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whole organ, which, as we know, becomes snb-obsolete in the 

 imago state of so many Lepidoptera. The ilium and colon are 

 more particularly serviceable, and the ligament holds with such 

 force around the anus of the cast larval skin that it cannot well 

 be severed. The rectum of the nascent chrysalis draws this in 

 or lets it go by peristaltic action of the sphincter muscles, the 

 whole ligament being drawn out as soon as the hooks of the 

 cremaster reach the silk. In addition to this rectal ligament, 

 which is of a reddish color, and which Prof. Riley considers 

 the principal suspensor, there are two lateral ligaments, also 

 quite long and strong, and of the color of the skin, which serve 

 as auxiliaries. These are the shed linings of the tracheae issu- 

 ing from the last or ninth pair of spiracles, which in the chrysalis 

 become closed or blind. These ligaments may be called the 

 tracheal ligaments, and seem to be somewhat specialized to aid 

 in this important act. Lastly, there is the membrane proper 

 referred to by Dr. Osborne, which is, virtually, but the anal 

 portion of tie inner lining of the skin itself, or corium, caught 

 upon the knobs at the end of the ridges which usually form the 

 ventral part of the cremaster. It consists chiefly of the skin 

 that lines the region of the rectum and the anal prolegs, and 

 takes on a more or less bifurcated form from the pulling power 

 of the knobs during the act of withdrawal from the larval skin. 

 The ligaments Prof. Riley considers constant physiological fac- 

 tors in the problem, most necessary in those species which have 

 the knobs imperfectly developed ; acting even during the larval 

 molts, and so holding the shed skin of lepidopterous larvae that 

 it is worked to the anus in a shriveled mass, as a stocking is 

 pushed to the toes ; whereas most other insects, especially those 

 in which the metamorphosis is incomplete and the change in the 

 intestinal canal but slight, crawl out of the exuviae rather than 

 work them oflP, the anal parts not being held within the end of 

 the casting skin, but really being the first parts detached^ 

 The membrane is a purely mechanical factor, and may not 

 always be properly caught and drawn out. It may also be 

 severed without necessarily causing the chrysalis to drop. Yet 

 that it is an important aid to the rising of the chrysalis, there 

 cannot be much doubt ; and Pi-of Riley finds, in the chrysalis of 



