92 MCMURRICH. [VoL. XIV. 
specimens, but is lost in the adults; a change which is probably 
correlative with decided alterations in the structure of the 
cytoplasm. 
The cytoplasm in young specimens has a uniform, finely 
reticulated structure (Fig. 11), but this is replaced in the adults 
by a much less uniform arrangement. In addition to the 
development of the supportive fibres which traverse it, the 
protoplasm has lost to a certain extent its reticular structure, 
becoming more granular; and, at the same time, vacuoles (Figs. 
4, 5, v) have developed in it in considerable numbers. Towards 
the outer and inner surfaces of the cells the reticulum is more 
apparent than elsewhere, but I have seen cells whose central 
parts were practically a single large vacuole, only the traversing 
fibres being surrounded by protoplasm. 
In all the land forms I have examined, the cytoplasm is for 
the most part in close contact with the under surface of the 
chitinous cuticle, but in nearly every surface preparation places 
can be found where there is a distinct space between the two, 
this space being, however, traversed by the supporting fibres 
and, apparently, also by strands of protoplasm. In surface 
views, with a high focus, these strands are seen passing on all 
sides to the folds of chitin between the domes of adjacent cells, 
and one gets an appearance as if there were intercellular 
bridges of protoplasm connecting the cells. This appearance 
vanishes, however, when the focus is set at a lower level, and 
sections (Fig. 5) demonstrate its true significance. In /dotea 
vobusta this structure was particularly evident (Fig. 6), being 
present in every cell, and here the strands traversing the space 
are probably protoplasmic alone, since the supporting fibres 
project up into the cytoplasm only a short distance from the 
basement membrane. 
In addition to the vacuoles which have already been men- 
tioned and which possess fluid contents which do not stain with 
the reagents employed, others of a different character occur in 
adult animals, though I have not found them as extensively 
developed in either Povcellio or Oniscus as in Armadillidium. 
In the last-named genus the vacuoles, which are characterized 
by containing a floccular stainable material, extend frequently 
