E. E. Atkin and A. Bacot 
515 
larvae hatched in some of these tubes, but made still slower progress than did those 
with charcoal, behaving as did the larvae in sterile peptone water or peptone broth, 
generally dying in their first instar and but very exceptionally surviving to the third. 
2 % solution of yeast extract with charcoal added. After 50 days in one tube 
(No. 30) there were several larvae in the third instar and at least one in the fourth; 
1 had pupated but the pupa died. All the larvae were lank and slender and had 
failed to develop the fat bodies which, towards the close of the larval life, become 
rather obvious owing to the opaque white appearance that they give to the larvae. 
The second tube (No. 31) contained 4 larvae in their fourth instar, all deficient 
in fat deposits. 
One tube (No. 32) contained a single weakly looking fourth instar larva; the 
emainder were dead. 
Another (No. 33) contained 4 fourth instar larvae, aU deficient in fat. 
In tube No. 34 none of the larvae had got past the third skin. By the 56th day 
the larvae in tubes 31 and 32 were dead. 
One larva was living in tube 30 on the 76th day, but died before the 95th day. 
In tube No. 33 two larvae lived until the 76th day and one until the 123rd day, 
when it died. In tube No. 34 two larvae lived until the 76th day; between the 
76th and 95th days several larvae hatched from dormant eggs in this tube. Tests 
showed that sterility wais stiU maintained ; by the 107th day all the recently emerged 
larvae were dead except one, and this had passed the first moult; two died between 
the 107th and 123rd day. Between the 123rd and 143rd day moulds developed in 
the tube and the last surviving larva died. 
Expekiment XVII. 
A further series of tubes containing a 3 % solution of autolyzed extract of 
brewers’ yeast in distilled water, some with and others without charcoal, were 
prepajed. 
23 days from start. 
No. 51, sterile, larvae. Slender in second or third instar. 
No. 52 ,, ,, Slender in third or fourth instar. 
No. 53 „ „ Great disparity of growth in all instars from first to 
fourth skin; aU slender. 
No. 54 „ „ Slender in second or third instar. 
No. 55 „ „ Great disparity of growth in aU instars from first to 
fourth skin; all slender. 
Tubes, loith charcoal, 56 and 57. 
No. 56, a mould grew, the larvae had grown steadily and were in fourth instar. 
No. 57, sterile larvae show slow but healthy growth, are rather more robust 
than those in the tubes without charcoal, but are only in second 
and third skin. 
40 days from start. 
Nos. 51 to 55 without charcoal. No appreciable progress in the last 17 days. 
Nos. 56 and 57 with charcoal. 
No. 56, larvae have aU died without pupating. 
No. 57, no appreciable progress. 
Parasitology ix 
34 
