618 RECORD OF CURRENT RESEARCHES RELATING TO 



Remains of Branchiae in a Libellulid : Smooth Muscle-Fibres 



in Insects.* — Not only has the larva of Eiiphcea — as described f by 

 Dr. Hagen already-^lateral branchife, but even the imago has them. 

 Tbey occur as small cuticular processes on the ventral face of every 

 segment ; on the second segment they are longer and almost free ; in 

 the male they lie beside the genital hooks. Dr. Palmen's assertion to 

 this effect is thus justified. Gills do not occur in the larvte of 

 Mliinocy^ha ; but they occur below the head in the Perlid Dictyopteryx 

 signata. 



A further exception to the conditions obtaining in its congeners is 

 offered by Euplicea, in the presence of numerous smooth, unstripcd 

 muscle-fibres in its caudal gills ; these gills have somewhat the shape 

 of a turnip, and are entirely filled with a pulpy mass consisting of a 

 regular network of sub-hexagonal connective-tissue cells ; they contain 

 fat, and each is penetrated by two stout red tracheal vessels. In 

 longitudinal section they exhibit a great number of smooth cross fibres, 

 and also a series at right angles to these. The fibres are arranged 

 thus in the gill, which has a circular outline with the exception of the 

 lower side which forms a right angle ; from the apex of this angle pro- 

 ceeds a broad bundle, of which the fibres are somewhat distinct, right 

 and left into the gill ; at its middle the fibres are much concentrated ; 

 the upper two-thirds of the gill-cavity are devoid of muscles ; a number 

 of smaller muscles occur in the lower third with the large ones. The 

 only indication of striation in any of these fibres under an immersion 

 power of upwards of 700 diameters was a fine longitudinal lineation 

 near the point of insertion. The physiological action must be that 

 these muscles by contracting compress the two large tracheal vessels 

 which lie nearly in the centre of each, and drive the oxygenated air 

 from the gill into the body, thus meeting the want of a free circulation 

 of blood in the part, which is due to its being filled up with other 

 tissues ; the elasticity of the connective tissue would cause the mass 

 to re-expand. 



A cellular network of such regularity as that of this tissue ap- 

 pears never to have been recorded from the body of an insect 

 before. The cells measure about • 08 mm. in diameter, and their wall 

 less than • 0001 mm. in thickness. The longitudinal striation of the 

 proximal end of the muscles must be due to a series of folds allowing 

 of expansion after the air has been driven into the body. 



Probably similar arrangements will be found in other Calop- 

 teryginfe. 



Metamorphosis of Prosopistoma.| — In August 1878, M. A. 

 Vayssiere, in conjunction with Dr. E. Joly, published a note on the 

 organization of Prosopistoma. Notwithstanding the large number of 

 living individuals they then had at their disposal, they were imable 

 to observe any transformation in these curious insects, and conse- 

 quently were led to accept the view of Mr. MacLachlan, that Proso- 

 pistoma is merely an Ephemerid adapted for a' permanent aquatic 



* ' Zool. Auzeig.,' iii. (18S0) p. 304. t See ante, p. 617. 



t ' Comptes Rcudus,' xc. (1880) p. 1370. 



