t6 Miscellaneous. 



this insect, believing it to form the type of a genus previously un- 

 known ; he afterwards, however, recognised it as belonging to the 

 genus Anomma, Shuck., described in 1840. He seems to think, how- 

 ever, that the latter name comes so near that of Anommatus, which 

 was appropriated in 1836 by Wesmael for a genus of Coleoptera, that 

 it ought to be suppressed, in which case his name would be substi- 

 tuted for that given by Shuckard to this genus. — Bericht uher die 

 Verh. der Naturf. Gesellsch. zu Basel, x. 1852, p. 175. 



On a new Muscle-element in the Thoracic Muscles of Insects. 

 By Dr. Burnett. 



Aubert* states that he has found an entirely new form of muscle- 

 element in the Libellulidce ; this consists of flat, primitive, muscular 

 bands occurring only in the thorax, and which by means of a pitcher- 

 shaped {becherformigen) apparatus move the wings. 



The following are his conclusions on this subject : — 



" 1 . The comparatively very large muscles of those insects which 

 fly with a buzzing so and, separate, when fresh, into fine, transversely 

 striated fibres. ^ 



" 2. The fibres are the primitive muscular fibrillae. 



"3. Between the fibrillse there is a granular mass, the use of which 

 is unknown. 



"4. AH other muscles when fresh present no appearances of this 

 kind. 



"5. The Libellulidce have in the thorax primitive muscular bands.^ 



" 6. The elements of the muscles are little cakes or cylinders which 

 are applied together, forming the fibrillse. 



" 7. During contraction the fibrillse thicken, and the striae are ap- 

 proximated." 



These results have been confirmed by my own experience, for the 

 thoracic muscles of insects have long been to me beautiful objects for 

 the study of the histological elements of muscular tissues. It is a 

 form of this tissue particularly to be recommended for the study of 

 the intimate sarcous elements. The fibrillse readily separate into the 

 discs of which they are composed, and the whole field is then filled 

 with these last floating freely about. But it is a question if these 

 primitive fibrillse, which are here so distinct, are not the products of 

 definite cleavages of primitive muscular fibres. In studying them 

 carefully with a power of 800 to 1000, we have been able to detect 

 no remains of their early formative conditions. Furthermore, we 

 know that the muscular fibre is the primitive embryological element 

 of this tissue. It therefore appears to us probable that this pecu- 

 liarity of the thoracic muscles of insects is due simply to readiness 

 for cleavage, and which may be subservient to their rapid and deli- 

 cate action. 



Another point which we have noticed, and which Aubert also has 

 alluded to, is the singular spiral aspect which these fibrillse some- 

 times assume from an apparently irregular movement in their con- 



* " Ueber die eigenthiimliche Structur der Thorax muskeln der Insekten,'* 

 in Siebold and Kolliker's Zeitsch. fur Zool. iv. 1853, p. 388, taf. 15. 



