the excretory system of the stick insect, dixippus morosus

The excretory system of the stick insect 187
deep, but with very fine striations and a very indefinite inner margin. Towards the
middle region the diameter decreases to about ioo/x, the brush border becomes
a little less deep and the striations (filaments) are clearer and all of the same length
which defines the inner margin, although no surface can be brought to focus
(Fig. 36). The diameter of the distal region is about 8o/i. Over the last 2 or 3 mm.
at the tip the character of the border changes. The filaments are shorter and
gathered into clumps, rather in the way that the hairs of an animal's fur are held
together by surface tension when wet, and the inner margin can be brought to
focus (Fig. 3 a).
• • • • ' • ' • • - ' • ' • • • • • < $ • ( •
25/i Basement membrane
Fig. 3. Walls of Malpighian tubules. From living material, (a) Superior tubule, distal region,
showing change in brush border near the tip (left); in serum, (b) Superior tubule, middle
region; in serum, (c) 'Appendix of midgut'; in serum. (