MUSEUM OF COMPARATIVE ZOOLOGY. 69 
The views held by Schimkewitsch (’84, pp. 8, 9, 12) are widely at 
variance with those of all the other writers. He is without doubt right © 
in bringing the “inner cuticula,” the so-called “sclera,” and the pre-retinal 
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 ; but,” he adds, “ nucler are readily visible in 
its thickness.” + Finally, in Lycosa saccata during development there 
lies beneath the integument, directly under the chitinogenous 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 Aas 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 larve 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. 
+ “La méme cuticule interne se prolonge en forme de lame prérétinenne dans les 
yeux et se confond avec l’enveloppe de l’ceil, comme l’a démontré Graber, et je puis 
affirmer le fait, bien qu’il tende 4 prouver la nature chitineuse de cette enveloppe ; 
mais des noyaux dans son épaisseur sont bien visibles” (p. 9). 
