250 [December, 



From this it would appear that Prof. Eiley's opinions, " based on 

 observations made on species in more than a dozen genera," agree 

 with mine in several points. We are agreed concerning the incorrect- 

 ness of the old account given originally by Reaumur in I73i. He says 

 " I had long become coiiTinced that the popiilar accounts [based on 

 that of Reaumur] were crude and inaccurate." ~\Ve are agreed also 

 that a ligament or membrane is formed out of the lining coat of the 

 larval skin, with attachments as described, which plays an important 

 part in the end of pupation. And I understand also that Prof. Riley 

 has found this ligament likewise in the Siiccincti. We differ, however, 

 as to the co-ordinate importance Prof. Riley gives to what he calls 

 the truclieal and rectal ligaments. As regards the former, as he finally 

 withdraws their claim, nothing more need be said. The chief point of 

 divergence between us is in the importance which Prof. Riley attaches 

 to the so-called rectal ligament, or shed intestinal canal. He goes on 

 to say : " Dissected immediately after suspension and the sub-joint of 

 the larva will be found to be bathed, especially between the legs and 

 around the rectum, in an abundance of translucent, membranous ma- 

 terial. An hour or more after suspension, the end of the forming 

 chrysalis begins to separate from the larval skin, except at the tip of 

 the cremaster. Gradually the skin of the legs and of the whole sub- 

 joint stretches, and, with the stretching, the cremaster elongates, the 

 rectal piece recedes more and more from the larval rectum, and the 

 sustentor ridges diverge more and more from the cremaster, carrying 

 with them, on the sustainers, a part of the soft membrane. If a larva 

 be carefully dissected at this stage, the forming membrane may be 

 raised with the point of a needle, and stretched so as to show its con- 

 nection with the rectal ligament ; or it may lifted entirely from the 

 retainers, when, by its elasticity, it contracts and becomes more or 

 less fully absorbed in the rectal ligament. It is at this stage that the 

 strength of the latter may be fully tested, and if the chrysalis, flayed 

 from the larval skin and freed from the retaining membrane, be 

 grasped in the neighbourhood of the rectum, so as to supply the 

 natural holding powers of the sphincter m.uscles,* the rectal ligament 

 will sustain, as I have abundantly proved, at least ten or twelve times 

 the weight of the chrysalis, while it will support, if held by the larval 

 skin, sevei'al times the weight of the chiysalis before separating 

 therefrom." 



For my own part I have never been able to see that the shed in- 

 testinal canal has any influence on the suspension of the chrysalis 



* Are these sphincter muscles supposed to be in the cast-off larval skin ?-J. A. O. 



