Linnaan Society. 147 



in Melbe, showing the mode in which the changes in the structure 

 of the mandibles are effected, and pointing out corresponding changes 

 in the function of the parts ; noticing also that change in structure 

 during the growth of an animal usually precedes change in the 

 function of an organ, — a circumstance which leads to the inference 

 that function is closely dependent on speeial structure. 



The secondary changes during the development of Articulata, the 

 metamorphoses, are effected, not by the tegument itself, but by the 

 agency of structures connected with the tegument — the muscles. The 

 author stated that we are entirely ignorant of the secret cause which 

 first excites the muscles, at a definite period of growth, into action 

 in effecting these changes ; but suggested that it is in the expansive 

 and contractile forms of growth in the tissues themselves. All that 

 is known with certainty is, that it is through the direct agency of 

 the muscles that the form of body of the insect is rapidly altered at 

 the period of the metamorphoses, and that the operation of these is 

 accelerated or retarded by physical influences. The mode in which 

 the muscles operate in effecting the changes was then pointed out, 

 and the altered proportions of different parts of the body after the 

 change was shown to depend on the greater or less extent to which 

 the contraction of the muscles of different segments is carried. 



The result of these altered proportions in the tegument of an in- 

 sect that is changing to the form of pupa or nymph, as in Melbe, is 

 a rapid re-induction of the forces of growth in the appendages, the 

 future wings and legs, which become greatly elongated, at and im- 

 mediately after the change, These alterations of form are accom- 

 panied as a last result by changes in the intimate structure of the 

 tegument, a consolidation of a large portion of it, and the formation 

 of the dermo-skeleton of the imago. 



May 2. — The Lord Bishop of Norwich, President, in the Chair. 



Read a memoir " On the Anatomy and affinities of Pteronarcys 

 regalis, Newm." By George Newport, Esq., F.R.S., F.L.S. &c. &c. 



Mr. Newport commenced by stating that the existence of a 

 winged insect with branchial organs for respiration is so anomalous 

 a condition of life, that himself as well as others at first regarded 

 the specimen he had obtained rather as an accidental instance of 

 incomplete development than a normal condition. He found how- 

 ever, on comparing his specimen, preserved in spirit, with other dried 

 specimens in the cabinets of the British Museum, that this was not 

 the case, as evidences of branchiae are to be found in the whole of 

 the dried specimens of the genus in that collection. 



Having waited some years since obtaining this specimen, in hopes 

 of receiving others for the purpose of dissection, the author has now 

 made a careful examination of the insect. He described the forms 

 of branchiae in different genera of Neuroptera, and pointed out that 

 the peculiarity of Pteronarcys consists in its possessing in its winged 

 state, both branchiae for aquatic respiration and spiracles for the 

 direct respiration of air. 



He then described the branchiae, their connexion with the respi- 



10* 



