382 HAL DOWNEY 



composed largely of straight, stiff, coarse fibers which are so 

 numerous that little remains of the original hypodermal cell 

 except the nucleus, and cell limits are entirely obliterated. 



A basement membrane or connective tissue ' Grenzlamella ' 

 between the hypodermal cells and the muscle fibrils, at the point 

 of muscle insertion, is described by Claus, McMurrich, van Rees, 

 Schneider, Holmgren and many other authors. Lecaillon, Sneth- 

 lage and Riley also describe a basement membrane for the hypo- 

 dermal cells, but in the region of muscle attachment it bends 

 around and becomes continuous with the sarcolemma, and there- 

 fore it does not extend between the epithelium and the muscles. 

 Claus states that it is a cuticular formation in Branchipus and 

 Artemia, and that it may become chitinous. In some regions 

 it is absent. In the Decapods, however, it is a true connective 

 tissue 'Grenzlamella. ' McMurrich and Holmgren also claim that 

 it is merely a cuticular membrane formed by the epithelium, the 

 former describing thickenings of the membrane (in terrestrial 

 Isopods) at the cell boundaries from which supporting fibers 

 originate and pass up into the cells, van Rees published figures 

 which show that in Musca vomitoria the basement membrane 

 is formed from long processes of the hypodermal cells which sur- 

 round the muscle insertion. According to Emmel the first base- 

 ment membrane in the regenerating claw of the lobster is a 

 homogeneous cuticular formation of the ectodermal cells. A nu- 

 cleated membrane is formed later, the origin of which Emmel 

 was unable to determine. The intermediate membrane is of con- 

 nective tissue origin according to Schneider, and Claus states 

 that it is a connective tissue formation in the Decapods. 



Claus found the basement membrane to be absent from some 

 regions of Branchipus and Artemia, and Henneguy never saw 

 it in the Insecta and claims that it is not present in other Arthro- 

 pods, but that the Z lines of the muscle fibers give the appearance 

 of a basement membrane. There is no basement or intermediate 

 membrane in the Millipedes according to Duboscq. Snethlage 

 finds no intermediate membrane at the point of insertion, but 

 pigment granules and anastomosing muscle fibrils give the appear- 

 ance of a basement membrane. 



