58 SUMMARY OP CURRENT RESEARCHES RELATING TO 



the nerve branches like a tree, as in Vertebrates. He describes the 

 destruction of the muscular tissue, &c., during the metamorphosis, 

 and its solution in the body-cavity. The integuments of the adult 

 are not derived from those of the larva, but from " imaginal discs," 

 produced during the metamorphosis. Each muscular fibre is pro- 

 duced from cells, which become the nuclei, imbedded in a homogeneous 

 matrix, which becomes contractile. 



M. Viallanes has traced the nerve from the facet of the eye into 

 the brain : he shows that all the parts of the adult eye are enclosed 

 in the larva within the brain. 



Origin of the Elements in the Insect Ovary.* — Dr. E. Korschelt 

 contributes a somewhat lengthy paper upon this subject, which is 

 partly a criticism of the work of other observers, and partly a state- 

 ment of the author's own results; his investigations deal with a 

 number of types which are severally described; the general con- 

 clusion arrived at is contrary to that of Will, and may be stated as 

 follows : in certain insects the cell-elements of the egg-tubes, that is, 

 the epithelium and the nutritive cells, arise by direct metamorphosis 

 of the elements of the terminal chamber, and may be followed into 

 the indifferent tissue of the terminal thread. 



Metamorphosis and Anatomy of the Male Aspidiotus Nerii.f— 

 Herr 0. Schmidt distinguishes five periods in the metamorphosis of 

 this insect, defining two larval and two chrysalis stages. He 

 describes the anatomy of the alimentary, respiratory, nervous, 

 muscular, and reproductive systems, noting both in regard to anatomy 

 and metamorphosis the differences between male and female. His 

 anatomical results, which are essentially corroboratory of those of 

 Tozzetti, do not contain any new facts of general interest. The 

 spermatogenesis is described as consisting of the division of the 

 hexagonal testicular cells into five or six " spermatoblasts," from each 

 of which a bundle of spermatozoa is formed. 



Vision of Insects. | — M. F. Plateau communicates a preliminary 

 note of experiments made in order to prove whether or not insects 

 can really distinguish by vision the form of external objects. The old 

 mosaic theory of J. Miiller having been shown by Exner to be, 

 on anatomical and physical grounds, untenable, M. Plateau has 

 endeavoured to settle the question experimentally. 



In a darkened room, with two differently shaped, but approximately 

 equal, light openings, one square and open, the other subdivided into 

 a number of small holes, and therefore of more difficult egress, he 

 observed the choices of opening made by insects flying from the 

 other end of the room. Careful practical provisions were made to 

 eliminate error ; the light intensity of the two openings was as far as 

 possible equalized or else noted ; no external objects such as trees, &c., 

 were within view, &c. The room must not be darkened beyond the 

 limit at which ordinary type ceases to be readable, else the insects 



* Zool. Anzeig., viii. (1885) pp. 581-6 and 599-605, 

 + Arch. f. Naturgesch., li. (1885) pp. 169-200 (2 pis.). 

 J Bull. Acad. R. Sci. Belg., x. (1885) pp. 231-50. 



