614 D. KEILIN 
more developed and of a milky colour. In the larva of 
Ptychoptera contaminata and of a few Eristalids, 
these tubes, at least in their terminal portions, are excep- 
tionally well developed and can be easily seen by transparency 
with the naked eye. Text-fig. 1, which represents a complete 
dissection of the larva of Myiatropa florea, L., shows 
to what extent the calcareous portion of the Malpighian tube 
can be developed in a full-grown larva. In this example the 
posterior pair of Malpighian tubes (p.m.) is composed of two 
short branches of normal structure ; the anterior pair (a.m.), 
on the contrary, is very long, its two branches in their proximal - 
portion are of normal structure and diameter and extend to 
the anterior portion of the body, where they suddenly pass 
into two enormous sacs (¢.p.) with milky contents, which run 
backwards and reach posteriorly the anal segment. These two 
sacs are even thicker than the intestine of the larva ; they are 
very fragile, and the shghtest puncture causes their milky 
contents to flood out. The milky fluid is composed of a thick 
suspension of very small calcareous granules which are almost 
completely soluble in dilute acid, only a small central particle, 
probably of an organic nature, remaining. 
9. CALCOSPHERITES IN THE Fat Bopy. 
In all of the above-mentioned larvae the calcium carbonate 
of the Malpighian tubes appears in the form of crowded small 
cranules suspended in the fluid which fills the lumen of these 
tubes. There are, however, other larvae which contain the 
calcium carbonate in form of calcospherites. ‘The 
latter are enclosed either in the anterior pair of the Malpighian 
tubes or in special cells connected with the fat body. 
The term calcospherite we owe to Harting (7, 1873), who 
was the first to prepare, artificially, calcareous corpuscles 
composed of two substances, mineral and organic. 
He obtained these bodies by precipitating calcium carbonate 
(CaCle+ KeCO3 = CaCog + 2KCI) in a liquid containing organic 
matter (albumen, for instance). The calcareous corpuscles 
thus obtained were elongated or spherical, highly refractive, 
