OCT 10 1922 
PSYCHE 
VOL. XXIX. AUGUST 1922 No. 4 
POSSIBLE PEDOGENESIS IN THE BLOW-FLY, Calliphora 
erythrocephala MEIGEN. 
By G. H. Parker. 
Zoological Laboratory, Harvard University. 
In the early autumn of 1918 I prepared a number of cultures 
of larvae of the common blow-fly, Calliphora erythrocephala, and 
in several of these cultures the numbers of maggots seemed to 
exceed considerably the numbers of eggs that had been intro- 
duced. This aroused the suspicion that some unusual form of 
multiplication such as polyembryony or pedogenesis was oc- 
curing and to test this definite experiments were attempted. 
On November 25, 1918, thirty bottles closed with aluminum 
caps through each of which a minute hole had been punched, 
were supplied with small pieces of fish-meat carefully inspected 
to see that they carried no fly eggs. In each of twenty of these 
bottles a single blow-fly egg was placed, ten bottles having been 
retained as checks. On December 9, 1918, all these bottles were 
carefully examined. Seven of the infected bottles contained no 
maggots, ten contained each one maggot, one contained two 
maggots, another three, and a third four. One of the check 
bottles, however, contained nine small maggots showing that 
the procedure that had been followed was defective. Either un- 
seen eggs had been accidentally introduced with the meat, or 
flies had slipped eggs into the bottle through the small hole in 
the cap. Hence the increased numbers in several of the infected 
bottles could not be said to be due to multiplication within the 
bottle itself and this type of test was, therefore, abandoned. 
In the spring of 1919, with the return of the flies, a new 
procedure was employed. Fifty clean quart jars were prepared 
by pouring into them enough coarse sand to cover their bottoms. 
This sand had previously been sterilized by baking. Into each 
