In nature pipe is an essential elements for their existence. In human anatomy (plate 35A) pipe is one of most important components that allow carrying air, food, and blood flow to various other organic substances. Animal bone structure is hollow-pipe (plate 35B) that has the passage for flexible bone marrow. In insects use of hollow pipe is for sucking fluids (honey, blood, etc) for their survival. The butterfly’s mouth has the shape of a long hollow tube, called a proboscis. The butterfly uses the hollow-trunk to suck up the flower nectar on which it feeds (plate 35C). 

Plate 35 A Human Anatomy	35B Animal Bone-pipe	35C Butterfly

(Source35A&B:http://www.google.co.in/search?hl=en&q=Pipe+in+animal+anatomy&bav=on.2,or.r
_gc.r_pw.r_qf.&biw=1328&bih=574&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=By4
nUOfFEM-qrAfIpIC4DQ ; Aug 12, 2012)
35Chttp://www.google.co.in/search?hl=en&q=Pipe+in+animal+anatomy&bav=on.2,or.r_gc.r_pw.r_
qf.&biw=1328&bih=574&um=1&ie=UTF8&tbm=isch&source=og&sa=N&tab=wi&ei=By4nUOfFEM
qrAfIpIC4DQ#um=1&hl=en&tbm=isch&sa=1&q=Pipe+in+butterfly&oq=Pipe+in+butterfly&gs_l=img.
12...32964.35862.6.37759.9.9.0.0.0.0.0.0..0.0...0.0...1c.istPT4Bwb5A&pbx=1&bav=on.2,or.r_gc.r
_pw.r_qf.&fp=acab922e2d9c40ed&biw=1328&bih=574 ; Aug 12, 2012)

Net- ‘A length of open-meshed material made of twine, cord, rope, or something similar, used typically for catching fish or other animals’ In nature spiders create web-net for catching insects. The construction of net is made of porous string-like material. It is oven in a particular matrix and pattern by twisting, knotted or woven at regular intervals. It can secure solid objects. It can separate solids from air or liquids because of its construction pattern. It allows air, water and other liquids to pass through. Spider net (plate 36A) is the most common natural thing is spider net. Net could be flexible or rigid depending on the usage or purpose.