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; 
