Ixi 



from the egg. They are acquired organs, and are given to the 

 insect during its progress of change. Like the metamorphoses, 

 they are superadded to the original condition of the emhryo or 

 the young within the egg." After some remarks upon classifica- 

 tion founded on metamorphoses, the value of which the author 

 denies (which remarks, however, appear to me to be ill-founded), 

 the author gives the following summary of his views : — 



" 1. The Insecta have a great geological age. 2. The earhest did not 

 undergo metamorphoses, but simply shed their skins. 3. The first forms 

 were wingless Neuroptera or Orthoptera. 4. That in order to meet the 

 influence of changes in external physical conditions during the evolution of 

 varieties of the original forms ; the metamorphoses were acquired. 5. In- 

 complete metamorphoses preceded the complete. 6. Organs of flight were 

 acquired independently of metamorphosis. 7. The kind of metamorphosis 

 depended upon peculiarities in the external conditions, and its determination 

 was defined by law." — 'Nature,' Nov. 14 and 21, 1872. 



The remarkable memoir by M. Balbiani on the generation and 

 embryology of the Aphides has been brought to a close in the 

 * Annales des Sciences Naturelles ' during the past year. 



Metamorphoses. 



The rapid progress in Physical Science making in North 

 America is well illustrated by the publication of a series of 

 publications entitled an ' Illustrated Catalogue of the Museum of 

 Comparative Zoology at Harvard College.' The fifth number of 

 this work, by Louis Cabot, is devoted to the immature states of 

 the Gomphina, a subdivision of the Libellulidse, of which seven- 

 teen species are illustrated, belonging to the genera Hetero- 

 gomphus, Gomphus, Macrogomphus, Progomphus, Gomphoides, 

 Hagenius, Ictinus and Cordulegaster. All the figures represent 

 the insects with well-developed wing-cases, and in the description 

 the immature condition of the insect is described under the name 

 of " Nympha," but the author states that he had seen " 8 nymphse, 

 very young and full grown," of Hagenius brevistylus, and after 

 describing the " Nympha, male," of a species of Ictinus, he adds, 

 " This larva is extremely interesting." The three plates illus- 

 trating this memoir are admirably executed, the whole forming 

 a real contribution to the Science. 



The transformations of several Neuropterous insects have been 

 carefully investigated by Herr Brauer, viz., Micromus, belonging 



K 



