ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 745 



method. Hardening with 1 per cent, superosmic acid was also resorted to. 

 Haematoxylin alone, or in aqueous solution with potassium chromate, and 

 gentian-violet were successfully used for staining. 



"When the hind leg and thorax of Dyiiscus marginalis, for instance, are 

 opened, the muscles in the former are seen to be beautifully white, while 

 those of the thorax have a yellow, almost brownish colour. After removing 

 the ventral wall and viscera, two conical white muscles are seen to spring 

 from the dorsal portion of the posterior segment of the thorax and to have 

 their apex inserted on the hind pair of legs. These are the white hip- 

 muscles (Hiiftmuskeln) which work the last pair of legs in and out. When 

 these are removed, there are seen in front the yellowish-brown muscles 

 which pass as strong beams between dorsal and ventral surfaces, and belong 

 to the mechanism of flight. 



I. The muscles of flight (in Oryctes nasicomis, &g.) are (a) very soft, and 

 break up most readily into bundles of fibrils, which are surrounded by an 

 extremely abundant intermediate substance of a somewhat fatty nature with 

 " interstitial granules," probably v^ith a nutritive function, (h ) The bundles 

 of fibrils are not only surrounded by very abundant tracheae, but these pene- 

 trate into the bundles, and form fine ramifications round the several groups, 

 (c) These fibril bundles exhibit no sarcolemma nor nuclei, and thus differ 

 markedly from the muscle-fibres of Vertebrates. The probably rich nutritive 

 supply afforded by the abundant interstitial substance, and the most efficient 

 oxidation secured by the ramification of the tracheae, are in obvious 

 association with the high degree of activity of the wing-muscles. It is 

 interesting that in the pulmonate spiders there are muscles very similar 

 to the yellow thoracic muscles of insects, but differing in these important 

 points : they include no tracheae, the cementing intermediate substance is 

 less copious, the transverse sections of the fibrils are much smaller, the 

 fibrils are nucleated and apparently possess a sarcolemma. 



II. The muscles of the legs. — Each of the muscle-fibres may be compared 

 to a cylinder with an axial strand of non-contractile substance which is 

 continued on all sides into extremely thin longitudinal plates, radially 

 disposed, and extending to the wall of the cylinder. The distance 

 between each two of these cementing interstitial substance plates is equal 

 to the diameter of the primitive fibrils which occupy the intervening spaces 

 in radially disposed rows. Corresponding to each of the transverse stripes 

 the cementing plates bear ridge-like thickenings, which, in total contraction, 

 appear as rows of sj)ots, while the intermediate substance appears as fine 

 longitudinal connecting lines. This is in marked opposition to Eetzius's 

 description of the central protoplasmic mass as a row of cells from which 

 fine processes radiate out on all sides, at equal distances and in parallel 

 planes. This the author entirely disagrees with. Deviations of detail in 

 other insects are noted. Herr v. Limbeck refers in a postscript to an 

 overlooked note by Eollet in the 1884 volume of the same Transactions as 

 that in which his own paper appears. This note refers to the above 

 differences between thoracic and leg muscles. 



Halobates.* — From his investigations into the structure of Halobates, 

 Dr. E. Witlaczil is inclined to difter from the view of Mr. Buchanan White 

 who regards the genus as representing a very primitive form ; Dr. Witlaczil 

 bases his objection on the fact that Halvhates agrees in its internal structure 

 with other Hemiptera, so that it must be regarded not as a trunk-form, but 

 as a type a good deal altered by adaptation to its life in water ; thus it 

 has lost its wings, and the development of the musculature which serves 



* Zool. Anzeig., x. (18S7) pp. 336-9. 



