The secreting cells never show this change, although they may become atrophied or destroyed by the pressure and the disturbance of nutrition brought about by the swollen condition of the capillary walls.
In the more primitive forms the appendage of every post-oral somite has a gnathobase and two rami; in higher specialized forms the gnathobases may be atrophied in every appendage, even in the first post-oral.
Finally, the original symmetry of the circumanal complex vanishes; the anus leaves the centre of the pallial cavity and passes towards the right side (left side in sinistral forms); the organs of this side become atrophied and disappear.
A prae-genital somite is often present either in a reduced condition forming a waist (Pedipalpi, Araneae, Palpigradi) or as a full-sized tergal plate (Pseudoscorpiones); in some it is entirely atrophied (Solifugae, Holosomata, and Rhynchostomi).
Placuna; byssus atrophied in adult.
P. Sladen, who divided the Euasterida into two orders: (I) Phanerozonia, with marginals large and highly developed, the supero-marginals and inferomarginals contiguous, with papulae confined to the dorsal surface, with ambulacrals well spaced and usually broad, adambulacrals prominent in the mouth-skeleton, with pedicellariae sessile; (2) Cryptozonia, with marginals inconspicuous and somewhat atrophied in the adult, the supero-marginals separated from the inferomarginals by intercalated plates, with papulae distributed over the whole body, with ambulacrals crowded and narrow, either ambulacrals or adambulacrals prominent in the mouth-skeleton, with pedicellariae stalked or sessile.
On the other hand, when it becomes atrophied the circulation becomes feeble, the face heavy and dull, the patient suffers from cold, the features glow lumpish, mental processes become sluggish, and bodily vigour diminishes.
Top columnal a persistent proximale, often fusing with IBB, which are frequently atrophied in the adult.
In certain derivative forms constituting the family Pallenidae, however, the appendages of the 2nd pair are either rudimentary or atrophied altogether.
An ectodemic invagination forms a large mucous gland on the foot, which is more or less atrophied in adult life.