352 TEXT-BOOK OF ENTOMOLOGY 



is not yet known. Grandis observed in living Hydrophilus that the urinary tubes 

 moved, without the muscles seeming to show what caused the motion. Moreover, 

 the cells incessantly changed their form. At a lower temperature such motions 

 ceased. The tracheae, ending freely in the cells, did not anastomose. (Kolbe.) 



The different colors of the tubes (white, yellow, 'red, brown, or green) is due 

 to the hue of the excretions, and is independent of the color of the blood and of 

 the urinary substances held in the secreted matter. 



Schindler found that insects of different stages, collected in winter, differed 

 very much in thejr urinary secretions, the tubes in the adults being entirely 

 empty, while in the larvse they were filled full, so that he concluded that in the 

 former the process of excretion during the winter hibernation is very slow, but 

 in the latter very rapid. 



As to the activity of the urinary vessels the following experiments will throw 

 some light. Tursini fed a Pimelia with fuchsin ; its urinary tubes were conse- 

 quently colored red. Schindler fed insects with indigo-carmine, which was 

 excreted by the urinary tubes ; Kowalevsky arrived at the same results, which 

 seems to prove that these vessels are analogous to the kidneys of vertebrates. 

 Moreover, Schindler injected through the side of the first abdominal segment into 

 the cavity of the body of a Gryllotalpa a concentrated solution of sodium salt of 

 indigotin-disulphonic acid. After one or two hours the external portion of the 

 epithelium of the urinary vessels was stained deep blue, while the inner portion 

 remained of the normal transparency ; the nuclei being for the most part deeply 

 stained. Between one and two days after, the staining matter had not yet 

 wholly passed through the central canal, the surface recently stained still appear- 

 ing light blue. 



The solid contents of the urinary tubes consist partly of crystals, 

 which occur singly in the epithelial cells, or form scattered masses 

 when situated in the central canal. Besides tabular rhombic crys- 

 tals, there occur concretions which contain uric acid, and probably 

 consist of urate of soda, also octahedral crystals of chloride of soda, 

 and quadro-pyramidal crystals of oxalate of lime. Also acicular 

 prisms occur; besides chloride of soda, phosphates, carbonate of 

 lime, oxalate of lime in quantity, leucine, coloring matters, etc. , 

 while the fluid secretion also contains urea (?), uric acid, and abun- 

 dant urates ; uric acid crystals were precipitated by the addition of 

 acetic acid, and by adding hydrochloric acid crystals belonging to 

 the dimetric system were formed. The often numerous spheroidal 

 small granules are biurate of soda and biurate of ammonia. Pale, 

 concentrically banded concretions are leucine pellets. 



According to Kolliker the contents of the urinary vessels x in general are r 

 (1) round granules of urate of soda and urate of ammonia ; (2) oxalate of lime ; 



1 "The contents of the Malpighian tubules may be examined by crushing the part 

 in a drop of dilute acetic acid, or in dilute sulphuric acid (10 per cent). In the first 

 case a cover-slip is placed ou the fluid, and the crystals, which consist of oblique 

 rhombohedrons or derived forms, are usually at once apparent. If sulphuric acid is 

 used, the fluid must be allowed to evaporate. In this case they are much more elon- 

 gated, and usually clustered. The murexide reaction does not give satisfactory indi- 

 cat ions with the tubules of the cockroach." (Miall and Denny, The cockroach, p. 129, 

 footnote.) 



