ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 505 



nuclei of some cells in the midgut of Oryctes. The median ventral 

 groove of the midgut in the larvte of Oryctes, Cetonia, and Tropinota is 

 a sort of glauduhxr caecum with a digestive secretion. The sac which 

 forms the median portion of the proctodfeum is the absorptive part of the 

 intestine in these larvae. 



Bees and Flowers.* — Dr. M. Kronfeld corroborates the old observa- 

 tion, which even Aristotle recorded, that bees do not fly at random from 

 one flower to another, but for a longer or shorter period restrict their 

 visits to one species. Three times before a bed of Cucumis the observer 

 detained a bee, and watched it return when liberated to the same kind 

 of flower though others were there in abundance. At a bed including 

 eight difl'erent kinels of flowers the bees were apparently blind to all but 

 one species. In a meadow with abunelance of inviting flowers, repre- 

 senting nearly a score of species, Herr Kronfeld saw a humble-bee 

 visit within ten minutes twenty-eight heads of goat's-beard, and no 

 others. The observations, therefore, show a considerable degree of 

 constancy in the bees' visits. 



Stigmata of Hymenoptera.f — M. G. Carlet finds that the stigmata 

 of the Hymenoptera are always open, and that there is not the least trace, 

 at their orifice, of any obturator apparatus. They are of extremely 

 small size, and have, consequently, received but little attention ; more- 

 over they are generally covered externally by hairs which are often 

 ramose, and which serve to prevent the introduction of foreign bodies, 

 even in the form of fine dust. The tracheal trunks may be opened or 

 closed at the will of the insect ; this mode of closure, which the author 

 calls opercular, is effected by means of a special tracheal muscle which is 

 inserted in the trachea, above a cleft which is found on it in front of 

 the stigma ; the tracheal muscle raises the upper lip of this cleft, 

 that is to say the operculum, in the mode of the lid of a snuff-box. 

 The difficulty of the investigation to which M. Carlet has lately devoted 

 himself may be estimateel from the fact that this muscle is more delicate 

 than the finest silk-thread of commerce. 



Development in Egg of Musca vomitoria.|— Dr. A. Voeltzkow 

 has published a full account of his researches on this subject. To our 

 notice of his preliminary communication § we may now add the follow- 

 ing. The Malpighian vessels are formed as evaginations of the hind-gut, 

 and the sucking stomach as an evagination of the fore-gut. The salivary 

 glands are formed by invagination of the ectoderm in the anterior part 

 of the head and are laid down separately; later on they open by a 

 common efferent duct into the mouth. The ventral cord, when fully 

 developed, consists of two longitudinal cords of nerve-fibres which are 

 inclosed by nerve-cells ; in correspondence with each segment the nerve- 

 cells are separated by a ventral mass of cells. The longitudinal trunks 

 lie close to one another, but do not fuse, being separated where they 

 touch by a fine layer of cells. In the course of its further development 

 the ventral cord shortens considerably ; the author does not agree with 

 Weissmann that the indications of the earlier segments are lost. He is 



* Biol. Centralbl., ix. (1889) pp. 28-30. 



t Comptes Ktiidus, cviii. (1889) pp. 862-3. 



I Arbeit. Zool.-Zoot. Inst. Wiirzburg, ix. (1889) pp. 1-48 (4 pis.). 



§ See this Jourual, 1888, p. 572. 



