the Academy of Sciences at Haarlem. 449 



ously been difficult to explain, such as quartz, and other very- 

 hard minerals : and considering that the knowledge of all the 

 circumstances which concur in the crystalline formation of 

 minerals, may serve to explain many points in geology ; it is 

 enquired, What are the observations and experiments which 

 demonstrate the influence of Electricity, Magnetism, Heat, 

 and Light, upon the crystallization of quartz and other mine- 

 rals insoluble in water ; and by which, at the same time, we 

 may be made acquainted with the other circumstances favor- 

 able to crystallization ? The Society is desirous that this 

 subject should be explained by fresh experiments. 



IX. — The supposition of a spontaneous generation of In- 

 fusoria, and other small animals, having been considerably 

 checked, and in part refuted, by the numerous and important 

 observations of Professor Ehrenberg, relating to the organiza- 

 tion and reproduction of Infusoria; the Society proposes 

 this question. What are the animals formerly supposed to 

 multiply without fecundation, but the propagation of which 

 by sexual intercourse is now sufficiently established ? Which 

 on the contrary, are the animals, whose production, not pre- 

 ceded by fecundation, we must still admit ? Above all, what 

 notion may we form, in the present state of Zoology, of the 

 origin of intestinal animals ? 



X. — How far are we acquainted with, or ought we to ad- 

 mit, those physical forces which M. Dutrochet believes him- 

 self to have discovered, and which he points out by the names 

 of "Endosmose et Exosmose," in his work entitled 'L'agent 

 immediat du mouvement vital, devoile dans la nature et dans 

 sa mode d'action, chez les vegetaux et chez les animaux.' — 

 Paris: 1826? See also, 'Annales de Chimie et de Physique,' 

 vol. xxxv. p. 393 ; and vol. xxvii. The Society is desirous 

 to see this subject cleared up as much as possible by fresh 

 researches. 



XI. — It has been frequently observed among some living 

 plants, that in certain cases they emit a phosphoric light ; as 

 for instance, the Tropceolum, Calendula, Lilium bulbiferum, 

 Tagetes, Euphorbia phosphorea, Rhizomorpha, Sac. ; and the 

 Society requests, That by researches made for this express 

 purpose, it should be endeavoured to elucidate this pheno- 

 menon ; to ascertain how far what has been stated concerning 

 it is admissible as fact ; and what are the circumstances un- 

 der which it takes place, as well as what is the cause of it. 

 Vide 'Acta Suecica,' 1762 and 1768. Ingenhouz, 'Ver- 

 suche mitPflanzen,' 79; 151. Nees V. Esenbeck & Bischof; 

 ' Nov. Act. Leop. Car. 11/ 605. L. C. Treviranus, < Zitschr. 



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