CALCIUM CARBONATE IN DIPTEROUS LARVAL 625 
to exist in several Crustacea, e.g. Gonoplax rhomboides 
and others. According to this author, several Crustacea, 
Collapa or Ebalia, for instance, which live upon the 
Red algae, in a medium rich in ammoniacal alkali, do not 
eliminate the CO, derived from their respiration ; they retain 
it to neutralize the ammonia which reaches their blood and 
tissues. 
We know, on the other hand, that in insects the respiratory 
function differs markedly from that of other groups of animals. 
In insects oxygen is supplied to the tissues by means of 
a highly developed ramified system of tubules—the tracheae, 
while the carbon dioxide is given up by the same tissues to 
the perivisceral fluid and thence eliminated through the 
whole surface of the body. 
It is possible that a part of this CO, is neutralized in the 
blood or perivisceral fluid; but at present this is purely 
hypothetical and needs verification by proper experimental 
inquiry. It indicates, however, that it would be of great 
interest to determine correctly the respiratory quotient of an 
insect larva which, like Eristalis, Ptychoptera, and 
others living in putrefying media, contains within its body 
a large quantity of calcium carbonate. 
6. CONCLUSIONS. 
1. The larvae of a great number of Diptera, parasitic, phyto- 
phagous, or living in putrefying substances, contain in their 
bodies a large quantity of stored calcium carbonate. 
2. The latter is present in the Malpighian tubes or in special 
cells connected with the fat body. 
3. Calcium carbonate is stored either in form of a thick sus- 
pension of small granules (in the Malpighian tubes) or in the 
form of calcospherites (in the Malpighian tubes or the fat 
body). 
4. Calcium carbonate remains wholly or partly in the body 
of the larva when the latter passes into the pupal stage, but 
disappears by the time the adult stage is reached. 
5. During the first days of metamorphosis the caleium 
Tt?2 
