1908] Muscle Attachment in Insects 267 



longitudinally striate but their fibrils appear finer than those of 

 the muscle and there is no clear evidence of direct continuity of 

 the two. On the contrary, I believe that there occurs a splicing 

 or fusion of the two types of fibrils, the basement membrane being 

 lacking at the point of contact. 



The sections first studied were of alcoholic material, cut at 

 io,« and stained in haematoxylin and eosin. In order to make 

 a more careful study material was fixed in Flemming's and in 

 Gilson's fluids, sectioned at 2-^/1 and stained in iron haematoxylin. 

 The appearance was then very similar to that presented by the 

 above mentioned sections of Chortophaga. 



As may be seen from figure 3, the striae are much more 

 prominent and the muscle fibrils, as in Chortophaga, are appar- 

 ently continued through^ the body of the hypodermal cells to 

 attach directly to the cuticula. This appearance is greatly 

 emphasized in the sections in which, as in figure 4, the cuticular 

 layer has been torn away. Then the distal ends of the cells 

 present a frayed-out appearance, due to the projecting fibrils. 



At the Chicago meeting of the American Association I exhi- 

 bited lantern slides from these preparations and, emphasizing as 

 they do, the appearances found by Snethlage in a large series of 

 insects, I believed that they represented direct attachment of the 

 muscle fibers to the cuticula. Studies of developing muscle in 

 the postembryonic stages, and renewed examinations of the 

 conditions in Anax and other forms have forced me to return 

 to my first interpretation of the conditions. 



Most instructive were sections through the developing wing- 

 muscles of Anax such as represented by figures 5 and 6. In 

 these photographs there is to be seen an apodeme-like invagi- 

 nation of the body-wall, surrounded by its hypodermal cells. 

 Near its apex these cells become suddenly greatly elongated, 

 their nuclei become fusiform, and placed at the bases of the cells, 

 while prominent longitudinal striae appear within them. The 

 basement membrane is defiected to enclose the muscle fibers and, 

 in fact, the whole appearance seems to support Snethlage' s 

 contention that the muscle fibers are hypodermal in origin, 

 merely prolongations of the epithelial cells. 



From my studies I am, however, unable to accept this view 

 that the muscle fibers of the arthropods are structurally prolong- 

 ations of the chitinogenous cells. Snethlage bases his theory on 

 a study of the development of the musculature of the nauplii of 



