182 HALF-AN-HOUR AT 



to submit it at once to them for naming. Many structural details 

 are shown more truthfully in this specimen than in the crushed 

 mounts, the corneal facets are more finely brought out than in any 

 mounted insect I have ever seen ; and there is this peculiarity, 

 that they are as round as if made with a circular punch ! (see Figs. 

 4, 5, PI. XX.) instead of being hexagonal, as is commonly the case, 

 or passing from that into square, as we occasionally find them. 

 And there is a noteworthy thing in the right eye — two corneal 

 facets run together, a thing I have not before met with, and 

 corresponding in its character to the occasional abnormal develop- 

 ments in the eyes of spiders noted by Blackwall. 



Wing of Bombus terrestris.— In the Hymenoptcra the wings 

 consist of a pair called " anterior" and "posterior" on each side. 

 One of the "characters of this order consists in the connection 

 during flight of the two wings on each side of the body, by means 

 of a series of minute hooks along the anterior margin ot the 

 posterior wings, which catch the hinder margins of the anterior 

 wings, thus producing one continuous surlace on each side " 

 (VVestwood, Introduction, Vol. II., p. 76). Analogous contrivan- 

 ces for uniting the wings during flight are met with in some other 

 insects. In the Lepidoptera, where present, these assume the form 

 of a loop and bristles {^Loc. cit., \). 317, and Fig. 102, p. 365). It 

 may be as well to mention that a paper was presented to the 

 Linnsean Society by Miss Staveley, entitled, " Observations on the 

 neuration of the hind wings of Hymenopterous insects, and on 

 the hooks which join the fore and hind wings together in flight," 

 containing much interesting information on the subject, and will 

 be found in the 23rd vol. of their transactions, p. 125, with a plate. 



Spiral Fibres, Petiole of Garden Rhubarb. — This is a very 

 interesting specimen, especially when examined in connection with 

 Dr. Moore's notes upon it. I had no idea my old friend. Dr. 

 Bristowe, had been turning his attention to the development of 

 spiral and pitted tissues in plants, but will take an early opportu- 

 nity of consulting his paper. The late Prof. Henfrey says : — 

 "The mode of formation of the secondary deposits is not clearly 

 known at present. Some imagine them to be precipitated from 

 the cell-sap upon the walls ; others, and apparently with more 

 reason, believe that they are attributable to the agency of the 

 Primordial Utricle, continuing its action after the formation of 

 the primary membrane. Criiyer goes so far as to consider the 

 spiral markings, etc., as dependent on the Rotation currents of 

 the protoplasm. These points recjuire further investigation" 

 (Mic. Die, p. 617). And in special connection with spiral 

 structures, he says : — " It has been stated that the various forms 

 of the open spiral, annular and reticulated deposits are modifica- 



