ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 35 



accompany them throughout their course. These the author calls 

 " nuclei of the plexus " (noyaux de I'arhorisation), comparing them to 

 those so named in the Vertebrata. 



In Tipula there is attached to the principal branches of the plexus 

 a granular substance provided with special nuclei, which must be 

 compared to the " fundamental nuclei " and " granular substances " of 

 the plexus of the higher Vertebrata. They are completely wanting 

 in Stratiomys. 



Between the plexus of Stratiomys and Tipula there exists a differ- 

 ence analogous to that observable between the plexus of the frog and 

 that of the lizard. 



These results do not necessarily invalidate, the author says, those 

 of Eanvier and Foettinger, because he has dealt with a histologically 

 different matter. They confirm, however, the observations of Eouget, 

 who has described the axis-cylinder as forking in the interior of the 

 cone, the two branches of the fork being applied to the surface of the 

 contractile mass but not appearing to extend further. They also 

 confirm his view that the granular matter which fills the cone is of 

 little importance, being absent in Stratiomys. 



Wings of Insects.* — Dr. G. E. Adolph figures a large number 

 of wings chiefly of Hymenoptera, and points out that the arrange- 

 ment of the concave and convex lines is the most constant character, 

 but that the concave are much more persistent than the convex. A 

 study of the arrangements seen in Vaiiessa has shown him that the 

 tracheal system of the wing is first developed along certain primary 

 lines, the most primitive and striking peculiarity of which is their 

 tracheal nature ; between these there are developed certain costal 

 elements. After dealing with the Lepidoptera he passes to the 

 Diptera, and in their case, as in that of the Neuroptera, he institutes a 

 comparison with the Hymenoptera, pointing out how fresh branches 

 become developed and earlier nervules absorbed. 



In a second paper f he deals with certain abnormal developments 

 in the wings of some Hymenoptera. 



Structure of the Proboscis of Lepidoptera.| — W. Breitenbach, 

 dealing with the phylogeny of this organ, finds in the early stages of 

 the insect indications of its origin, for in the late larva it has been 

 found already represented by two long curved cords. But further, the 

 obvious connections of the group with the Trichoptera show that the 

 biting mouth of the latter has produced the sucking tube of the former 

 by modification of the labium, maxillae, and labrum, which were at 

 first all united into a tubular organ ; the edges of the two maxillfe 

 then became more closely approximated, and the share of the other 

 two parts in the organ became unnecessary, and they were excluded 

 from it. This metamorphosis, however, was probably made in various 

 stages, each having some definite advantage to the insect as its object : 

 e. g. the exclusion of the labrum and labium from the organ was a 



* Nova Acta Acad. Cses. Leop.-Carol. Germ. Nat. Cur., xli. ii. (1880) pp. 213- 

 92 (6 pis.). 



t Tom. cit. pp. 293-328 (1 pi.). 



X Jenaisch. Zeitschr. Nat., xv. (1881) pp. 151-214 (3 pis.). 



D 2 



