144 



NATURE 



[August 4, 19 10 



schizogonv in the intestine of the bug. According to 

 Chagas, the true infective cycle of the parasite in the 

 bug is comprised in four stages : — (i) the encapsuled 

 "zygotes"; (2) the schizogony-forms ; (3) the trypani- 

 form individuals in the body-cavity ; and (4) the similar 

 forms in the salivary glands. I feel it incumbent 

 upon me to state that in my opinion the encapsuled 

 forms are merely resting stages of rounded or crithi- 

 dial forms, the interpretation of which as zygotes is 

 a pure assumption, and that the so-called schizogony- 

 forms have nothing at all to do with the life-cycle of 

 Schizotrypanum, but appear to be merely parasitic 

 organisms of the nature of yeasts from the intestine 

 of the insect. In justice to the author, however, it 

 should be mentioned that he does not regard his 

 observations on the life-cycle in the invertebrate as in 

 anv way final, and considers that many points remain 

 to be further investigated. 



The memoir of Chagas contains a great number of 

 very interesting observations to which space does not 



Fig. 3.— a->. Phase; oi Schizottypanuiii crtiziXn the bug, Concyhtmis megistus. 

 I, forms tr.insitional from the ordinary trypanosomes to the rounded forms 

 of rounded forms ; c andyi change of rounded into crithidial forms ; ^ and /( 

 lorms ; /, trypaniform type from the salivary glands ; j, encapsuled form froir 



permit of further reference. We may direct attention 1 

 especially to his experiments on the variations in the 

 virulence of the parasite as the result of passage 

 through different vertebrate hosts. The whole work 

 is an exceedingly important contribution to our know- 

 ledge of the trypanosomes, and we desire to con- 

 gratulate both the author and the Instituto Oswaldo 

 Cruz on a great achievement. E. A. Minchin. 



TIDAL RESEARCHES.^ 

 'T^IIE collection of data as to high and low water 

 -•- at various ports and the investigation of tidal cur- 

 rents present arduous tasks, and amongst those who 

 have devoted themselves to these subjects Dr. J. P. 

 van der Stok occupies a distinguished position. It 

 is due to him that our knowledge of the tides of the 

 Dutch East Indies rivals that furnished by our own 



' " Elementaire Theorie derGetijden— Getij-Constanten in den Indische n 

 Archipel." (K. Nederlandsch Meteorolngisch Instiluut, No. 102, 1910.) 



NO. 2127, VOL 



84] 



admirable survey of India. He is an ardent adherent 

 of the harmonic notation, and in the paper of which 

 we now give an account he tabulates the principal 

 tidal constants for no fewer than 138 ports in the Dutch 

 Indies. To the best of my belief this immense mass 

 of data has been collected and reduced through his own 

 personal initiative. 



This pamphlet gives an account of the theory on 

 which harmonic analysis is based, but it is to be re- 

 gretted, at least by all but his own fellow-countrymen, 

 that it should have been written in his own language. 

 Of course, the language is immaterial as regards the 

 tables of constants, but it may prove an obstacle to 

 those who desire to understand the other interesting 

 points treated by the author. 



Dr. van der Stok summarises his results in the 

 form of co-tidal charts for the tract of ocean extending 

 from the Malay Peninsula to New Guinea. The first 

 of these exhibits the march of the principal lunar 

 semidiurnal tide M,. It appears that there is a point 

 towards the south-eastern end of Sumatra 

 at which the wave divides, one portion travel- 

 ling north-west and the other eastward along 

 the south coast of Java. Along the north- 

 eastern coast of Sumatra, past Singapore, 

 the wave travels in the opposite direction, 

 namely, towards the south-east. It fs met 

 by a wave which travels westward and 

 south-westward along the southern and 

 northern coasts of Borneo, and westward 

 along the northern coast of Java. Thus, in 

 contrast with the divergence of the tide- 

 wave off the south of Sumatra, there is a 

 convergence from all sides towards a point 

 midway between Sumatra and Borneo. 

 Eastward of Borneo, in the direction of New 

 Guinea, the general trend of the wave is 

 northward. 



The second of these co-tidal charts is, I 

 believe, unique in that it exhibits the pro- 

 gress of the diurnal tide K,.' The path of 

 this wave exhibits a considerable re- 

 semblance to that pursued by the semi- 

 diurnal wave, but it differs in the fact that 

 it seems to approach the south coast of Java 

 from the south, and thus the line of advance 

 is from the south throughout the whole tract 

 extending from the southern extremity of 

 ,• Sumatra to New Guinea. 



I do not think that any previous investi- 

 <i, f and gator has attempted to draw a diurnal co- 

 '^■•h'i'^V tidal, chart. In the north Atlantic the 

 intestine, diurnal tide is insignificant in amount and 

 1 imperfectly known, but I think it might be 

 possible to construct a similar chart for the coasts of 

 India; I am not aware, however, that any such 

 attempt has ever been made. 



.\t the present time there are only three tide-pre- 

 dicting instruments in existence, namely, those in 

 England, France, and the United States; but I have 

 reason to know that a fourth is being constructed 

 for another Government. Without the aid of such an 

 instrument, tidal prediction is notoriously very labori- 

 ous, and any process which may render predictions 

 easier is very welcome. I have myself shown how 

 numerical predictions may be made, but the prelimJn- 

 ary computations are very laborious and tedious, 

 although when the requisite tables are once formed it 

 is easy and short to make a prediction.- But this 

 method does little to facilitate the computation of a 

 tide curve for a given place and given day direct from 

 the harmonic constants. Now Dr. van der Stok pro- 



1 There is a short discussion of the diurnal tides in Harris's " Manual of 

 Tide ," pa-t iv. A, p. 660. 

 - Phil. Trans., cl.\x.xii. A, p. 169, or vol. i. of my "Scientific P.ipers." 



