RURAL ENGINEERING. 1087 



tin' prevention oi union between tbe throe essential factors — the reservoir, the 

 transuiittiiif: ayent, and the receiitive host, a combination of anj' two to the 

 :iliS(iliUe cxclusifiii of tlio third beinj; harmless. 



Concerning' certain parasitic protozoa observed in Africa, J. E. Button, 

 J. L. Toni), and E. N. Tobky {I't. 1, Lircrpool t^chool I'l-op. Med. Mem. 21. 

 1906, pp. 87-97, pis. 2, fig. 1; pt. 2, Ann, Trop. Med. and Par.. 1 (1907), No. 3, 

 lip. 287-370, pis. 13, figs. 35). — Protozoal parasites of mannnals, birds, reptiles, 

 amphibians, fishes, and ai-thropods are bore considered. 



On some parasites in the museum of the school of tropical medicine, Liv- 

 erpool, A. Looss {Ann. Trop. Med. and Par., 1 {1907), Xo. 1, pp. l23-lo.'i, pis. 

 3). — Eifiht species of endoi)arasites, one of which is new, are considered in 

 this account. 



The presence of Spirochaeta duttoni in the ova of Ornithodoros moubata, 

 It. M. Carter {Ann. Trop. Med. and Par., 1 {1907), Ao. 1, pp. 157-160, pi. 1).— 

 The author concludes that ticks infected by spirochetes lay infected eggs, that 

 nuiJtiplication of the spirochetes probably takes place in the eggs, and that 

 iiiorpholoixical changes in the spirochetes also occur in the ejrgs. 



On the naorphology and life history of Spirochaeta duttoni. A. Breinl {Ann. 

 Trop. Med. and Par., t {1907), A'o. J, pp. //,i,5--'/38. pi. i).— "The life history of 

 I he spirochete might be thus summarized: Just before the crisis the spirochetes 

 disintegrate, certain of them coiling up into skeins, the majority of which are 

 phagocytosed by the spleen. Some of them become encysted and break up into 

 very small bodies, out of which the new generation of spirochetes is evolved." 



Contribution to the study of the Porocephalus moniliformis, A. Broden 

 and .J. lioDiiAix {Ann. Trop. Med. and Par., 1 {1908), No. ',, pp. .',93-50J,, pi. 1).— 

 observations on the occurrence of this parasite at Leopoldville, in Kongo Free 

 State, are here reported. A description is presented of the larvae. 



RURAL ENGINEERING. 



Irrigation in the Sacramento Valley, California. S. Fortier et al. {U. S. 

 Drpt Agr., Office E.rpt. ^tas. Bill. 207, pp. 99. pi. 1, figs. 2)).— The investigations 

 reported in this bulletin include a study of the present status of irrigation in the 

 Sacramento A'alley, its advantages, possibilities, methods, and costs. That this 

 \alley has not shared in the wonderful development which has taken place in 

 nther fertile valleys of the arid region is believed to be due largely to two condi- 

 Uon.s which have retarded the introduction of irrigation. First, that the climate 

 permits grain and hay to be grown in the winter months and matured in the 

 spring; and second, that the size of the majority of holdings is largo. In 1907 

 less than 1 per cent of the arable land was irrigated. 



Itegarding the general dovolopmont of the valley through irrigation, the 

 authors believe that three operations are involved, namely : (1 ) Protective works 

 to control floods, estimated to cost $24,000,000; (2) providing a water supply for 

 irrigation, .$.".0,000,000; and fS) preparing the land for irrigation. $.3.5.000,000. 

 In this connection the introductory chapter of the bulletin gives a review of the 

 present agricultural situation, in which are discus.sed early efforts at develop- 

 ment, soil, climate, overflow conditions, etc., and the general status of irriga- 

 tion development. 



The method ffillowed in the investigations was to make detailed studies of 

 representative localities and general observations of the remainder of the terri- 

 tory. The localities selected were the lands irrigated under the Yolo County 

 <'onsolidated Water System, Yolo County, under the Central Canal in fJlenn and 

 Coluso eounties, under the P.utte County Canal In P.utte and Sutter countie.s, 



S.'30TO— Xo. 11— OU 7 



