ZOOLOGY AND BOTANY, MIOKOSOOPY, ETC. 45 



tlie least owing to tlie development of a high instinct in the bees, hut 

 simply to physical laws dependent upon the position assumed by the 

 workers and to the shape of their body and the plasticity of the wax. 

 The cells of the comb are in reality circular, and in those species of 

 wasps and bees which form but a single cell remain circular ; the pris- 

 matic shape of the cells of a complex honeycomb is simply owing to 

 the mutual pressure of the adjacent cells and is strictly analogous to the 

 formation of cylindrical prismatic soap-bubbles by mutual pressure. 



We remember to have seen this explanation before, though we 

 cannot now fix the reference. 



Mouth-Organs of Rhynchota.* — 0. Geise regards the flattened or 

 more or less curved process of the clypeus of the Rhynchota as the 

 homologue of the labrum of beetles ; the jointed groove corresponds 

 to the labium, the two separable sette to the mandibles, and the two, 

 only with difficulty separable, setae to the maxillae of biting insects. 

 He next considers the structure which Savigny regarded as the ligula, 

 but to which most authors have applied Burmeister's name of 

 " Wanzenplatte " ; he himself proposes to speak of it as the pharynx, 

 and describes it as being endowed with great elasticity, and as acting 

 as a pump, which is set in action by the contraction of muscles 

 attached to the body-wall, whereby the space in the walls in which 

 they are inserted is enlarged, and a vacuum thereby formed. The 

 structure and relations of these parts are entered into in great detail, 

 but a full abstract of the paper would be impossible without a repub- 

 lication of the figures to which constant reference is made. The essay 

 should receive the careful study of students of the anatomy of insects. 



Development of Genital Organs of Insects. f — A. Schneider is here 

 reported as concluding that a muscular fibre from the heart serves as 

 the point of origin of the genital organs of insects ; this may be best 

 demonstrated by the larva of Coretlia plumicornis, where a fibre belong- 

 ing to the alcB cordis gives off a branch which passes backwards and ends 

 at the intestine ; a little way from its origin this fibre swells out and 

 becomes provided with a large number of nuclei ; at a later stage 

 these nuclei may be seen to belong to two sets differing in size ; the 

 largest are surrounded by a layer of protoplasm and become the in- 

 dependent cells of the " primitive ova." 



In the viviparous Cecidomyice there are ova which, like those of 

 other insects, segment and undergo further development ; these are 

 never found in the ovarian sacs. In the rest of the Diptera and in all 

 other insects the primitive ova give rise to ovarian culs-de-sac. In the 

 Culicidae each primitive ovum gives rise to a sac in which only one 

 definite egg is found. 



When a primitive ovum is transformed into an ovarian sac, the 

 nucleus divides, one half becomes much larger and goes to form the 

 nucleus of the egg, while the smaller undergoes division and forms a 

 kind of follicle ; some of the small nuclei increase in size and become 

 eggs, and in this way moniliform sacs are formed. 



* Arch. f. Naturg., xlix. (1883) pp. 315-73 (1 pi.), 

 t Arch. Zool. Expe'r. et Gen., i. (1883) p. xlvii. 



