July 20, 1883.] 



SCIENCE. 



the total kinetic energy, the process of ex- 

 change by radiation is, on the whole, slow. 

 Were, however, the translatory motion the 

 direct cause of radiation, the exchanges be- 

 tween diathermous bodies must apparently be 

 nearly instantaneous. 



( To be continued.) 



OYSTER-CULTURE IN HOLLAND. 



The first ot a series of papers on the European 

 oyster and oyster industry of the Eastern Schelde ' 

 has just been published by Mr. P. P. C. Iloek, secre- 

 tary of the commission of the zoological station of 

 the zoological society of Holland. It is to be fol- 

 lowed by a series of papei-s gotten up in similar style 

 by eminent specialists: 1°. On the embryology of the 

 European oyster; 2°. On its food, parasites, and com- 

 mensals; 3°. A review of the fauna of the Eastern 

 Schelde; 4°. A report on the physical conditions pre- 

 sented by the Eastern Schelde; '>°. A report on ex- 

 periments made to determine the conditions under 

 which the fixation of the larval oyster occurs. 



In this report the author devotes a short chapter 

 to a discussion of the classical allusions to the animal, 

 from the Homeric period to the liuie of Oppian. Then 

 comes a chapter on the references to the oyster found 

 in Conrad Gesner's Uintoria animaliMm, lib. iv., 

 edition of KiiiO; followed by an exhaustive bibliog- 

 raphy of ninety pages, in which the works of up- 

 wards of two hundred aiul seventy-five authors are 

 mentioned, covering the period from 1GS5 to 1883, or 

 nearly two hundred years. 



Then follows a paper on the organs of generation 

 of the oyster, by Mr. Hoek, accompanied by an 

 excellent series of lithographic plates representing 

 microscopic transverse sections of the European 

 oyster. The text of this is in Dutch and French on 

 alternate pages. A chapter is devoted to a historical 

 re.iwmc of our knowledge of the anatomy of the gen- 

 erative organs, and is succeeded by an account of the 

 author's iuwjstigations. 



A second part is devoted to the physiology of re- 

 production, and is preceded by an historical sketch of 

 this part of the subject, fio«n the time of Leeuen- 

 hodv to the present. The author gives a summary 

 of his results, both anatomical and physiological, a.s 

 follows: the genital gland is not a compact organ: 

 it lies on the surface of the body of the animal under 

 a thin layerof connective tissue (mantle), below which 

 branched ducts spread out over the reproductive 

 organ, connected on the innerside with the reproduc- 

 tive follicles, Which have a generally vertical direction 

 to the surface of the visceral mass, and which anas- 

 tomiise with each other. The generative products 

 develop on the walls of the follicles, the ova and 

 spermatozoa being formed side by side. The author 



* Vernlag omtrent onderzoekingen op de oetlgr en de oenter- 

 culluur betrrkklng hebbende. .[/letiering i. (Willi title In 

 Fr«icb : liapport 9ur tfs rec/iercfie» concerntint Vhttitre et 

 I'ottriicultare. Liuraiton i.) Lcldcn, E. J. Brill, 1883. 253 

 p., 5 lUbogmpbic platea. 8". 



inclines Co the belief that the generative products are 

 developed from the ectoderm. The ova are devel- 

 oped from single epithelial cells adherent to the wall 

 of the parent follicle, while the mother-cells of the 

 characteristic masses ot spermatozoa are only por- 

 tions of such cells. The organ of Bojanus does not 

 have a compact structure as in other lamellibranchs, 

 but is com|)osed of a mass of ducts and blind sacs, 

 which forms a thin flat plate of considerable extent. 

 Contrary to what may be noted of the reproductive 

 glands, the organ of Bojanus extends somewhat into 

 the mantle. The ducts and cavities of the organ of 

 Bojanus pour their contents into a longitudinal cav- 

 ity, — the urinary chamber, — the walls of which are 

 also excretory in function, and open outwardly by 

 way of a short urinary canal. The external orifice 

 of the renal organ opens into the same cleft as the 

 genital duct, a little behind the latter, but they do 

 not actually join. These genito-uiinary sinuses lie 

 below the adductor on either side of the ventral pro- 

 cess of the body-mass. A reno-pericardiac canal 

 connects the urinary chamber with the pericardiac 

 cavity. It is probable that the auricles of the heart 

 also exercise an excretory function. 



An oyster which has fry in the branchiae is the 

 parent of the same. At the moment of emission 

 from the ovaries, not only have the ova been ferti- 

 lized, but they have also passed through the first 

 stages of segmentation. The sperm necessary for 

 fecundation does not come from the same parent. 

 The water which flows over other oysters in the vi- 

 cinity charged with sperm, which they have set free, 

 is carried into the mantle-cavity of egg-bearing in- 

 dividuals, and into their genital ducts and their 

 branches. The oysters of the Eastern Schelde are 

 two years old before they have brood ; they are most 

 prolific at the age of four or five years. There are 

 more sperm-bearing oysters in the Eastern Schelde 

 than egg-bearing ones. All of the mature eggs are 

 laid at once; the production of sperm is probably 

 continued for a longer time. In every instance that 

 was investigated, the production and emission of ova 

 is followed by a period during which no sperm is pro- 

 duced. A large proportion of the spat fouml fi.Ked 

 on the banks in the Eastern Schelde was probably 

 not derived from the oysters inhabiting the culti- 

 vated beds. Culture appears to act injuriously upon 

 the reproductive powers of the animal. In old oys- 

 ters the liver is much more developed than in younger 

 ones. This greater development of the liver is de- 

 pendent upon the less marked development of the 

 reproductive organs. J. A. Kyder. 



GALTON'S HUMAN FACULTY. 



Inquiries into human /aculli/ ami itn development. 

 By FitAXCis Galtox. F.R.S. New York, Mac- 

 7m7/«n, 1883 12 -|- 380 p., 6 pi. 8°. 



Mr. G.vlton's researches have for a good 

 while attracted the attention of Kiiglish and 

 American students of psychology and anthro- 

 polog}-. As the^' are here brought together, 



