88 MCMURRICH. [VoL. XIV. 
in which case there is generally a thickening of the basement 
membrane at their point of origin. From the thickenings of 
the basement membrane, which occur opposite the lines of junc- 
tion of adjacent cells, numerous fibres always arise. At their 
origin the fibres are of considerable strength, but as they pass 
towards the cuticle they split lengthwise and finally fray out 
into fine fibrils which are attached to the under surface of the 
cuticle. These final portions of the fibrils do not hold the stain 
as do the fibres proper and their larger branches, but resemble 
in this respect the lower layer of the chitinous membrane with 
which they are connected. 
In very young specimens of Porcellio and Armadillidium, no 
trace of the supporting fibres could be discovered, and in a 
specimen of Oxzscus measuring 4 mm. in length they were but 
slightly developed, projecting into the cytoplasm from the base- 
ment membrane but a short distance (Fig. 11, sf). Prepara- 
tions from the “‘midgut’”’ of adult specimens of /dotea robusta 
showed practically the same conditions as the 4 mm. specimens 
of Onzscus. 
As I have pointed out, the behavior of the fibres to iron-lack 
hematoxylin indicates for them a different chemical composi- 
tion from the cytoplasm, and it is to be noted that it also indi- 
cates for them a similarity to the basement membrane from 
which they arise. Their terminal fibrils, however, appear to 
partake rather of the character of the chitinous membrane, but 
it is presumable that they are altogether products of the cyto- 
plasm, and not, as Ide supposes, simply thickened portions of 
the cytoplasmic reticulum. A confirmation of this idea, derived 
from their chemical behavior, is furnished by a_ physical 
character which they possess, namely, brz¢tleness. Sections 
frequently cut the fibres at an angle, and in such cases they 
are often broken across, the lines of fracture being clean and 
distinct, as is shown in Fig. 5, sf’. This brittleness is probably 
the result in part of the reagents used in imbedding, but it is 
a character quite foreign to protoplasm when similarly treated, 
and one frequently observable in chitinous and certain sup- 
portive substances, such as, for instance, the mesogloea of some 
Ccelentera. 
