MALARIA EXPEDITION TO NIGERIA 71 
rossii on the seventeenth and eighteenth days of cultivation. ' The young filariae are 
found in the tissues of the thorax, in those of the head and neck, and in fewer 
numbers in those of the abdomen. The tissues of the head are examined by cutting 
through the neck By carefully dissecting with needles the tissues or 
the head, and separating the parts of the proboscis, two or three filariae will almost 
invariably be found in this situation, and I have lately on two occasions found a 
filaria lying stretched out lengthwise partly within the tissues of the labrum of the 
proboscis, the remainder of its body being curled up in the tissues of the head. 
Without dissecting up the tissues of the labrum these filariae could be plainly seen 
with a ^ inch objective through its fairly transparent tissue indulging in sinuous 
undulatory movements, and a very little manipulation with the needles sufficed to 
free the filariae when their movements changed from the snake-like undulatory 
character to the vigorous purposeless lashing and twisting which are characteristic of 
the final stage of the metamorphosis of the parasites in the mosquito. In the 
diagram I have shown the appearance of the filaria as it lies partly within the labrum. 
The young filariae in the final stage are from -5- to ^ of an inch in 
length, and ^ o inch in greatest breadth. It tapers towards the head and tail ; the 
latter has three projections which can be spread out or drawn closely together in 
the animal's movements. The head end is rounded, and the mouth which is very 
extensile can be pushed out to form a little cone-like projection which sways from 
side to side, and is drawn in and pushed out as if searching for food. The filariae 
have an alimentary canal which at a somewhat earlier stage can be seen to be very 
freely moveable within the animal's body, and to be of varying shape in different 
parts of its course. Near the anus it is wide, and then narrows gradually to open at 
a short distance from the tail. On each side of the alimentary canal near the head, 
and again at a point about the middle of the body, the protoplasm is differentiated 
into other organs — probably reproductive.' 
On August 4, 1 900, as a result of some experiments which we had been 
carrying on as opportunities presented, during the time we were in Southern 
Nigeria, we were able to cable home that a living filaria had been found in the proboscis 
of Anopheles costalis. Previous to this several attempts had been made by us to cultivate 
both F. nocturna and F. diurna in mosquitoes of both genera, Culex and Anopheles, but 
without success. In this experiment with F. nocturna we were however successful. 
We had on several occasions previously noticed that large filariae were to be seen in 
the head of mosquitoes. The mosquitoes were fed on two occasions on blood 
containing embryos — July 18 and July 20, and in order to keep them alive for a 
period they had occasionally been fed on blood containing no embryos. On August 4 
only five Anopheles of the batch remained, two of them being dead on the water. 
One of these on dissection proved negative. In the other, in the proboscis and near 
a trachea in the labium of that organ was a long thin filaria. In the thorax of this 
