376 Professor Westwood [May 24, 



gourmand, after his dinner, unbuttons his waistcoat and takes liis nap. 

 Just the same is done by insects. The " Museum beetle," for example, 

 having eaten all it wants, splits open its waistcoat along the back, and 

 goes to sleep as a pupa, creeping out of its covering when it assumes 

 the final state. 



The relations of the Crustacea and Arachnida with the true insects 

 was then dwelt upon, and it was stated that since the days of Linnaeus 

 (when it was supposed that the latter only underwent transformations) 

 it had been discovered that equally striking changes of form are 

 undergone by many of the wingless articulated animals having arti- 

 culated legs. Even the barnacle (after the rejection of the old fancy 

 that it was transformed into a goose), which had been supposed to be 

 a mollusc, had been discovered to be subject to real transformations, 

 its earliest state proving its crustaceous character, being extremely 

 active and furnished with natatory limbs. These changes, first dis- 

 covered by Mr. Yaughan Thompson, had been fully proved by Mr. 

 Darwin, whose monograph on the Cirrhopoda was one of the most 

 masterly works ever published. In like manner Mr. Vaughan 

 Thompson was also the discoverer of the changes to which most of 

 the true Crustacea are subject, the eggs of crabs, shrimps, &c., 

 being developed into minute transparent animals, unlike their parents, 

 with long spines projecting from the front and sides of their shell, and 

 which swim about by the assistance of a long jointed tail and natatory 

 limbs, which, in a later state, become reduced in size and altered in 

 function, forming the foot-jaws of the adult animals, the real locomo- 

 tive limbs being then developed, although previously they only existed 

 in a rudimentary state beneath the carapace of the young animal. 



The centipedes and millepedes, forming the class Myriapoda, were 

 also subject to a series of changes, by which additional segments were 

 from time to time developed out of the penultimate ring of the body, 

 to which the name of the germinal segment had been applied. At 

 each moulting, also, a fixed number of additional legs were developed 

 in double pairs, attached to those segments, which had been produced at 

 a previous moulting. For the most accurate knowledge of the changes 

 of this class we are indebted to the labours of the late Mr. George 

 Newport, whose early death was much to be lamented as a great loss 

 to science. 



The speaker then passed on to the true Insecta, which in their full 

 development acquired wings. The great consumption of material here 

 takes place in the larva state ; the perfect insects are rarely voracious. 

 The gnat, it is true, stings, and takes food in the shape of blood ex- 

 tracted from its victim, and so some others ; but many perfect insects 

 have only rudimental mouths, and all their sustenance has been taken 

 in during their antecedent caterpillar state. The larvae hatched from 

 one ounce of silkworms' eggs, require 1609^ lbs. weight of leaves for 

 their food ; but as their digestive powers are not so strong as those of 

 the higher animals, only about 771 lbs. weight of the pure leaves are 

 digested, from which 120 lbs. of silk cocoons are produced. A single 



