196 Mr. B. T. Lowne on 
In support of these statements, I will briefly bring one 
or two facts before you. Certain monstrous conditions 
in Vertebrates, in which almost all the parts of the body 
are doubled, are nearly, if not always, female; whilst in 
insects the male is sometimes developed agamically, as 
in the bee; and the males are usually smaller than the 
females. 
Dr. H. Landois* published some very remarkable facts, 
which appear to me to have received considerably less 
attention than they deserve, owing to the flood of con- 
troversy, which originated in certain mistakes made by 
the author, and which led him to disbelieve in Partho- 
genesis. 
Dr. Landois stated, that whole broods of some insects 
are often either entirely composed of males or females 
only. He affirmed that ill-fed larvee always produced 
males, whilst well-fed ones usually produced females. In 
this there was clearly some error of observation, as it is 
a well-known fact, that the sex may be determined from 
an examination of the embryo long before it leaves the 
ege. 
On the other hand, I am not inclined to look upon Dr. 
Landois’ statement as altogether incorrect. The only 
insect I have ever bred in large numbers is the blow-fly, 
and I found that nearly all the insects bred from the 
large well-fed larvee bought at the fishing-tackle shops 
were female, whilst ill-fed small larvee have usually pro- 
duced males. There may be an error in this observation, 
and it has occurred to me that it is possible the breeders 
of the maggots may pick out the largest larvee, which 
are the females, for their best customers, the large shops: 
selling the smaller male larvee to the smaller tradesmen. 
Still I cannot find that this is actually the case. From 
the large number of pupee that always died, usually more 
than half, I am rather inclined to believe that a large 
supply of highly nutritive food may act injuriously on 
the male larve, especially if they are stimulated to feed 
by a higher temperature than the normal one, by causing 
an abnormal development, of the fat bodies for instance, 
at the expense of the structures destined to form the 
pupa. It is easy to understand why too little food would 
produce males only, as the females would perish before 
arriving at maturity. 
* ¢ Zeitschrift ftir wissensch. Zool.,’ Band 17, s. 375. 
