30() Miscellaneous. 



where, as is shown by observations on hving Dipterous larvte and 

 other Arthropoda (Oniscus, Ejjeim), spontaneous obstructions some- 

 times occur in the movement of the corpuscles, and sometimes they 

 stretch themselves to almost three times their ordinary length, and 

 may also break up into fragments. 



As regards the nature of the corpuscles in other respects, their 

 behaviour with various fluids and also when frozen, heated, and 

 electrified, it may be asserted with great probability that they can- 

 not be perfectly identified with the well-known colourless formative 

 constituents of the blood of the Vertebrata (with which they certainly 

 have much in common), and still less with its coloured constituents. 

 As a rule, no differentiation of their substance into a central struc- 

 ture (a nucleus) and a (cortical) layer surrounding it can be observed 

 in the fresh blood-corpuscles ; but the capability of such a differen- 

 tiation must be ascribed to them on both chemical and purely phy- 

 siological grounds. But the author could not detect any true cell- 

 membrane (in Schwann's sense of the word), such as is almost uni- 

 versally ascribed to the blood-corpuscles of insects (as by Landois, 

 "Weissmaun, and Gerstiicker) and other Invertebrata (as by Dr. 

 Hjickel in the crayfish). 



It is especially characteristic of the blood-corpuscles of Insects, 

 and probably of most Arthropoda (Crustacea according to E. Hiickel), 

 that a very variable number of small, frequently dust-like drops of 

 an oleaginous fat are detected upon them. These appear of a more 

 or less intense yellow, but sometimes (pupa of Sphinx lignstri) almost 

 of a hyacinthiue red colour, and appear to indicate a close relation 

 between the blood-corpuscles and the corpus adipjosmn of these ani- 

 mals. The amount of fat in the blood, and especially in the forma- 

 tive constituents suspended therein, may in general determine the 

 colour of the body-fluid to which the name of "blood" is given, 

 and which in most cases is whitish, pale yellowish, or yellowish 

 green. The last-named colour appears especially in decidedly phy- 

 tophagous insects (Acridiidfe, many caterpillars, tfec). Sometimes, 

 however, pigments in the serum, which may also be attached to the 

 corpuscles in the form of little points, are to be regarded as the chief 

 cause of the coloration of the blood of insects. Blood agreeing with 

 that of the Vertebrata, both in its red colour and in the cause of the 

 latter (RoUet), only occurs as an extraordinary rarity (larvae of 

 CMronomns ttc). 



Beside fat, the substance of the blood seems principally to eon- 

 tain globuline (preeipi table by CO-). Both substances not unfre- 

 quently separate in the form of numerous fine acicular crystals, 

 which are usually arranged radially around the central point of the 

 corpuscle. It is less probable, on the contrary, that the contents of 

 a blood- corpuscle become converted into a single crystal. The au- 

 thor found such simple crystals (8-, 4-, and 6-sided tables) similar 

 in composition to snow-crystals. 



The division of the blood-corpuscles, starting from the nucleus, 

 observed by Landois in the larva of Agrotis sec/ctum, and ascribed by 

 him to the blood-corpuscles of insects in general, was not seen with 



