THE FORMATION OF THE PUPA AND IMAGO. 105 



As in the pupation of Insects, histolytical processes take place, for 

 the tissues have a more or less degenerate appearance (Henking, 

 Xo. 85; Michael, No. 97). According to Gudden (Xo. 81) and 

 Mkgnin (Xo. 96), there is even complete disintegration of the 

 tissues, whereby the resemblance to Insects is increased. Similar 

 processes occur when the nymph changes into the imago, and no 

 doubt have already taken place during the formation of the larva in 

 the egg (deutovum and tritovum). 



In consequence of the withdrawal of the soft parts from the 

 larval integument, the latter appears as a mere envelope around 

 the inner body (Fig. 55 A), all the more so that the empty cases 

 of the limbs usually break off (Fig. 55 A-C). Within the old 

 larval integument another cuticular integument is now formed 

 (Henking); this is the pupal envelope of the Rhyncholophus, and 

 not the definitive chitinous integument of the nymph. This integu- 

 ment (the so-called intermediate integument of Claparede, or 

 apoderma of Henking), in Tromhiclium, is not sac-like as in 

 Rhyncholophus, but forms coverings for the limbs now found on 

 the nymph (Fig. 55 C). Beneath it the chitinous cuticle of the 

 nymph first develops. It appears that the pupa can cast off the 

 larval integument, but does not usually do so, the mature nymph 

 breaking through both integuments when it hatches. 



The statements of Hexkixg as to the intermediate integument appear to us 

 somewhat obscure. According to this writer, the intermediate integument, as 

 well as that formed later, when the nymph changes into the imago and the 

 corresponding " deutovum " membrane are secreted by the isolated cells, which 

 appear beneath the old larval integument or the egg-shell (Fig. 53 A and B, :, 

 Claparede's haemamoebae). The comprehension of these processes is in this 

 way rendered more difficult. Henkixg's statements on this point are not 

 definite, and we are inclined to imagine that the intermediate integument is 

 separated from the subjacent hypodermis, like the larval integument above it. 



The transformation of the nymph into the adult closely 

 resembles that of the larva into the nymph. The latter buries 

 itself and enters upon a resting pupal stage. Beneath the old 

 nymph - integument, an intermediate integument and the new 

 chitinous cuticle again develop (Fig. 56, zh). The limb-cases of 

 the nymph, which, as before, have become empty, arc partially 

 thrown off (Fig. 56); the nymph-integument itself breaks up in 

 some parts, and the perfect animal finally bursts through the 

 integuments that surround it, to start life afresh as imago. It is 

 larger than the nymph, but smaller than a sexually mature imago, 

 though it possesses the organisation of the latter. Sexual maturity 



