1879.] 57 



ligament), for the old skin, when only held by the ligament, may be 

 drawn towards the head of the chrysalis, and still the adhesion is 

 good. It is a curious . circumstance, and one which Mr. Edwards 

 notices also in a letter of the 2nd June,* that this adhesion only takes 

 place at pupation, and even towards the end of it ; and if the skin is 

 drawn down earlier, it will peel off without any attachment to the 

 horns, which will not perhaps have been yet fully developed. What 

 the exact nature of this attachment is I am unable to say. The ex- 

 amination of this region in earlier stages seems to yield the result 

 that the black knob is the earlier developed, and to hint at the hypo- 

 thesis, that the subsequent growth of the white knob may include or 

 nip in a portion of the lining coat of the larva skin in such a way, 

 that it is afterwards held fast.f But the whole history of this question 

 shows how futile is all theorizing that is not supported by accurate 

 and extensive observation. I have seen the ligament, after being 

 drawn out, at first covering the external white knobs and forming a 

 deflexed fold on each side, and then suddenly slipping off these white 

 knobs with the disappearance of the deflexed folds or their absorption 

 into the main body of the ligament, which is still held fast and strained 

 in the groove between the knobs. 



It is to this point, I think, that future attention ought to be di- 

 rected, and I have hastened to communicate these results, however 

 imperfect, in order that time may still be afforded this season for 

 future investigation. I have indicated above my most recent mode of 

 procedure. Good results will also be obtained by dropping the insect 

 into alcohol or boiling water towards the end of puj)ation. I detach 

 the caterpillars when spun up and quiescent, and spread them out on 

 the table before me. Of those pupating in my absence, many will be 

 found with the larva-skin still attached by the ligamentary adhesion, 

 and so will be still available for examination. I should mention, that 

 in letters received from Mr. Edwards in the beginning of June, ob- 

 servations of his on the pupation of Danais Archijjpus are communi- 

 cated, which at first led him to the same view of the nature of the 

 ligament in that insect, namely, that it is " nothing but a part of the 

 skin itself which catches on the knobs, and being elastic, is stretched 

 by the weight and struggles of the chrysalis till it takes a triangular 



* He says : " It is useless, I think, to examine for this membrane until the latter end of the 

 suspending period. One thing is certain, that till late in that stage these knobs do not show 

 themselves, but are soft and white ; but become hard (chitinous) just when they are needed." 

 Mr. E. is speaking here of D. Archippus. 



t Speaking of D. Archippus in a letter of May 30th, Mr. Edwards says : " The knobs, as I say, 

 are at first considerably elongated, or rather stand on end of a long neck ; but, as the chrysalis 

 contracts and the segments swell out, all the neck is buried and only the knob protrudes." 



