, 

 and Mr. Sedgwick not unfrequently does give a historical 

 reference. But why should he not tell us, for instance, 

 who invented the name Protozoa, what he meant by that 

 term, and how it came to have its present limitations 1 

 Why should he not tell us (p. 533) who proposed the 

 separation of Sipunculoidea and Echiuroidea which he 

 adopts ? Why should he not give credit to Dr. Hudson 

 for his most interesting discovery of the six-legged 

 Rotifer Pedalion, instead of printing Hudson's drawing 

 of his discovery with the label "from Perrier after 

 Gosse?" Mr. Sedgwick very properly states in a foot- 

 NO. 1494, VOL. 58] 



note that the classification of the Polychaeta adopted by 

 him is that of Dr. W. B. Benham, to whose work he 

 refers. It would, I think, have helped many of his 

 readers if he had given some account of the source of 

 classification and terms used by him, in all other 

 instances. Putting aside such suggestions for improve- 

 ment, I think we must recognise that Mr. Sedgwick's 

 book is a very good one, ably put together, and likely to 

 be extremely useful ; it is, in fact, not only the last, but 

 the best zoological text-book — so far as the first volume 

 goes — in the language. E. Ray Lankester. 



THE ANALYSIS OF QRES. 

 Methods for the Analysis of Ores, Iron and Steel, in Use 

 at the Laboratories of Iron and Steel Works in the 

 Region about Pittsburg, Pa. Pp. iv -I- 133. (Easton, 

 Pa. : Chemical Publishing Co., 1898.) 



A COLLECTION of the methods in • use in the 

 modern laboratories of steel works must be useful 

 if only for comparison, but the present book cannot take 

 rank with standard works such as those by Blair and 

 Arnold. One notes a sameness in the modes of pro- 

 cedure, varied, however, in some instances by question- 

 able modifications, more especially as regards phosphorus 

 determinations. 



Sufficient attention has not, on the whole, been given 

 to the exact relative proportions of nitric acid, molybdate, 

 &c. Most of the operators are apparently content to 

 assume that it is sufficient to add, in all instances, 

 measured quantities of the reagents required. This is 

 contrary to the writer's experience : each analysis should 

 be conducted in accordance with the conditions observed 

 at the time ; it is not enough to merely add fixed 

 quantities of reagents, but the operator must judge for 

 himself, more especially as regards the use of nitric acid. 

 In practice the best and most accurate results are 

 obtained by the direct weighing of the molybdate 

 precipitate, using the magnesia method only as a check. 

 Volumetric methods are useful where rapid determin- 

 ations are required for check purposes, but are not so 

 trustworthy as the weight method, i.e. when proper 

 precautions are taken and the necessary experience 

 gained. 



Sulphur. — The evolution method cannot be dispensed 

 with in an ordinary steel works, but is only useful for 

 rough determination ; it is little better than a qualitative 

 method, as has been repeatedly demonstrated. 



Apparently we have no better method than with aqua 

 regia and subsequent precipitation with barium chloride. 

 It is well known, however, that discordant results are 

 often obtained. At present a rapid and strictly accurate 

 mode of determining sulphur has yet to be devised ; this 

 for various reasons well-known to analytical chemists. 



As regards the estimation of manganese, nickel, 

 copper, &c., little need be said ; there is not much 

 that is novel in the methods, which are fairly good 

 and are such as are usually practised. The same is 

 applicable to carbon determinations, with the exception 

 of barium hydroxide as an absorbent (A. G. McKenna), 

 which the author recommends ; as also the complete 

 analysis of chrome iron, which appears a mode of 

 procedure sufficiently accurate for all practical purposes. 



