292 ENTOMOLOGICAL NEWS. [June, '08 



Mexico City in September, 1906, and published in that place under date 

 of 1907, received in Philadelphia in March, 1908. M. Cayeux discusses 

 (in French, pp. 1223-1227), first, the geological portion of a communi- 

 cation of Virlet d'Aoust "on the eggs of insects serving as food for 

 man and giving rise to the formation of ooliths in the lacustrine 

 limestones of Mexico" (Compte Rendus, Acad. Sci. Paris, vol. 45, 

 p. 865, 1857). Then, on the basis of material furnished him by the 

 Mexican Geological Survey he concludes : It is undoubted that the 

 egg of an insect, entire or broken, is a centre of concentration for the 

 limestone of the lacustrine sediment and that it determines the forma- 

 tion of innumerable small, iregular nuclei, but in truth it does not form 

 an oolith properly so called in the Mexican lakes. The globules which 

 result from the molecular concentration of carbonate of lime around 

 the eggs have the morphological characters of ooliths. They possess, 

 when they are complete, a central voluminous nucleus, in which are to 

 be found all the elements of the lacustrine sediment, and a non-differen- 

 tiated thin and irregular cortical zone. In white light, one never 

 discerns concentric or radiate structure ; in polarized light, the ex- 

 tremities of a well-marked black cross are often observed. As they 

 are to-day, these globules constitute a new and highly interesting cate- 

 gory of false ooliths, that is corpuscles which to the naked eye are 

 not to be distinguished from true ooliths and which arise according 

 to the sedimentation either by partial crystallization of a limestone 

 sediment or by concentration of carbonate of lime around foreign 

 bodies. The false ooliths in process of formation in the neighbor- 

 hood of Mexico City are essentially different from ooliths with con- 

 centric structure so widespread in the primary and secondary rocks. 

 However, the lacustrine and brackish water deposits of the tertiary 

 may contain some elements of the same origin. The microscopic study 

 of this terrain is too little advanced to affirm that this category of 

 pseudo-ooliths is not represented there. 



[Neither M. Cayeux nor M. Virlet d'Aoust mention the species of 

 insect concerned. Perhaps the eggs are those of Corixa referred to 

 in many text books of entomology.] 



ANNOUNCEMENT. The Lake Laboratory, maintained by the Ohio 

 State University, announces the usual program for the coming sum- 

 mer, including courses in General Zoology and Botany, Entomology, 

 Ornithology, Experimental Zoology, Comparative Anatomy, Ecology, 

 Embryology, Invertebrate Morphology and Ichthyology also oppor- 

 tunities for research work and accommodations for investigators as 

 in previous years. The staff will include, besides the Director, Pro- 

 fessor E. L. Rice, of Ohio Wesleyan University; Professor Lynds 

 Jones, of Oberlin; Professor Charles Brookover, of Buchtel College; 



