MUSEUM OF COMPARATIVE ZOOLOGY. 69 



The views held by Schimkewitsch ('84, pp. 8, 9, 12) are widely at 

 variance with those of all tlie other writers. He is without doubt right 

 in bringing the " inner cuticula," the so-called "sclera," and the pre-retihal 

 membrane into a single category ; but misled, as I think, by appearances 

 of the sclera that can readily be explained in another manner, he has 

 concluded that all these structures are cellular.* 



Schimkewitsch finds that at the point of insertion of the dorso-ventral 

 muscles of the abdomen this " inner cuticula " is continuous with the 

 sarcolemma of the muscular bundles. Reasoning from Froriep's ('78) 

 conclusion that the sarcolemma of the striate muscles in vertebrates is to 

 be. regarded as connective tissue, he maintains that this internal cuticula 

 in Arthropods must also be regarded as a connective [-tissue] formation. 

 He reaffirms the fact stated by Graber ; viz., that this same cuticula is 

 prolonged in the form of a pre-retinal layer, and that it merges with the 

 envelope of the eye ("sclera"), — "although it tends to prove the chiti- 

 nous nature of this envelope ; hut,'" he adds, " nuclei are readily visible in 

 its thickness.'''' f Finally, in Lycosa saccata during development there 

 lies beneath the integument, directly under the chitinogeuous layer and 

 outside the future subcutaneous muscular layer, a series of very flat 

 cells ; and they represent, so he claims, the future " internal cuticula " of 

 Graber. 



Neither the nuclei in the thickness of the internal cuticula, nor the 

 conditions observed in the development of Lycosa, are figured, so that it 

 would be very difficult to judge of the value of Schimkewitsch's conclu- 

 sions, were it not that he has figured the same conditions, which recur 

 in the envelope of the eye (sclera). " I have already shown," he says 



* MacLeod ('80, pp. 31-34), it is true, has urged a similar proposition respecting 

 the so-called membrana externa, or m. propria of the tracheal tubes, as well as the 

 basement-membrane of the integument ; but his conclusion is based upon theoretical 

 considerations rather than upon satisfactory direct evidence. Until the demonstra- 

 tion in this membrane of nuclei distinct from those of the epithelial cells (chiti- 

 nogenous matrix) is possible, the question cannot be considered as settled in favor of 

 the connective-tissue nature of the membrana propria of the integument. 



Grenacher ('80, p. 26) has also spoken incidentally of the fact that the thin, inner 

 cuticula of the hypodermal cells in the larv* of Dytiscus are " stellenweise kerntra- 

 gende ;" but I do not understand that he directly commits himself to' the opinion 

 that these nuclei belong to cells which have served as the matrix of what he calls 

 *' Cuticula," much less to the opinion that this membrane is a cellular structure. 



t " La meme cuticule interne se prolonge en forme de lame preretinenne dans les 

 yeux et se confond avec I'enveloppe de I'ceil, comme I'a demontre Graber, et je puis 

 afifirmer le fait, bien qu'il tende h. prouver la nature chitineuse de cette enveloppe ; 

 mais des noyaux dans son epaisseur sont bien visibles" (p. 9). 



